WO2024157907A1 - 非水電解質二次電池用正極活物質および非水電解質二次電池 - Google Patents

非水電解質二次電池用正極活物質および非水電解質二次電池 Download PDF

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WO2024157907A1
WO2024157907A1 PCT/JP2024/001565 JP2024001565W WO2024157907A1 WO 2024157907 A1 WO2024157907 A1 WO 2024157907A1 JP 2024001565 W JP2024001565 W JP 2024001565W WO 2024157907 A1 WO2024157907 A1 WO 2024157907A1
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positive electrode
active material
electrode active
electrolyte secondary
aqueous electrolyte
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French (fr)
Japanese (ja)
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一成 池内
光宏 日比野
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Panasonic Energy Co Ltd
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Panasonic Energy Co Ltd
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Priority to JP2024573027A priority Critical patent/JPWO2024157907A1/ja
Priority to CN202480007353.6A priority patent/CN120500752A/zh
Priority to EP24747235.0A priority patent/EP4657568A1/en
Publication of WO2024157907A1 publication Critical patent/WO2024157907A1/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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C01G53/502—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt
    • C01G53/504—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • 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
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/45—Aggregated particles or particles with an intergrown morphology
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • 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
    • C01P2004/61—Micrometer sized, i.e. from 1-100 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
    • C01P2006/12—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

  • This disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery using the positive electrode active material.
  • the positive electrode active material has a significant effect on battery performance such as input/output characteristics, capacity, and durability, and therefore has been the subject of much research.
  • lithium transition metal composite oxides containing transition metal elements such as Ni and Mn are used as positive electrode active materials.
  • the type and amount of elements contained in the lithium transition metal composite oxide, as well as the crystal structure of the composite oxide, have a significant effect on battery performance, and even slight changes in these physical properties may make it impossible to achieve the desired performance.
  • Patent Documents 1 to 3 disclose that, in order to improve battery performance such as charge/discharge cycle characteristics, attention is focused on the lattice distortion of the crystal structure of the positive electrode active material, and the distortion is controlled within a specific range.
  • Patent Documents 1 to 3 still have a lot of room for improvement in terms of increasing capacity.
  • the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present disclosure is a positive electrode active material for a non-aqueous electrolyte secondary battery having a crystal structure belonging to space group R-3m, and is represented by a composition formula Li 1+a Ni b Mn c X d O e , in which X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Ni, and Mn, a ⁇ 1.15, 0.35 ⁇ b ⁇ 0.70, 0.30 ⁇ c ⁇ 0.65, 0 ⁇ d ⁇ 0.07, and e are values that satisfy electrical neutrality, and the value ( ⁇ ) obtained by multiplying the Ni mixing rate ⁇ determined by Rietveld analysis and the strain ⁇ determined by the Williamson-Hall method is 0.090 or less.
  • the nonaqueous electrolyte secondary battery according to the present disclosure comprises a positive electrode containing the above-mentioned positive electrode active material, a negative electrode, and a nonaqueous electrolyte.
  • the positive electrode active material disclosed herein can achieve high capacity non-aqueous electrolyte secondary batteries.
  • FIG. 1 is a longitudinal sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention
  • the inventors have discovered that in a positive electrode active material having a crystal structure belonging to the space group R-3m, the charge/discharge capacity of the battery is significantly increased when the value ( ⁇ ) obtained by multiplying the mixing rate ⁇ , which represents the proportion of Ni that occupies the Li site of the crystal structure, and the distortion ⁇ , which indicates the non-uniformity of the spacing of the crystal lattice planes, is 0.090 or less.
  • the inventors have discovered that in a layered rock salt structure belonging to the space group R-3m, the mixing rate ⁇ and distortion ⁇ have a significant effect on the discharge capacity, and that controlling the value of ⁇ to 0.090 or less results in a specific improvement in the discharge capacity.
  • the influence of the mixing rate ⁇ and distortion ⁇ on the discharge capacity becomes large, and the effect of controlling the value of ⁇ to 0.090 or less becomes significant.
  • the material cost of batteries it is required to reduce the Ni content of the positive electrode active material, but if the Ni content is reduced, it becomes difficult to increase the capacity of the battery.
  • the positive electrode active material according to the present disclosure is extremely useful in achieving both low cost and high capacity of batteries. Note that the value of ⁇ varies greatly depending on the synthesis conditions of the positive electrode active material, so adjusting the value of ⁇ to the desired value cannot be achieved unless the synthesis conditions are strictly controlled with attention to this value.
  • a nonaqueous electrolyte secondary battery 10 is exemplified, which is a cylindrical battery in which a wound electrode body 14 is housed in a cylindrical exterior can 16 with a bottom, but the exterior body of the battery is not limited to a cylindrical exterior can.
  • Other embodiments of the nonaqueous electrolyte secondary battery according to the present disclosure include, for example, a prismatic battery with a prismatic exterior can, a coin-shaped battery with a coin-shaped exterior can, and a pouch-type battery with an exterior body composed of a laminate sheet including a metal layer and a resin layer.
  • the electrode body is not limited to a wound type, and may be a laminated type electrode body in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators between them.
  • the nonaqueous electrolyte secondary battery 10 includes a wound electrode assembly 14, a nonaqueous electrolyte, and an outer can 16 that contains the electrode assembly 14 and the nonaqueous electrolyte.
  • the nonaqueous electrolyte secondary battery 10 is, for example, a lithium ion secondary battery.
  • the electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed therebetween.
  • the outer can 16 is a cylindrical metal container with a bottom that is open at one axial end, and the opening of the outer can 16 is closed by a sealing body 17.
  • the sealing body 17 side of the battery is referred to as the top
  • the bottom side of the outer can 16 is referred to as the bottom.
  • the non-aqueous electrolyte has lithium ion conductivity.
  • the non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.
  • the liquid electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • a non-aqueous solvent for example, esters, ethers, nitriles, amides, and mixed solvents of two or more of these are used as the non-aqueous solvent.
  • the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these.
  • the non-aqueous solvent may contain a halogen-substituted product (e.g., fluoroethylene carbonate, etc.) in which at least a part of the hydrogen of these solvents is replaced with a halogen atom such as fluorine.
  • a halogen-substituted product e.g., fluoroethylene carbonate, etc.
  • a lithium salt such as LiPF6 is used as the electrolyte salt.
  • the solid electrolyte for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. can be used.
  • the inorganic solid electrolyte a material known in all-solid-state lithium ion secondary batteries, etc. (for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, etc.) can be used.
  • the polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer.
  • the matrix polymer for example, a polymer material that absorbs a non-aqueous solvent and gels is used.
  • the polymer material for example, a fluororesin, an acrylic resin, a polyether resin, etc. can be used.
  • the positive electrode 11, negative electrode 12, and separator 13 that make up the electrode body 14 are all long, strip-like bodies that are wound in a spiral shape and stacked alternately in the radial direction of the electrode body 14.
  • the negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the length direction and width direction than the positive electrode 11.
  • the separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11.
  • the electrode body 14 has a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.
  • Insulating plates 18, 19 are arranged above and below the electrode body 14.
  • the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the insulating plate 19 and extends toward the bottom side of the outer can 16.
  • the positive electrode lead 20 is connected to the underside of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal.
  • the negative electrode lead 21 is connected to the inner bottom inner surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.
  • a gasket 28 is provided between the exterior can 16 and the sealing body 17 to ensure airtightness inside the battery.
  • the exterior can 16 has a grooved portion 22 formed with a portion of the side surface that protrudes inward to support the sealing body 17.
  • the grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the exterior can 16, and supports the sealing body 17 on its upper surface.
  • the sealing body 17 is fixed to the top of the exterior can 16 by the grooved portion 22 and the open end of the exterior can 16 that is crimped against the sealing body 17.
  • the sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked.
  • Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to each other.
  • the lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges.
  • the positive electrode 11 has a positive electrode core and a positive electrode mixture layer disposed on the positive electrode core.
  • a foil of a metal stable in the potential range of the positive electrode 11, such as aluminum, an aluminum alloy, stainless steel, or titanium, or a film having the metal disposed on the surface layer can be used.
  • the positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder, and is preferably provided on both sides of the positive electrode core.
  • the positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.
  • Examples of the conductive agent contained in the positive electrode mixture layer include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, metal fibers, metal powders, conductive whiskers, etc.
  • carbon black such as acetylene black and ketjen black
  • graphite carbon nanotubes (CNT)
  • carbon nanofibers carbon nanofibers
  • graphene carbon nanofibers
  • metal fibers graphene
  • metal powders metal powders
  • conductive whiskers etc.
  • One type of conductive agent may be used alone, or multiple types may be used in combination.
  • the content of the conductive agent is, for example, 0.1% by mass or more and 5% by mass or less with respect to the mass of the positive electrode mixture layer.
  • binder contained in the positive electrode mixture layer examples include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), olefin resins such as polyethylene, polypropylene, ethylene-propylene-isoprene copolymer, and ethylene-propylene-butadiene copolymer, and acrylic resins such as polyacrylonitrile (PAN), polyimide, polyamide, and ethylene-acrylic acid copolymer. These resins may also be used in combination with carboxymethylcellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.
  • CMC carboxymethylcellulose
  • PEO polyethylene oxide
  • One type of binder may be used alone, or multiple types may be used in combination.
  • the content of the binder is, for example, 0.1% by mass or more and 5% by mass or less with respect to the mass of the positive electrode mixture layer.
  • the positive electrode active material has a crystal structure belonging to the space group R-3m and is a lithium transition metal composite oxide represented by the composition formula Li 1 + a Ni b Mn c X d O e .
  • X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Ni, and Mn, and a ⁇ 1.15, 0.35 ⁇ b ⁇ 0.70, 0.30 ⁇ c ⁇ 0.65, 0 ⁇ d ⁇ 0.07, and e are values that satisfy electrical neutrality.
  • the composite oxide constituting the positive electrode active material contains Li, Ni, and Mn as essential elements.
  • the composition of the positive electrode active material can be measured using an ICP emission spectrometer (for example, iCAP6300 manufactured by Thermo Fisher Scientific).
  • the positive electrode active material has a layered rock salt structure belonging to the space group R-3m, has a composition that satisfies the above composition formula, and is characterized in that the product ( ⁇ ) of the mixing ratio ⁇ , which indicates the proportion of Ni that enters the Li site of the crystal structure as determined by Rietveld analysis, and the distortion ⁇ , which indicates the non-uniformity of the spacing of the crystal lattice planes as determined by the Williamson-Hall method, is 0.090 or less. When the value of ⁇ is 0.090 or less, the charge/discharge capacity is significantly improved.
  • the molar ratio (b) of Ni is 0.35 or more and 0.70 or less (0.35 ⁇ b ⁇ 0.70).
  • the molar ratio (c) of Mn is 0.30 or more and 0.65 or less (0.30 ⁇ c ⁇ 0.65).
  • the content of Ni is preferably 35 mol% or more and 70 mol% or less with respect to the total number of moles of metal elements excluding Li, and is equal to or greater than the content of Mn.
  • the Ni molar ratio (b) is preferably 0.40 or more, more preferably 0.45 or more, and particularly preferably 0.50 or more. From the viewpoint of reducing material costs, the Ni molar ratio (b) is preferably 0.65 or less, and more preferably 0.60 or less. An example of a suitable range for the Ni molar ratio (b) is 0.45 ⁇ b ⁇ 0.65, or 0.50 ⁇ b ⁇ 0.60. In this case, it is possible to achieve both low cost and high capacity to a higher degree.
  • the molar ratio (c) of Mn is preferably 0.35 or more, and more preferably 0.40 or more.
  • the molar ratio (c) of Mn is preferably 0.60 or less.
  • An example of a suitable range for the molar ratio (c) of Mn is 0.35 ⁇ b ⁇ 0.60, or 0.40 ⁇ b ⁇ 0.60. In this case, it is possible to achieve both low cost and high capacity to a higher degree.
  • X is, for example, at least one element selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al.
  • the molar ratio (d) of X is preferably 0.07 or less (0 ⁇ d ⁇ 0.07), more preferably 0.05 or less, and particularly preferably 0.03 or less.
  • the molar ratio (e) of O is a value that satisfies electrical neutrality. In other words, it is a value that satisfies the valence of O in the positive electrode active material.
  • the molar ratio (e) of O is, for example, 2.00 or more and 2.15 or less (2.00 ⁇ e ⁇ 2.15).
  • the positive electrode active material has a composition represented by the above composition formula, and is mainly composed of a complex oxide (hereinafter referred to as "Li-Ni-Mn complex oxide") in which the above value of ⁇ is 0.090 or less.
  • the main component means the component that has the highest mass ratio among the components of the positive electrode active material.
  • a complex oxide other than the Li-Ni-Mn complex oxide may be used as the positive electrode active material, but the content of the Li-Ni-Mn complex oxide is preferably 50 mass% or more, and may be substantially 100 mass%.
  • the Li-Ni-Mn composite oxide is, for example, a secondary particle formed by agglomeration of a plurality of primary particles.
  • An example of the volume-based median diameter (D50) of the Li-Ni-Mn composite oxide is 1 ⁇ m or more and 30 ⁇ m or less, or 3 ⁇ m or more and 20 ⁇ m or less.
  • the D50 of the composite oxide is a particle size at which the volume integrated value is 50% in the particle size distribution measured by the laser diffraction scattering method.
  • the BET specific surface area of the Li-Ni-Mn composite oxide is, for example, 0.1 m 2 /g or more and 10 m 2 /g or less, or 0.5 m 2 /g or more and 5 m 2 /g or less.
  • the BET specific surface area of the composite oxide is measured according to the BET method (nitrogen adsorption method) described in JIS R1626. If the D50 and the BET specific surface area are within the range, it is easy to
  • the Li-Ni-Mn composite oxide has a layered rock-salt structure belonging to the space group R-3m, and the product of the Ni mixing ratio ⁇ and the strain ⁇ ( ⁇ x ⁇ ) is 0.090 or less.
  • the Ni mixing ratio ⁇ is the ratio of the amount of Ni occupying the Li layer of the layered rock-salt structure to the total amount of Ni, and is determined by Rietveld analysis.
  • the strain ⁇ indicates the non-uniformity of the lattice spacing of the crystal, and is determined by the Williamson-Hall method.
  • the powder X-ray diffraction pattern of the Li-Ni-Mn composite oxide is obtained using a desktop X-ray diffractometer (manufactured by Rigaku Corporation, product name "MiniFlex600”), and the diffracted X-rays are detected by a high-speed one-dimensional detector (D/teX Ultra 2).
  • the measurement conditions using the above X-ray diffraction device are as follows.
  • X-ray source CuK ⁇ ray Tube voltage: 40 kV Tube current: 15mA
  • the mixing ratio ⁇ in the crystal structure of Li-Ni-Mn composite oxide is calculated by dividing the amount of Ni in the Li site refined by Rietveld analysis using Rigaku's analysis software "Smartlab Studio 2" by the total amount of Ni in the structure.
  • the Li site in the Rietveld analysis is the 3b site (0,0,0.5) in the layered rock salt structure (R-3m), and the transition metal site is the 3a site (0,0,0).
  • the distortion ⁇ in the crystal structure of Li-Ni-Mn composite oxide is calculated by the Williamson-Hall method using the 003, 101, 104, 015, and 113 diffraction lines in Smartlab Studio 2.
  • the value obtained by multiplying the mixing rate ⁇ and the strain ⁇ ( ⁇ ) may be 0.090 or less, but is preferably 0.072 or less, and more preferably 0.055 or less.
  • ⁇ there is no particular lower limit to the value of ⁇ , but it is preferably 0.002 or more, and more preferably 0.005 or more.
  • An example of a suitable range for the value of ⁇ is 0.002 or more and 0.072 or less, or 0.005 or more and 0.055 or less. In this case, it is possible to achieve both low cost and high capacity to a higher degree.
  • the suitable value of ⁇ also changes slightly.
  • the value of ⁇ is, for example, 0.035 or more and 0.090 or less, or 0.040 or more and 0.055 or less.
  • the value of ⁇ is, for example, 0.002 or more and 0.040 or less, or 0.005 or more and 0.035 or less.
  • the mixing ratio ⁇ is preferably 0.05 or more and 0.20 or less.
  • the distortion ⁇ is preferably 0.02 or more and 0.50 or less, and more preferably 0.05 or more and 0.30 or less.
  • the Li-Ni-Mn composite oxide can be synthesized, for example, by mixing a composite hydroxide or composite oxide containing Ni, Mn, etc. with a lithium raw material and calcining the mixture.
  • the composite hydroxide containing Ni, Mn, etc. can be obtained by dropping an alkaline solution such as sodium hydroxide into a stirred solution of a metal salt containing Ni, Mn, etc., and adjusting the pH to the alkaline side (for example, 8.5 to 12.5) to cause precipitation (coprecipitation).
  • the composite hydroxide can be calcined to obtain a composite oxide containing Ni, Mn, etc.
  • lithium raw material examples include Li2CO3 , LiOH , Li2O2 , Li2O , LiNO3 , LiNO2 , Li2SO4 , LiOH.H2O , LiH, LiF, etc.
  • the composite hydroxide or composite oxide containing Ni, Mn, etc. and the lithium raw material are preferably mixed in such a ratio that the molar ratio of the total amount of metal elements such as Ni, Mn, etc. to Li is 1:1.01 to 1:1.12.
  • the sintering conditions are important. That is, in the synthesis process of Li-Ni-Mn composite oxide, it is necessary to sinter the mixture of the raw materials so that the value of ⁇ is 0.090 or less.
  • the mixture of raw materials is sintered in the air or in an oxygen stream using a sintering furnace.
  • the sintering temperature is preferably a high temperature of 800°C or higher when the Ni content is about 50 mol% relative to the total number of moles of metal elements in the composite oxide.
  • the required sintering temperature changes depending on the composition of the raw materials, such as the Ni content. For example, if the Ni content is high, the sintering temperature may be lowered. For this reason, the value of ⁇ cannot be adjusted to the desired value unless the conditions are strictly controlled with attention to this value.
  • the firing temperature is preferably 800°C or higher and 1100°C or lower.
  • the heating rate is, for example, 0.3°C/min or higher and 3.0°C/min or lower, or 0.5°C/min or higher and 2.0°C/min or lower.
  • the firing time may be 3 hours or higher and 10 hours or lower.
  • the firing time means the time from when the temperature of the firing furnace reaches the maximum temperature of the firing process to when the firing ends and cooling begins.
  • the fired product may be rapidly cooled in the air by being removed from the firing furnace.
  • the Li-Ni-Mn composite oxide can be obtained, for example, by rapidly cooling the fired product in the air, washing with water and drying as necessary, and pulverizing it by a known method.
  • the sintering temperature is preferably 900°C or more and 1000°C or less. In this case, for example, if the sintering temperature is 850°C, the value of ⁇ cannot be made 0.090 or less, and high capacity cannot be achieved.
  • the negative electrode 12 has a negative electrode core and a negative electrode mixture layer disposed on the negative electrode core.
  • a foil of a metal stable in the potential range of the negative electrode 12, such as copper, copper alloy, stainless steel, nickel, or nickel alloy, or a film having the metal disposed on the surface can be used.
  • the negative electrode mixture layer contains a negative electrode active material and a binder, and is preferably provided on both sides of the negative electrode core.
  • the negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core.
  • the negative electrode mixture layer may contain a conductive agent such as CNT.
  • a carbon material that reversibly absorbs and releases lithium ions is generally used as the negative electrode active material.
  • elements that alloy with Li, such as Si and Sn, and materials containing these elements may also be used as the negative electrode active material.
  • silicon-containing materials that contain Si are preferable.
  • lithium titanate which has a higher charge/discharge potential with respect to metallic lithium than carbon materials, may also be used as the negative electrode active material.
  • One type of negative electrode active material may be used alone, or multiple types may be used in combination.
  • the carbon material functioning as the negative electrode active material is, for example, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, and hard carbon.
  • artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB), natural graphite such as flake graphite, massive graphite, and earthy graphite, or a mixture of these.
  • silicon-containing materials functioning as the negative electrode active material include silicon alloys, silicon compounds, and composite materials containing Si.
  • a suitable silicon-containing material is a composite particle containing an ion-conducting phase and a Si phase dispersed in the ion-conducting phase.
  • the binder contained in the negative electrode mixture layer may be fluororesin, olefin resin, PAN, polyimide, polyamide, acrylic resin, etc., but polyvinyl acetate, styrene-butadiene rubber (SBR), etc. may also be used. Of these, it is preferable to use SBR.
  • SBR styrene-butadiene rubber
  • One type of binder may be used alone, or multiple types may be used in combination.
  • the negative electrode mixture layer contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. These function as thickeners in the negative electrode mixture slurry.
  • the content of the binder is, for example, 0.1% by mass or more and 5% by mass or less with respect to the mass of the negative electrode mixture layer.
  • a porous sheet having ion permeability and insulating properties is used for the separator 13.
  • the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • the material of the separator 13 is preferably a polyolefin such as polyethylene or polypropylene, or cellulose.
  • the separator 13 may have a single layer structure or a multi-layer structure.
  • a highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13.
  • a filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.
  • inorganic fillers include oxides and phosphate compounds containing metal elements such as Ti, Al, Si, and Mg.
  • the filler layer can be formed by applying a slurry containing the filler to the surface of the positive electrode 11, the negative electrode 12, or the separator 13.
  • the Li-Ni-Mn composite oxide was used as the positive electrode active material.
  • the positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed in a solid content mass ratio of 92:5:3, and a positive electrode mixture slurry was prepared using N-methyl-2-pyrrolidone (NMP) as a dispersion medium.
  • NMP N-methyl-2-pyrrolidone
  • a non-aqueous electrolyte solution was prepared by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solvent prepared by mixing fluoroethylene carbonate (FEC) and methyl propionate (FMP) in a volume ratio of 1:3 to a concentration of 1 mol/L.
  • LiPF 6 lithium hexafluorophosphate
  • FEC fluoroethylene carbonate
  • FMP methyl propionate
  • test cell A lithium metal foil was used as the negative electrode, and the positive and negative electrodes were arranged to face each other with a separator interposed therebetween to form an electrode assembly.
  • This electrode assembly and the nonaqueous electrolyte were placed in a coin-shaped outer can, and the opening of the outer can was sealed with a gasket and a sealer to prepare a test cell (nonaqueous electrolyte secondary battery).
  • Example 3 A positive electrode active material and a test cell were prepared in the same manner as in Example 2, except that in the synthesis step of the Li-Ni-Mn composite oxide, the baking temperature was changed to 1000° C. and the baking time was changed to 10 hours.
  • the resulting mixture was heated at a temperature increase rate of 1
  • Example 1 A positive electrode active material and a test cell were prepared in the same manner as in Example 1, except that in the synthesis step of the Li-Ni-Mn composite oxide, the baking temperature was changed to 850° C. and the baking time was changed to 5 hours.
  • Example 2 A positive electrode active material and a test cell were prepared in the same manner as in Example 2, except that in the synthesis step of the Li-Ni-Mn composite oxide, the baking temperature was changed to 850° C. and the baking time was changed to 10 hours.
  • Example 3 A positive electrode active material and a test cell were prepared in the same manner as in Example 2, except that in the synthesis step of the Li-Ni-Mn composite oxide, the baking temperature was changed to 850° C. and the baking time was changed to 3 hours.
  • Ni mixing rate ⁇ and distortion ⁇ were determined for each Li-Ni-Mn composite oxide in the examples and comparative examples using the above method, and these values and the value of ⁇ are shown in Table 1.
  • test cells of the examples have a higher capacity than the test cells of the comparative examples. That is, in the layered rock salt structure of Li-Ni-Mn composite oxide, when the value obtained by multiplying the mixing rate ⁇ and the strain ⁇ ( ⁇ ) is 0.090 or less, the battery capacity can be greatly improved. When the value of ⁇ exceeds 0.090, as in the case of the positive electrode active material of the comparative example, it is not possible to achieve a high capacity like that achieved when the positive electrode active material of the examples is used.
  • the value of ⁇ of Li-Ni-Mn composite oxide varies greatly depending on the synthesis conditions of the composite oxide.
  • the value of ⁇ varies greatly (Example 2: 0.0872, Comparative Example 3: 0.1100).
  • the discharge capacity also differs greatly (Example 2: 174.0 mAh/g, Comparative Example 3: 153.9 mAh/g).
  • the sintering temperature is increased to 1000°C and the sintering time is extended, the value of ⁇ becomes 0.0423 and the discharge capacity becomes 189.9 mAh/g (see Example 3).
  • Configuration 1 A positive electrode active material for a non-aqueous electrolyte secondary battery having a crystal structure belonging to space group R-3m, the positive electrode active material being represented by a composition formula Li1 + aNibMncXdOe , in which X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Ni, and Mn, a ⁇ 1.15, 0.35 ⁇ b ⁇ 0.70, 0.30 ⁇ c ⁇ 0.65, 0 ⁇ d ⁇ 0.07, and e are values that satisfy electrical neutrality, and a value ( ⁇ ) obtained by multiplying a Ni mixing rate ⁇ determined by Rietveld analysis by a strain ⁇ determined by the Williamson-Hall method is 0.090 or less.
  • Configuration 2 The positive electrode active material for a nonaqueous electrolyte secondary battery according to configuration 1, wherein a value ( ⁇ ) obtained by multiplying the mixing rate ⁇ and the strain ⁇ is 0.002 or more and 0.072 or less.
  • Configuration 3 The positive electrode active material for a non-aqueous electrolyte secondary battery according to configuration 1 or 2, wherein the mixing ratio ⁇ is 0.05 or more and 0.20 or less.
  • Configuration 4 A positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of configurations 1 to 3, wherein in the composition formula Li 1+a Ni b Mn c X d O e , the molar ratio (b) of Ni is 0.50 ⁇ b ⁇ 0.60.
  • Configuration 5 A positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4 , wherein in the composition formula Li1 + aNibMncXdOe , X is at least one selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al.
  • Configuration 6 The positive electrode active material for a non-aqueous electrolyte secondary battery according to Configuration 5, wherein X is at least one selected from Al and Co in the composition formula Li1 + aNibMncXdOe .
  • Configuration 7 A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material according to any one of configurations 1 to 6, a negative electrode, and a non-aqueous electrolyte.

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PCT/JP2024/001565 2023-01-26 2024-01-22 非水電解質二次電池用正極活物質および非水電解質二次電池 Ceased WO2024157907A1 (ja)

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