WO2024070137A1 - リチウムイオン二次電池用正極材料及びその製造方法、リチウムイオン二次電池用正極、ならびにリチウムイオン二次電池 - Google Patents

リチウムイオン二次電池用正極材料及びその製造方法、リチウムイオン二次電池用正極、ならびにリチウムイオン二次電池 Download PDF

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WO2024070137A1
WO2024070137A1 PCT/JP2023/025770 JP2023025770W WO2024070137A1 WO 2024070137 A1 WO2024070137 A1 WO 2024070137A1 JP 2023025770 W JP2023025770 W JP 2023025770W WO 2024070137 A1 WO2024070137 A1 WO 2024070137A1
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positive electrode
ion secondary
secondary battery
electrode material
lithium
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English (en)
French (fr)
Japanese (ja)
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竜太 山屋
昌平 水沼
暁 忍足
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Sumitomo Metal Mining Co Ltd
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Sumitomo Metal Mining Co Ltd
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Priority to JP2024549768A priority Critical patent/JPWO2024070137A1/ja
Priority to EP23871381.2A priority patent/EP4597626A4/en
Priority to CN202380068259.7A priority patent/CN119948647A/zh
Priority to US19/115,317 priority patent/US20260112611A1/en
Publication of WO2024070137A1 publication Critical patent/WO2024070137A1/ja
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    • 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
    • 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
    • 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
    • H01M4/13—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
    • H01M4/58—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
    • H01M4/36—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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/77—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by unit-cell parameters, atom positions or structure diagrams
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive electrode material for lithium ion secondary batteries and a manufacturing method thereof, a positive electrode for lithium ion secondary batteries, and a lithium ion secondary battery.
  • Lithium-ion secondary batteries have higher energy density and power density than lead batteries and nickel-metal hydride batteries, and are used for a variety of purposes, including small electronic devices such as smartphones, home backup power sources, and power tools.
  • small electronic devices such as smartphones, home backup power sources, and power tools.
  • large-capacity lithium-ion secondary batteries are being put into practical use for use in electric vehicles and other vehicles, and for storing renewable energy such as solar and wind power generation.
  • the lithium ion secondary battery includes at least a positive electrode, a negative electrode, and an electrolyte.
  • the electrode material constituting the positive electrode is a lithium metal composite oxide having a property of reversibly inserting and removing lithium ions, such as lithium cobalt oxide (LiCoO 2 ) or lithium manganese oxide (LiMn 2 O 4 ), which is an oxide-based positive electrode material, or lithium iron phosphate (LiFePO 4 ), which is an olivine-based positive electrode material. Improvements are being considered from various perspectives, such as increasing the capacity of the battery, extending its life, improving its safety, and reducing its cost.
  • the lithium iron phosphate (LiFePO 4 ) is a material that can be easily manufactured at low cost because it uses iron, which is an abundant and inexpensive resource.
  • lithium iron phosphate has excellent properties that are not available in oxide-based positive electrode materials such as lithium cobalt oxide, such as excellent safety due to the strong covalent bond between phosphorus and oxygen, which prevents oxygen release at high temperatures.
  • lithium iron phosphate has an olivine structure, which means that it has low Li-ion diffusivity and electronic conductivity, resulting in problems with input/output characteristics that are inferior to oxide-based positive electrode materials. This difference in characteristics becomes more pronounced when the operating temperature of the battery is low, so lithium iron phosphate with an olivine structure has been considered unsuitable for in-vehicle applications such as electric vehicles and hybrid vehicles, which require high input/output characteristics, especially at low temperatures.
  • Patent Document 1 proposes an electrode material represented by the composition formula LiFe1-xMxPO4 ( M is one or more elements selected from Mg, Ca, Sr, Ba, Sc, Y, Zn, Al, Ga, In, Si and rare earth elements, 0 ⁇ x ⁇ 0.5).
  • Lithium iron phosphate has a problem in that the volume of the crystals changes significantly during charge and discharge reactions, which causes structural defects such as cracks and fractures in the active material particles, resulting in reduced charge and discharge capacity and cycle characteristics.
  • Patent Document 1 claims that it is possible to provide a lithium secondary battery with a large discharge capacity, excellent cycle stability, and a long life.
  • the electrode material proposed in Patent Document 1 focuses on the phase transition rate of the two-phase coexistence reaction of Li1 -yFePO4 and FePO4 , and claims that the phase transition rate is increased by the addition of an element, and the volume change is also reduced, thereby reducing polarization during charge and discharge, resulting in a high capacity and a small capacity decrease due to charge and discharge cycles.
  • one aspect of the present invention aims to provide a positive electrode material containing lithium iron phosphate that has excellent cycle characteristics and high input/output characteristics when used as a positive electrode for a lithium ion secondary battery, a method for producing the same, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery.
  • a positive electrode material for a lithium ion secondary battery in which the rate of change in lattice area of the b-axis-c-axis plane of the positive electrode material before charging and after full charging ([(lattice area before charging-
  • the positive electrode material for a lithium ion secondary battery described in ⁇ 1> in which the rate of change in lattice volume of the positive electrode material before charging and after full charging ([(lattice volume before charging - lattice volume after full charging) / volume before charging] x 100) is 4.90% or more and 6.06% or less.
  • the positive electrode material for a lithium ion secondary battery according to ⁇ 1> or ⁇ 2> wherein the positive electrode material has a tap density of 1.1 g/cm3 or more , an NMP absorption amount of 40 mL/100 g or less, and a green density of 2.4 g/cm3 or more when the positive electrode material is compressed under a pressure of 16 kN into a circle having a diameter of 20 mm.
  • a method for producing a positive electrode material for a lithium ion secondary battery according to ⁇ 1> or ⁇ 2> a crystallization step of obtaining crystallized particles by a crystallization reaction using a metal source having a valence of divalent, trivalent, or both, and a phosphate source; a water washing step of washing the crystallized particles with water and drying them to obtain a precursor of the positive electrode active material; a mixing step of mixing the precursor of the positive electrode active material, a lithium source, and a carbon source to obtain a raw material mixture; a calcination step of calcining the raw material mixture in a non-oxidizing atmosphere to obtain a positive electrode material containing the positive electrode active material; Equipped with the precursor of the positive electrode active material has a ratio of the amount of P to the total of Fe, Mg, and a metal element A (P/(Fe+Mg+A)) of 0.95 or more and 1.03 or less.
  • ⁇ 6> The method for producing a positive electrode material for a lithium ion secondary battery according to ⁇ 5>, wherein the precursor of the positive electrode active material has a specific surface area of 7.0 m 2 /g or more and 12.0 m 2 /g or less, and a particle diameter at a cumulative percentage of 50% (D50) in a cumulative particle size distribution of 0.5 ⁇ m or more and 5.0 ⁇ m or less.
  • a positive electrode for a lithium ion secondary battery comprising an aluminum current collector and a positive electrode mixture layer formed on the aluminum current collector, A positive electrode for a lithium ion secondary battery, wherein the positive electrode mixture layer contains the positive electrode material for a lithium ion secondary battery according to claim 1 or 2.
  • a lithium ion secondary battery having at least a positive electrode, a negative electrode, and an electrolyte,
  • the positive electrode is the positive electrode for lithium ion secondary batteries according to claim 7 .
  • a positive electrode material containing lithium iron phosphate that, when used as a positive electrode of a lithium ion secondary battery, has excellent cycle characteristics and high input/output characteristics, a method for producing the same, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery.
  • FIG. 2 is a schematic diagram showing a cross-sectional configuration of a laminate type battery produced in the examples and comparative examples.
  • the positive electrode material for a lithium ion secondary battery of this embodiment contains lithium iron phosphate as a positive electrode active material, and has a structure having a conductive carbonaceous coating for improving the conductivity of the positive electrode material.
  • the positive electrode material for lithium ion secondary batteries may be simply referred to as a "positive electrode material.”
  • lithium iron phosphate may be simply referred to as "LFP.”
  • Li ions are desorbed and inserted at the two-layer interface between the Li-containing layer (LiFePO 4 ) and the Li-releasing layer (FePO 4 ) during charge-discharge reactions.
  • the two-layer interface refers to the b-axis-c-axis plane.
  • the plane parallel to the b-axis and c-axis is referred to as the "b-axis-c-axis plane” or "bc plane.” If the difference in lattice area at this two-layer interface, that is, the difference in lattice area between the Li-containing layer and the Li-releasing layer, becomes large, it becomes a barrier to the Li ion desorption reaction, and the larger the difference in lattice area, the more the Li ion desorption reaction is hindered, resulting in a deterioration in charge-discharge characteristics.
  • the inventors have found that the input/output characteristics of a lithium ion secondary battery are affected by the difference in lattice area that occurs in the bc plane where Li ions are inserted and removed due to charge/discharge reactions, and that the input/output characteristics can be improved by reducing the difference in lattice area.
  • the lithium ion secondary battery may be simply referred to as the "battery”.
  • the charge and discharge reactions of LFP involve a change in the volume of the crystals, and this change in volume is affected by the size of the crystals. Therefore, as the crystals become larger, the stress that the volume change places on the crystals as particles increases, making the crystals more susceptible to structural defects such as cracks and fractures as a result of the charge and discharge reactions. For this reason, repeated charge and discharge reactions increase the number of crystals that cannot contribute to the charge and discharge reactions, resulting in a decline in cycle characteristics.
  • the difference in lattice area mentioned above is a change in the crystal structure itself, and does not have a large effect on the size of the crystal, but does affect the Li ion insertion/desorption reaction. Therefore, by controlling the difference in lattice area, it is possible to improve the input/output characteristics. Furthermore, the volume change of the crystal can also be reduced, which improves the cycle characteristics.
  • the rate of change in the lattice area of the b-axis-c-axis plane before and after full charge calculated from the lattice constants b and c of the positive electrode material i.e., the mismatch rate of the b-axis-c-axis plane
  • the mismatch rate is 1.10% or more and 1.33% or less.
  • the rate of change in the lattice area of the b-axis-c-axis plane of the positive electrode material before and after full charge is preferably 1.11% or more and 1.26% or less, more preferably 1.12% or more and 1.23% or less, and even more preferably 1.13% or more and 1.22% or less.
  • the mismatch rate can be calculated by the following formula (1), where s is the lattice area before charging and s' is the lattice area after full charging.
  • the lattice area can be calculated using a lattice constant calculated from a diffraction pattern measured by an X-ray diffraction device.
  • Inconsistency rate (%) (s - s') / s ⁇ 100 ...
  • the mismatch rate can be reduced by replacing Fe in the LFP with an element having a small difference between the divalent and trivalent ionic radii, an element having an intermediate ionic radius relative to Fe, etc.
  • inert elements such as Mg, which do not change in valence from divalent to trivalent, have a large effect of reducing the mismatch rate.
  • the amount of Mg added is set in the z range of the above composition to 0 ⁇ z ⁇ 0.1, so that it can be substituted for Fe and the mismatch rate in the bc plane can be reduced.
  • z is preferably set to 0.01 ⁇ z ⁇ 0.1, more preferably 0.03 ⁇ z ⁇ 0.1, and even more preferably 0.06 ⁇ z ⁇ 0.1.
  • the additive element A in the positive electrode material can be in the range of 1-y-z in the above composition, 0.2 ⁇ y+z ⁇ 1, i.e., 0 ⁇ 1-y-z ⁇ 0.8.
  • the additive element A can be added for the purpose of improving battery characteristics such as output characteristics and charge/discharge characteristics.
  • ⁇ can be preferably set to -0.05 ⁇ 0.03, more preferably -0.01 ⁇ 0.03.
  • the rate of change in lattice volume of the positive electrode material before and after full charge can be set to 4.90% to 6.06%.
  • the rate of change in lattice volume of the positive electrode material before and after full charge is preferably 4.95% or more and 6.00% or less, more preferably 5.00% or more and 5.60% or less, and even more preferably 5.00% or more and 5.30% or less.
  • the rate of change in lattice volume before and after full charge can be calculated by the following formula (2), where v is the lattice volume before charge and v' is the lattice area after full charge.
  • the lattice volume can be calculated using the lattice constant calculated from the diffraction pattern measured by an X-ray diffractometer.
  • Lattice volume change rate (%) [(v-v')/v] ⁇ 100 (2)
  • the positive electrode material of this embodiment can have a crystallite diameter of 80 nm or more and 150 nm or less. By setting the crystallite diameter within the above range, it is possible to improve the crystallinity and ensure sufficient battery characteristics such as charge/discharge characteristics and cycle characteristics.
  • the crystallite diameter can be determined from the peak of the X-ray diffraction pattern using Scherrer's formula. From the above viewpoint, the crystallite diameter is more preferably 110 nm or more and 134 nm or less, and even more preferably 110 nm or more and 133 nm or less.
  • the positive electrode material can have a specific surface area of 6.0 m 2 /g or more and 14.0 m 2 /g or less, which allows sufficient contact between the electrolyte and the positive electrode material, provides high charge/discharge characteristics, and suppresses the generation of fine particles to increase the packing density in the battery.
  • the specific surface area of the positive electrode material is preferably from 6.8 m 2 /g to 13.5 m 2 /g, more preferably from 8.0 m 2 /g to 13.0 m 2 /g, and even more preferably from 8.7 m 2 /g to 12.5 m 2 /g.
  • the positive electrode material can have a tap density of 1.1 g/cm 3 or more.
  • the tap density is an index of the packing density in the battery, and by making it 1.1 g/cm 3 or more, the charge/discharge capacity per unit volume can be sufficiently increased.
  • the upper limit of the tap density is not particularly limited, but can be, for example, 3.0 g/cm 3 or less.
  • the positive electrode material can have an NMP (N-methyl-2-pyrrolidone) absorption of 40 mL/100 g or less.
  • the NMP absorption is an index representing the amount of voids in the positive electrode material, and by setting the NMP absorption to 40 mL/100 g or less, the amount of voids can be restricted and the packing density in the battery can be increased.
  • the lower limit of the NMP absorption is not particularly limited, but can be set to 20 mL/100 g or more from the viewpoint of improving contact with the electrolyte.
  • the NMP absorption amount is preferably from 28 mL/100 g to 40 mL/100 g, more preferably from 30 mL/100 g to 39 mL/100 g, and even more preferably from 32 mL/100 g to 38 mL/100 g.
  • the NMP absorption amount can be measured in accordance with JIS K6217-4:2017 using NMP instead of DBP (dibutyl phthalate).
  • the positive electrode material can have a green density of 2.4 g/cm3 or more when compressed with a pressure of 16 kN. This allows a high-density positive electrode to be formed, and the charge/discharge capacity per unit volume of the battery can be sufficiently increased.
  • the green density is not particularly limited, but can be 3.0 g/ cm3 or less.
  • the green density is preferably 2.5 g/ cm3 or more.
  • the method for measuring the green density is not particularly limited, but for example, a certain amount of sample is placed in a mold with an inner diameter of 20 mm, and a load of 16 kN is applied.
  • the volume of the sample is calculated from the measured value of the sample height when the load is applied, and the green density can be obtained by dividing the mass of the sample by the volume.
  • the method for producing the positive electrode material for lithium ion secondary batteries of this embodiment is a method for producing the positive electrode material for lithium ion secondary batteries of this embodiment described above, and includes a crystallization step, a water washing step, a mixing step, and a firing step.
  • this production method the method for producing the positive electrode material for lithium ion secondary batteries of this embodiment may be simply referred to as "this production method.” Each step of the manufacturing method will be described below, but some parts that have already been described may be omitted.
  • crystallized particles are obtained by a crystallization reaction using a metal source having a valence of divalent, trivalent, or both, and a phosphate source.
  • the crystallized particles are usually metal phosphate complex compounds.
  • the amount of the phosphate source added is controlled so that the ratio of the amount of P to the total amount of iron (Fe), magnesium (Mg), and metal element (A) in the crystallized particles (P/(Fe+Mg+A)) is 0.95 to 1.03, preferably 0.96 to 1.02.
  • the raw material solution in which the metal source and phosphate source are dissolved and coexist as ions is added to an aqueous reaction solution adjusted to a pH range of 7 to 10 at a standard liquid temperature of 25°C, and co-precipitated. Since the raw material solution is acidic, an alkali is added dropwise to the aqueous reaction solution, and the raw material solution is added dropwise while maintaining the pH in the above range, thereby obtaining crystallized particles that are a coprecipitate.
  • the raw material solution in which the metal source and phosphate source are dissolved has a uniform composition, and by dropping this into a reaction aqueous solution whose pH is controlled to 7-10, preferably 7-9, at a liquid temperature of 25°C, the ratio of metal to phosphate is controlled, and crystallized particles of uniform composition can be obtained.
  • the composition of the precursor can be controlled by controlling the composition of the raw solution.
  • the ratio of the amount of P to the total of Fe, Mg, and metal element A (P/(Fe+Mg+A)) can be made the same as the composition of the desired precursor.
  • P/(Fe+Mg+A)) can be 0.95 to 1.03, or may be 0.96 to 1.02.
  • the metal source may be a water-soluble divalent or trivalent metal salt, preferably a sulfate.
  • a sulfate For example, iron sulfate, magnesium sulfate, zinc sulfate, cobalt sulfate, nickel sulfate, titanium sulfate, vanadium sulfate, etc. may be used as the metal source. Hydroxides soluble in acid may also be used.
  • the metal source may be used alone or in combination of two or more kinds, but it is preferable to use only one kind.
  • the phosphate source may be any water-soluble phosphate compound, and preferably includes orthophosphoric acid ( H3PO4 ) , ammonium dihydrogen phosphate ( NH4H2PO4 ), diammonium hydrogen phosphate (( NH4 ) 2HPO4 ) , etc. , which are less likely to be contaminated by impurities.
  • the phosphate source may be used alone or in combination of two or more kinds, but it is preferable to use only one kind.
  • an oxidizing agent such as an aqueous hydrogen peroxide (H 2 O 2 ) solution can be added to the reaction aqueous solution in order to adjust the valence of the metal source in the raw material solution.
  • the amount of the oxidizing agent to be added is not particularly limited, but can be in the range of 0.3 to 3.0 times the amount of the metal source substance.
  • the oxidizing agent may be used alone or in combination of two or more kinds.
  • alkali sources selected from the group consisting of sodium hydroxide and lithium hydroxide can be used.
  • the alkali source may be used alone or in combination of two or more kinds.
  • a complexing agent may be added to the reaction aqueous solution together with the alkali source.
  • the complexing agent is not particularly limited, and may be any agent capable of forming a complex by bonding with iron ions, other metal ions, etc. in the aqueous solution, such as an ammonium ion donor.
  • the complexing agent may be used alone or in combination of two or more kinds.
  • the ammonium ion donor is not particularly limited, but for example, ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.
  • the ammonium ion concentration in the reaction aqueous solution can be in the range of 3 g/L to 25 g/L.
  • the ammonium ion donor may be used alone or in combination of two or more kinds.
  • the alkali source and complexing agent can also be mixed and added to the reaction solution as a buffer solution.
  • a Mg source is added to the reaction aqueous solution.
  • the added Mg source is not only dissolved in the crystallized particles, but is also present on either or both of the surfaces and grain boundaries of the primary particles, allowing the composition ratio to be accurately controlled.
  • the Mg source may be added as an aqueous solution to the aqueous reaction solution individually or to the raw material solution.
  • magnesium sulfate, magnesium hydroxide, etc. can be used as the Mg source.
  • the phosphate source or metal source contains Mg as an impurity
  • the Mg contained in the phosphate source or metal source may be used.
  • the Mg source is not limited by the method of addition, and can be in a desired amount, for example, 0 ⁇ z ⁇ 0.1, which is the z range of the above composition that indicates the amount of Mg added in the desired LFP.
  • the Mg source may be used alone or in combination of two or more.
  • the crystallized particles obtained in the crystallization step are washed with water and dried to obtain the precursor of the positive electrode active material.
  • the precursor of the positive electrode active material may be simply referred to as the "precursor”.
  • Washing with water can be carried out by any conventional method as long as it reduces impurities.
  • the crystallized particles can be mixed with pure water, distilled water, or ion-exchanged water, which are free of impurities, and stirred, and then the crystallized particles can be washed with water after solid-liquid separation.
  • the crystallized particles can be dried in a non-oxidizing atmosphere such as a vacuum atmosphere or an inert gas atmosphere.
  • composition ratio of the metal element and phosphoric acid in the precursor obtained in the water washing step is inherited by the composition of the target positive electrode active material, so that the mixing ratio of the metal source and the phosphoric acid source used in the crystallization step can be determined so as to obtain the target composition.
  • ⁇ is preferably -0.05 ⁇ 0.03, and more preferably -0.04 ⁇ 0.02.
  • the precursor can also be expressed as, for example, the general formula Fe y Mg z A 1-y-z (PO 4 ) 1+ ⁇ .
  • the general formula is shown as the composition of the entire precursor, including magnesium phosphate (Mg 3 (PO 4 ) 2 ) particles present on the surface, grain boundaries, or both of the primary particles of the crystallized particles. That is, Mg is present in the form of (Mg 3 (PO 4 ) 2 ) particles on the surface of the primary particles of the precursor, on the grain boundaries between the primary particles, or on both the surface and the grain boundaries, and a part of it may be dissolved in the precursor. Since y, z, ⁇ , and the element M in the formula have already been explained, explanation will be omitted here.
  • the precursor may have a specific surface area of 7.0 m 2 /g or more and 12.0 m 2 /g or less. This enhances the reactivity between the lithium source and the precursor during firing, and further suppresses excessive sintering of the primary particles of the LFP.
  • the specific surface area of the precursor is preferably 8.8 m 2 /g or more and 11.5 m 2 /g or less, and more preferably 9.5 m 2 /g or more and 11.0 m 2 /g or less.
  • the precursor can have a particle size (D50) at a cumulative percentage of 50% in the cumulative particle size distribution of 0.5 ⁇ m or more and 5.0 ⁇ m or less.
  • the D50 of the precursor is preferably 1.9 ⁇ m or more and 5.0 ⁇ m or less, and more preferably 2.5 ⁇ m or more and 4.5 ⁇ m or less.
  • the specific surface area and D50 of the precursor can be controlled by the crystallization conditions, and by adjusting the pH, stirring conditions, etc., a precursor having a specific surface area and D50 within the above range can be obtained.
  • the mixing step the precursor of the positive electrode active material obtained in the water washing step, a lithium source, and a carbon source are mixed to obtain a raw material mixture. If necessary, a phosphorus source may be further mixed.
  • the precursor and the lithium source are mixed so that the ratio of the amount of substance of lithium (Li) to the amount of substance of metal other than lithium (Me) in the resulting LFP, x (Li/Me), is preferably more than 0.9 and less than 1.1, more preferably 0.95 or more and 1.05 or less.
  • the ratio of the amount of substance of metal to phosphorus in the precursor (P/(Fe+Mg+A)) is less than 1, it is preferable to mix a phosphorus source and set the ratio of metal to phosphorus to 0.99 or more and 1.03 or less.
  • P/(Fe+Mg+A) of the positive electrode material By setting the P/(Fe+Mg+A) of the positive electrode material to 0.99 or more, it is possible to suppress the elution of metal elements that are not dissolved in the crystal of the olivine structure due to the charge/discharge reaction, and to further improve the durability and safety of the lithium ion secondary battery. Therefore, it is preferable to set P/(Fe+Mg+A) to 0.99 or more and 1.03 or less in the mixing process.
  • the x in the raw material mixture subjected to the firing process will be almost the same as the Li/Me in the resulting LFP. For this reason, in the mixing process, it is preferable to mix so that the resulting LFP has the desired x.
  • x may decrease slightly due to the volatilization of lithium, etc. Therefore, it is preferable to make x in the mixing process higher than x in the desired LFP by the amount of decrease in x.
  • the decrease in x is almost constant depending on the sintering conditions, so it can be easily determined by preliminary tests, etc.
  • the lithium source is not particularly limited, and lithium carbonate, lithium hydroxide, lithium sulfate, etc. can be used. Lithium carbonate and lithium hydroxide that are free of impurities can be preferably used.
  • the lithium source may be used alone or in combination of two or more kinds, but it is preferable to use only one kind.
  • carbon sources examples include graphite such as natural graphite and artificial graphite, carbon blacks such as acetylene black and ketjen black, carbon fiber, sucrose, ascorbic acid, and other organic compounds that produce carbonaceous matter upon decomposition, and these can be used alone or in combination of two or more kinds.
  • the carbon source may be used alone or in combination of two or more kinds.
  • the amount of carbon source to be mixed is not particularly limited, as long as the LFP is coated with a conductive carbonaceous film, and 1 to 5 mass % of carbon can be mixed with the LFP.
  • the phosphorus source is not particularly limited, and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ), diammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 ), etc. can be used.
  • the phosphorus source may be used alone or in combination of two or more kinds.
  • a general mixer can be used as a mixing means for mixing the precursor and the lithium compound, such as a shaker mixer, a Loedige mixer, a Julia mixer, or a V blender.
  • the firing step the raw material mixture obtained in the mixing step is fired in a non-oxidizing atmosphere to obtain a positive electrode material containing a positive electrode active material.
  • the firing temperature at which the raw material mixture is fired i.e., the maximum temperature set in the firing furnace, is not particularly limited, but is preferably, for example, 600°C to 850°C, and more preferably 600°C to 750°C.
  • the calcination temperature 600°C or higher, it is possible to sufficiently advance the diffusion of lithium into the precursor, making the crystal structure of the resulting LFP particularly uniform, and sufficiently improving the battery characteristics when used as a positive electrode active material.
  • the reaction between the lithium source and the precursor can be sufficiently advanced, it is possible to further suppress the remaining of excess lithium or unreacted precursor particles.
  • magnesium phosphate particles are present on either or both of the surface and grain boundaries of the primary particles of the precursor.
  • the magnesium phosphate particles diffuse into the precursor together with Li in the lithium source, forming an LFP with an olivine structure in which part of the iron is replaced with magnesium, and the inconsistency is reduced as described above.
  • the above-mentioned phosphate compound is used as the precursor, and the precursor is mixed with a lithium source and fired in a state in which fine magnesium phosphate particles are present on either or both of the surface and grain boundaries of the primary particles of the precursor. Therefore, compared to a manufacturing method in which an iron source, a magnesium source, etc. are mixed with a phosphate source and a lithium source as separate raw materials and fired, magnesium and added elements are more uniformly dispersed in the crystals of the LFP, and the effect of reducing the inconsistency is considered to be greater.
  • the holding time at the firing temperature is not particularly limited, but can be the general conditions for firing LFP, for example, 0.5 to 12 hours, preferably 2 to 6 hours.
  • the atmosphere during firing may be a non-oxidizing atmosphere, but is not particularly limited; for example, it may be an inert atmosphere such as nitrogen, or a reducing atmosphere.
  • the atmosphere during firing is an atmosphere excluding gases generated by the reaction during firing, and can be, for example, the atmospheric gas supplied to the firing furnace.
  • the calcination can be performed at a calcination temperature lower than the firing temperature, for example, 350°C to 550°C, preferably 400°C to 500°C.
  • the holding time at the calcination temperature can be, for example, 0.5 to 12 hours, preferably 2 to 6 hours.
  • the mixture After the calcination, the mixture can be cooled and then calcined. Alternatively, the mixture can be heated from the calcination temperature to the calcination temperature and then calcined.
  • the atmosphere in which the pre-firing is carried out is not particularly limited, but may be, for example, the same atmosphere as that in the firing step.
  • the firing furnace is not particularly limited, and may be any furnace capable of firing the raw material mixture in an inert or reducing atmosphere. From the viewpoint of maintaining a uniform atmosphere inside the furnace, an electric furnace that does not generate gas is preferable, and either a batch or continuous furnace may be used. In addition, either a furnace in which the raw material mixture is filled into a firing container and fired, or a furnace in which the mixture is flowed and fired, may be used. However, from the viewpoint of particularly increasing productivity, it is preferable to use a continuous firing furnace in the firing process.
  • the powder of the positive electrode material obtained by the firing step may be aggregated or slightly sintered.
  • the present production method may optionally include a crushing step of crushing the powder after the firing step.
  • crushing refers to the operation of applying mechanical energy to an agglomerate consisting of multiple secondary particles that is formed by sintering necking between secondary particles during firing, separating the secondary particles with almost no destruction of the secondary particles themselves, and breaking up the agglomerates.
  • composition of the positive electrode material The composition of the positive electrode material produced by the above-described production method is not particularly limited.
  • the positive electrode material is a positive electrode material including a positive electrode active material composed of aggregate particles in which a plurality of primary particles coated with a carbonaceous film are aggregated,
  • the metal element A may be at least one additive element selected from the group consisting of Zn, Co, Ni, Ti, and V.
  • x may be 0.95 ⁇ x ⁇ 1.05.
  • phosphoric acid (PO 4 ) can be contained in the above substance amount ratio at a ratio of 1+ ⁇ , where ⁇ satisfies ⁇ 0.05 ⁇ 0.03, preferably ⁇ 0.01 ⁇ 0.03.
  • the positive electrode active material can also be expressed by the general formula LixFeyMgzA1 - yz ( PO4 ) 1+ ⁇ , for example.Since x, y, ⁇ , and the element A in the formula have already been explained, explanation thereof will be omitted here.
  • the manufacturing method described above can provide a positive electrode material containing lithium iron phosphate that has high input/output characteristics when used as a positive electrode for a lithium-ion secondary battery.
  • the positive electrode for a lithium ion secondary battery of this embodiment is a positive electrode for a lithium ion secondary battery including an aluminum current collector and a positive electrode mixture layer formed on the aluminum current collector,
  • the positive electrode mixture layer contains the above-described positive electrode material for a lithium ion secondary battery according to this embodiment.
  • the positive electrode is a sheet-like member, and is formed, for example, by applying a positive electrode composite paste containing the above-mentioned positive electrode material as a positive electrode active material onto the surface of an aluminum foil current collector (aluminum current collector) and drying it.
  • the positive electrode is appropriately processed according to the battery to be used, for example, by cutting to a size appropriate for the target secondary battery, or by compressing with a roll press or the like to increase the electrode density.
  • the positive electrode mixture paste is formed by adding a solvent to the positive electrode mixture and kneading it.
  • the positive electrode mixture is formed by mixing the powdered positive electrode material described above with a conductive material and a binder.
  • the conductive material is added to the electrode to provide it with suitable electrical conductivity.
  • the conductive material is not particularly limited, but examples thereof include graphite (natural graphite, artificial graphite, expanded graphite, etc.); acetylene black, Ketjen Black (registered trademark), and other carbon black-based materials.
  • the conductive material may be used alone or in combination of two or more kinds.
  • the binder plays a role of binding the positive electrode active material particles.
  • the binder used in this positive electrode mixture is not particularly limited, but for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulose-based resin, polyacrylic acid, etc. can be used.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • fluororubber fluororubber
  • ethylene propylene diene rubber ethylene propylene diene rubber
  • styrene butadiene cellulose-based resin
  • polyacrylic acid etc.
  • the binder may be used alone or in combination of two or more kinds.
  • activated carbon or the like may be added to the positive electrode mixture.
  • activated carbon or the like By adding activated carbon or the like to the positive electrode mixture, the electric double layer capacity of the positive electrode can be increased.
  • the solvent dissolves the binder and disperses the positive electrode active material, the conductive material, the activated carbon, etc. in the binder.
  • This solvent is not particularly limited, but for example, an organic solvent such as N-methyl-2-pyrrolidone can be used.
  • the solvent may be used alone or in combination of two or more kinds.
  • the mixing ratio of each substance in the positive electrode mixture paste there are no particular limitations on the mixing ratio of each substance in the positive electrode mixture paste.
  • the content of the positive electrode active material can be 60 parts by mass to 98 parts by mass
  • the content of the conductive material can be 1 part by mass to 20 parts by mass
  • the content of the binder can be 1 part by mass to 20 parts by mass, similar to the positive electrodes of general lithium-ion secondary batteries.
  • the positive electrode may contain the positive electrode material of this embodiment.
  • the battery of the present embodiment has a structure substantially similar to that of a general lithium ion secondary battery, except that a positive electrode material obtained by the above-described method for producing a positive electrode material for a lithium ion secondary battery is used as the positive electrode material, more specifically, as the positive electrode active material.
  • the battery of this embodiment has a structure including a case, a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, which are contained within the case. More specifically, if a non-aqueous electrolyte is used, for example, the positive electrode and the negative electrode are laminated with a separator interposed therebetween to form an electrode body, the resulting electrode body is impregnated with a non-aqueous electrolyte, and the positive electrode current collector of the positive electrode and the positive electrode terminal connected to the outside, and the negative electrode current collector of the negative electrode and the negative electrode terminal connected to the outside are connected using current collecting leads or the like, and the secondary battery of this embodiment is formed by sealing the case.
  • a non-aqueous electrolyte for example, the positive electrode and the negative electrode are laminated with a separator interposed therebetween to form an electrode body, the resulting electrode body is impregnated with a non-aqueous electrolyte, and the positive electrode current collector of the
  • the structure of the secondary battery of this embodiment is not limited to the above example, and the external shape can be various shapes such as a cylindrical shape or a laminated shape.
  • the positive electrode has already been described, so a description thereof will be omitted.
  • the negative electrode is a sheet-like member formed by applying a negative electrode composite paste to the surface of a metal foil current collector such as copper, and then drying it.
  • a negative electrode composite paste to the surface of a metal foil current collector such as copper, and then drying it.
  • the components constituting the negative electrode composite paste and their blending, the material of the current collector, and the like, of this negative electrode are different, they are formed in substantially the same manner as the positive electrode, and are subjected to various treatments as necessary, in the same manner as the positive electrode.
  • the negative electrode mixture paste is made by adding an appropriate solvent to the negative electrode mixture, which is a mixture of the negative electrode active material and binder, to form a paste.
  • the negative electrode active material can be, for example, a material containing lithium, such as metallic lithium or a lithium alloy, or an occlusion material capable of occluding and desorbing lithium ions.
  • the storage material is not particularly limited, but examples include natural graphite, artificial graphite, sintered organic compounds such as phenolic resin, and powdered carbon materials such as coke.
  • a fluorine-containing resin such as PVDF can be used as the binder, just like the positive electrode, and an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent for dispersing the negative electrode active material in the binder.
  • the separator is sandwiched between the positive electrode and the negative electrode when a non-aqueous electrolyte is used, and has the function of separating the positive electrode and the negative electrode and retaining the electrolyte.
  • the separator may be, for example, a thin membrane such as polyethylene or polypropylene having a large number of fine pores, but is not particularly limited as long as it has the above function.
  • Non-aqueous electrolyte As the non-aqueous electrolyte, for example, a non-aqueous electrolytic solution can be used. As the non-aqueous electrolyte, for example, a solution in which a lithium salt as a supporting salt is dissolved in an organic solvent can be used. Alternatively, as the non-aqueous electrolyte, a solution in which a lithium salt is dissolved in an ionic liquid can be used. Note that the ionic liquid refers to a salt that is composed of cations and anions other than lithium ions and is liquid even at room temperature (25°C).
  • organic solvent examples include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran, and dimethoxyethane; sulfur compounds such as ethyl methyl sulfone and butane sultone; and phosphorus compounds such as triethyl phosphate and trioctyl phosphate.
  • the organic solvent may be one selected from the above-mentioned compound group, or two or more of them may be mixed and used.
  • the supporting salt may be LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN(CF 3 SO 2 ) 2 , or a composite salt thereof.
  • the non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, and the like.
  • the supporting salt may be used alone or in combination of two or more kinds.
  • a solid electrolyte may be used as the non-aqueous electrolyte.
  • a solid electrolyte has the property of being able to withstand high voltages.
  • Examples of solid electrolytes include inorganic solid electrolytes and organic solid electrolytes.
  • Inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes.
  • oxide-based solid electrolyte is not particularly limited, and for example, one that contains oxygen (O) and has lithium ion conductivity and electronic insulation properties can be suitably used.
  • oxide-based solid electrolytes include lithium phosphate (Li 3 PO 4 ), Li 3 PO 4 N x , LiBO 2 N x , LiNbO 3 , LiTaO 3 , Li 2 SiO 3 , Li 4 SiO 4 -Li 3 PO 4 , Li 4 SiO 4 -Li 3 VO 4 , Li 2 O-B 2 O 3 -P 2 O 5 , Li 2 O-SiO 2 , Li 2 O-B 2 O 3 -ZnO, Li 1+X Al X Ti 2-X (PO 4 ) 3 (0 ⁇ X ⁇ 1), Li 1+X Al X Ge 2-X (PO 4 ) 3 (0 ⁇ X ⁇ 1 ) , LiTi2 ( PO4 ) 3 , Li3XLa2 /3-XTiO3 ( 0 ⁇ X ⁇
  • the sulfide-based solid electrolyte is not particularly limited, and for example, one containing sulfur (S) and having lithium ion conductivity and electronic insulation can be suitably used.
  • examples of the sulfide-based solid electrolyte include Li 2 S-P 2 S 5 , Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 S-P 2 S 5 , LiI-Li 2 S-B 2 S 3 , Li 3 PO 4 -Li 2 S-Si 2 S, Li 3 PO 4 -Li 2 S-SiS 2 , LiPO 4 -Li 2 S-SiS, LiI-Li 2 S-P 2 O 5 , LiI-Li 3 PO 4 -P 2 S 5 and the like.
  • the sulfide-based solid electrolyte may be one or more selected from these.
  • inorganic solid electrolyte materials other than those mentioned above may be used, for example, Li 3 N, LiI, Li 3 N-LiI-LiOH, etc. may be used.
  • the organic solid electrolyte is not particularly limited as long as it is a polymer compound exhibiting ion conductivity, and examples of the organic solid electrolyte that can be used include polyethylene oxide, polypropylene oxide, copolymers thereof, etc.
  • the organic solid electrolyte may also contain a supporting salt (lithium salt).
  • the organic solid electrolyte may be used alone or in combination of two or more.
  • the battery of this embodiment can be made into various shapes such as a cylindrical shape or a laminated shape. Regardless of the shape, when the secondary battery of this embodiment uses a non-aqueous electrolyte solution as the non-aqueous electrolyte, the positive electrode and the negative electrode are laminated via a separator to form an electrode body. The obtained electrode body is impregnated with a non-aqueous electrolyte solution, and the positive electrode current collector and the positive electrode terminal connected to the outside, and the negative electrode current collector and the negative electrode terminal connected to the outside are connected using a current collecting lead or the like, and the structure can be sealed in a battery case.
  • the battery according to this embodiment is not limited to a form using a non-aqueous electrolytic solution as the non-aqueous electrolyte, but can also be, for example, a secondary battery using a solid non-aqueous electrolyte, i.e., an all-solid-state battery.
  • an all-solid-state battery the configuration other than the positive electrode material can be appropriately changed as necessary.
  • the battery according to this embodiment has excellent battery capacity and input/output characteristics because it uses the positive electrode material according to this embodiment as the positive electrode material. Therefore, the battery according to this embodiment can be suitably used as a chargeable/dischargeable battery in mobile phones, smartphones, tablets, notebook computers and other portable information terminals, portable music players, digital cameras, medical equipment, clean energy automobiles such as HEVs (Hybrid Electric Vehicles), EVs (Electric Vehicles), and PHEVs (Plug-in Hybrid Electric Vehicles), etc.
  • HEVs Hybrid Electric Vehicles
  • EVs Electric Vehicles
  • PHEVs Plug-in Hybrid Electric Vehicles
  • composition analysis The composition of the positive electrode active material precursor and the positive electrode material was measured using ICP emission spectrometry.
  • Lattice area and lattice volume of the bc plane of the positive electrode material A composite layer of an active material was peeled off from a positive electrode for a lithium ion secondary battery (evaluation battery) produced by the method described below, and the crystal lattice constant and the lattice volume before charging were calculated from the diffraction pattern of the composite layer measured using an X-ray diffractometer. Further, the evaluation battery prepared by the method described later was fully charged at room temperature (25° C.) with a constant current of 0.1 C and an upper limit voltage of 3.7 V, and then the evaluation battery was disassembled and the positive electrode was removed.
  • a lithium ion secondary battery evaluation battery
  • the removed positive electrode was thoroughly washed with diethyl carbonate (DEC), dried at room temperature under reduced pressure for 12 hours, and then vacuum dried at 50° C. for 12 hours.
  • DEC diethyl carbonate
  • the active material composite layer was peeled off from the dried positive electrode, and the crystal lattice constant after charging was determined from the diffraction pattern of the composite layer measured using an X-ray diffractometer, and the lattice area and lattice volume were calculated.
  • Crystallite diameter of the positive electrode material was measured using an X-ray diffractometer under the following measurement conditions. Radiation source: Cu-K ⁇ Step size: 0.01°/step Scan speed: 3 seconds/step In the measured diffraction pattern, the half-width (B) of the peak in the 2 ⁇ range of 28.8 to 30.8° was used to calculate the crystallite size from the following formulas (i) and (ii).
  • B is the half-width of the peak in the 2 ⁇ range of 28.8 to 30.8° in the diffraction pattern measured for the positive electrode active material particles
  • Specific surface area The specific surface areas of the precursor and the positive electrode material were determined by the BET single-point method using nitrogen gas adsorption.
  • Average particle size of the precursor The particle size at cumulative percentage 50% (D50) on a volume basis was determined using a laser diffraction scattering particle size distribution measuring device.
  • Tap density The tap density of the positive electrode material was measured by shaking the sample container containing the positive electrode material 500 times using a tapping machine (KRS-409, manufactured by Kuramochi Scientific Instruments Manufacturing Co., Ltd.).
  • NMP absorption amount of positive electrode material Measured using NMP in accordance with JIS K 6217-4:2017.
  • a laminated secondary battery 10 (see FIG. 1) was manufactured as a lithium ion secondary battery for evaluation, and the battery characteristics (load characteristics, DC resistance, and cycle characteristics) were evaluated.
  • the laminated secondary battery 10 was manufactured and the battery characteristics were evaluated as follows.
  • PVdF polyvinylidene fluoride
  • AB acetylene black
  • NMP N-methyl-2-pyrrolidone
  • the slurry was then applied onto an aluminum (Al) foil (current collector) having a thickness of 30 ⁇ m and vacuum dried at 120° C. for 12 hours. After that, the coating was cut into strips having a width of 35 mm and pressed twice with a roll press at a roll gap of 5 ⁇ m and a roll feed rate of 0.5 m/min to produce the positive electrodes 11 of the examples and comparative examples.
  • a laminate type secondary battery (battery for evaluation) 10 has a structure in which a laminate of a positive electrode 11, a separator 12, and a negative electrode 13 is impregnated with an electrolyte solution and sealed with a laminate (aluminum laminate film) 14.
  • a positive electrode tab 15 is connected to the positive electrode 11, and a negative electrode tab 16 is connected to the negative electrode 13, and the positive electrode tab 15 and the negative electrode tab 16 are exposed to the outside of the laminate 14.
  • a negative electrode 13 was prepared by applying a negative electrode mixture paste, which is a mixture of natural graphite powder with an average particle size of about 20 ⁇ m and polyvinylidene fluoride, to copper foil.
  • the resulting positive electrode 11 and negative electrode 13 were cut to a specified size, and a positive electrode tab 15 was welded to the positive electrode 11, and a negative electrode tab 16 was welded to the negative electrode 13.
  • the positive electrode 11 and negative electrode 13 were placed in a laminate 14 via a separator 12 made of a porous polypropylene film.
  • LiPF 6 was added and dissolved in the mixed solution to a concentration of 1 mol/dm 3
  • VC vinylene carbonate
  • the obtained electrolyte solution was injected into the laminate 14 and sealed to prepare a laminate type secondary battery 10.
  • the obtained laminate type secondary battery 10 was evaluated by the following method.
  • a charge and discharge test of the laminated secondary battery was performed at room temperature (25° C.) by repeatedly charging and discharging three times at a constant current of 0.1 C and a cutoff voltage of 2.5 V to 3.7 V.
  • the lithium ion secondary battery was charged and discharged at a constant current of 0.1 C and a cutoff voltage of 2.5 V to 3.7 V at an environmental temperature of 0° C., and the discharge capacity was measured.
  • the battery was charged at 0.1 C and a cutoff voltage of 2.5 V to 3.7 V at an environmental temperature of 0° C., and discharged at 3 C, and the discharge capacity was measured.
  • Load characteristic (%) (3C discharge capacity/0.1C discharge capacity) x 100 (A)
  • Cycle characteristics (capacity retention rate)
  • the battery was repeatedly charged and discharged 300 times at an environmental temperature of 60° C., a cutoff voltage of 2.5 V to 3.7 V, and a constant current of a charge/discharge rate of 1 C.
  • Example 1 (Preparation of Positive Electrode Active Material Precursor) 279 g of FeSO 4 ⁇ 7H 2 O was dissolved in pure water as an Fe source. 130 g of H 3 PO 4 (75 mass% aqueous solution) and 3.08 g of Mg (OH) 2 were mixed and dissolved in the resulting solution as a P source. Next, 170 g of H 2 O 2 (30 W / V% aqueous solution) as an oxidizing agent and pure water for concentration adjustment were added to the mixed aqueous solution to prepare a raw material solution. In addition, sodium hydroxide (30 mass% aqueous solution) and ammonia water (28 mass% aqueous solution) were mixed in a molar ratio of 1:1 to prepare a buffer solution.
  • reaction solution was filtered and dehydrated and washed several times with distilled water to obtain cake-like crystallized particles, which were then vacuum-dried at 50° C. for 24 hours to obtain a precursor of the positive electrode active material (FePO 4 ).
  • the obtained precursor was observed with a scanning electron microscope, it was confirmed that it was composed of secondary particles formed by aggregation of primary particles of FePO4 , and that fine Mg3 ( PO4 ) 2 particles of 10 nm to 300 nm were present on the particle surfaces of the primary particles.
  • the ratio of the amount of P to the total amount of Fe, Mg, and the metal element A (P/(Fe+Mg+A)) was 0.98.
  • the specific surface area was 9.7 m 2 /g, and D50 was 2.3 ⁇ m.
  • the evaluation results of the obtained precursor are shown in Table 1.
  • LiOH lithium hydroxide
  • NH 4 H 2 PO 4 ammonium dihydrogen phosphate
  • the obtained raw material mixture was heat-treated in a nitrogen atmosphere at 700°C for 5 hours to synthesize the positive electrode active material and to support carbon on the particle surface of the positive electrode active material, thereby producing the positive electrode material for lithium-ion secondary batteries of Example 1.
  • the positive electrode active material was composed of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the obtained positive electrode material and the lithium ion secondary battery using the positive electrode material are summarized in Table 2.
  • Example 2 A positive electrode material for a lithium ion secondary battery of Example 2 was prepared and evaluated in the same manner as in Example 1, except that 6.12 g of Mg(OH) 2 and 129 g of H3PO4 (75% aqueous solution) were mixed when preparing the precursor of the positive electrode active material.
  • the obtained precursor was observed with a scanning electron microscope, it was confirmed that it was composed of secondary particles formed by aggregation of primary particles of FePO4 , and that fine Mg3 ( PO4 ) 2 particles of 10 nm to 300 nm were present on the particle surfaces of the primary particles.
  • the ratio of the amount of P to the total amount of Fe, Mg, and the metal element A was 0.96.
  • the specific surface area was 10.6 m 2 /g, and D50 was 4.1 ⁇ m.
  • the evaluation results of the obtained precursor are shown in Table 1.
  • the positive electrode active material was composed of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the obtained precursor are shown in Table 1, and the evaluation results of the obtained positive electrode material and the lithium ion secondary battery using the positive electrode material are shown in Table 2.
  • Example 3 A positive electrode material for a lithium ion secondary battery of Example 3 was prepared and evaluated in the same manner as in Example 1, except that the amount of Mg(OH) 2 mixed when preparing the precursor of the positive electrode active material was 1.19 g.
  • the obtained precursor was observed with a scanning electron microscope, it was confirmed that it was composed of secondary particles formed by aggregation of primary particles of FePO4 , and that fine Mg3 ( PO4 ) 2 particles of 10 nm to 300 nm were present on the particle surfaces of the primary particles.
  • the ratio of the amount of P to the total amount of Fe, Mg, and the metal element A was 0.99.
  • the specific surface area was 8.4 m 2 /g, and D50 was 1.2 ⁇ m.
  • the evaluation results of the obtained precursor are shown in Table 1.
  • the positive electrode active material was composed of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the obtained positive electrode material and the lithium ion secondary battery using the positive electrode material are summarized in Table 2.
  • LiOH lithium hydroxide
  • the positive electrode active material was composed of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the precursor are summarized in Table 1, and the evaluation results of the obtained positive electrode material and the lithium-ion secondary battery using the positive electrode material are summarized in Table 2.
  • LiOH lithium hydroxide
  • the positive electrode active material was composed of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the precursor are shown in Table 1, and the evaluation results of the obtained positive electrode material and the lithium-ion secondary battery using the positive electrode material are shown in Table 1.
  • Comparative Example 1 A positive electrode material for a lithium ion secondary battery of Comparative Example 1 was prepared and evaluated in the same manner as in Example 1, except that, when preparing the precursor of the positive electrode active material, Mg(OH) 2 was not mixed, but 131 g of H3PO4 (75% aqueous solution) was mixed, and, when mixing the precursor and the Li source, ammonium dihydrogen phosphate was not mixed.
  • the obtained precursor was observed with a scanning electron microscope, it was confirmed that it was composed of secondary particles formed by aggregation of primary particles of FePO4 .
  • the ratio of the amount of P to the total amount of Fe, Mg, and the metal element A was 1.04.
  • the specific surface area was 10.4 m 2 /g, and D50 was 1.8 ⁇ m.
  • the evaluation results of the obtained precursor are shown in Table 1.
  • the resulting positive electrode material confirmed that LFP was produced as the positive electrode active material. Furthermore, when the resulting positive electrode material was observed with a scanning electron microscope, it was found to be composed of a positive electrode active material made up of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the obtained precursor are shown in Table 1, and the evaluation results of the obtained positive electrode material and the lithium ion secondary battery using the positive electrode material are shown in Table 2.
  • Comparative Example 2 A positive electrode material for a lithium ion secondary battery of Comparative Example 2 was prepared and evaluated in the same manner as in Example 1, except that 8.36 g of Mg(OH) 2 and 128 g of H3PO4 (75% aqueous solution) were mixed when preparing the precursor of the positive electrode active material.
  • the obtained precursor was observed with a scanning electron microscope, it was confirmed that it was composed of secondary particles formed by aggregation of primary particles of FePO4 , and that fine Mg3 ( PO4 ) 2 particles of 10 nm to 300 nm were present on the particle surfaces of the primary particles.
  • the ratio of the amount of P to the total amount of Fe, Mg, and metal element A was 0.94.
  • the specific surface area was 8.7 m 2 /g, and D50 was 2.7 ⁇ m.
  • the evaluation results of the obtained precursor are shown in Table 1.
  • the positive electrode active material was composed of secondary particles formed by the aggregation of primary particles of LFP.
  • the evaluation results of the obtained precursor are shown in Table 1, and the evaluation results of the obtained positive electrode material and the lithium ion secondary battery using the positive electrode material are shown in Table 2.
  • Examples 1 to 5 are superior in load characteristics, DC resistance, and cycle characteristics to Comparative Examples 1 and 2.
  • Comparative Example 1 is not substituted with Mg, and therefore the lattice distortion and volume change associated with the Li ion insertion/deinsertion reaction are large, which is believed to have deteriorated the load characteristics and input/output characteristics.
  • Comparative Example 2 has an excessive amount of Mg substitution, which is believed to have increased the reaction resistances and deteriorated the load characteristics and input/output characteristics.
  • the positive electrode material and manufacturing method of the present embodiment can provide a positive electrode material containing lithium iron phosphate that has excellent input/output characteristics and cycle characteristics when used as a positive electrode of a lithium ion secondary battery.

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PCT/JP2023/025770 2022-09-30 2023-07-12 リチウムイオン二次電池用正極材料及びその製造方法、リチウムイオン二次電池用正極、ならびにリチウムイオン二次電池 Ceased WO2024070137A1 (ja)

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CN118738337A (zh) * 2024-07-03 2024-10-01 蜂巢能源科技(上饶)有限公司 一种硅碳包覆磷酸亚铁锂正极材料及其制备方法、正极片、锂离子电池和用电设备

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JP2013518372A (ja) * 2010-01-28 2013-05-20 フォステック リチウム インコーポレイテッド カソード材料の最適化方法および強化された電気化学的特性を備えるカソード材料
CN108448070A (zh) * 2018-01-23 2018-08-24 四川大学 金属掺杂磷酸铁锂/碳复合材料及制备方法

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JP2013518372A (ja) * 2010-01-28 2013-05-20 フォステック リチウム インコーポレイテッド カソード材料の最適化方法および強化された電気化学的特性を備えるカソード材料
CN108448070A (zh) * 2018-01-23 2018-08-24 四川大学 金属掺杂磷酸铁锂/碳复合材料及制备方法

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* Cited by examiner, † Cited by third party
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CN118738337A (zh) * 2024-07-03 2024-10-01 蜂巢能源科技(上饶)有限公司 一种硅碳包覆磷酸亚铁锂正极材料及其制备方法、正极片、锂离子电池和用电设备
WO2026007934A1 (zh) * 2024-07-03 2026-01-08 蜂巢能源科技股份有限公司 一种硅碳包覆磷酸亚铁锂正极材料及其制备方法、正极片、锂离子电池和用电设备

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