EP4688665A1 - Cathode active materials comprising cobalt, and way of manufacture - Google Patents

Cathode active materials comprising cobalt, and way of manufacture

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Publication number
EP4688665A1
EP4688665A1 EP24714515.4A EP24714515A EP4688665A1 EP 4688665 A1 EP4688665 A1 EP 4688665A1 EP 24714515 A EP24714515 A EP 24714515A EP 4688665 A1 EP4688665 A1 EP 4688665A1
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EP
European Patent Office
Prior art keywords
range
cobalt
cathode active
active material
crystallites
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24714515.4A
Other languages
German (de)
French (fr)
Inventor
Jacob HAAG
Bohang SONG
Ke-Bin LOW
James A Sioss
Kristi L MAJNI
Plousia VASSILARAS
Carsten Sueling
Philipp KURZHALS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
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Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP4688665A1 publication Critical patent/EP4688665A1/en
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/80—Compounds containing nickel, with or without oxygen or hydrogen, and containing one or more other elements
    • C01G53/82—Compounds containing nickel, with or without oxygen or hydrogen, and containing two or more other elements
    • 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
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/364—Composites as mixtures
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/60—Compounds characterised by their crystallite size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/50—Agglomerated particles
    • 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
    • C01P2004/52—Particles with a specific particle size distribution highly monodisperse 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
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
    • 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

  • Cathode active materials comprising cobalt, and way of manufacture
  • the present invention relates to cathode active materials comprising
  • base material (A) is a polycrystalline material whose secondary particles are composed of primary particles, and crystallites of cobalt compounds (B) are coated on the outer surface of 90 to 99.5% of the secondary particles, and additional cobalt compound(s) being located at said primary particles forming a concentration gradient, determined by EDX and SEM/TEM imaging.
  • Lithium-ion secondary batteries are modern devices for storing energy. Many application fields have been and are contemplated, from small devices such as mobile phones and laptop computers through car batteries and other batteries for e-mobility. Various components of the batteries have a decisive role with respect to the performance of the battery such as the electrolyte, the electrode materials, and the separator. Particular attention has been paid to the cathode materials. Several materials have been suggested, such as lithium iron phosphates, lithium cobalt oxides, and lithium nickel cobalt manganese oxides. Although extensive research has been performed, the solutions found so far still leave room for improvement.
  • cathode active materials that contain 60 mol-% or more of Ni, referring to the total content of metals other than lithium.
  • cathode active materials with a high electrochemical performance.
  • cathode active materials with a low tendency of cracking upon repeated cycling. It was found that an improved percentage of coated particles is advantageous. Accordingly, the particulate materials as defined at the outset have been found, hereinafter also referred to as inventive cathode active materials and cathode active materials according to the present invention.
  • inventive cathode active material is a particulate material, and it comprises
  • base material (A) a base material according to general formula Lii +x iTMi. x iO2, hereinafter also referred to as “base material (A) or “core (A)” or simply “(A)”, wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Zr, Ti, Zr, Nb, Ta, and W, and x1 is in the range of from zero to 0.2, and
  • Base material (A) and crystallites (B) will be described in more details below.
  • base material (A) has an average particle diameter (D50) in the range of from 3 to 20 pm, preferably from 5 to 16 pm.
  • the average particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy.
  • the particles are usually composed of a plurality of primary particles, and the above particle diameter refers to the secondary particle diameter.
  • traces of ubiquitous metals such as sodium, calcium, iron or zinc, as impurities will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content of the TM or of crystallites (B), respectively.
  • Base material (A) is preferably a nickel-rich cathode active material.
  • the percentage of nickel in the base material may be 50 mole-% or even lower, e.g., 40 mole-%, it is preferred that the molar percentage of nickel in base material is at least 60 mole-%, referring to all metals in TM.
  • TM in the above formula contains at least one of Mn, Co and Al, preferably at least two, e.g., Co and Mn, or Co and Al, or even all three, namely, Mn, Co, and Al.
  • TM may contain at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W.
  • TM is a combination of metals according to general formula (I)
  • variable TM corresponds to general formula (I a)
  • M 2 is at least one of Mg, W, Mo, Ti or Zr.
  • TM corresponds to general formula (I) and x1 in Lii+xiTMi-xiO2 is in the range from -0.05 to 0.2, preferably from zero to 0.1 and even more preferably 0.01 to 0.05.
  • TM corresponds to general formula (I a) and x1 in Lii+xiTMi-xiO2 is in the range of from -0.05 to zero.
  • the cobalt concentration in the secondary particles exhibits a gradient. Then, the cobalt concentration is higher on the outer surface than in the center of the secondary particles, determined by EDX and SEM/TEM imaging.
  • the Co/(Co+Ni) atomic ratio exhibits a gradient at grain boundaries of primary particles, wherein when the primary particles are at the outer surface region of secondary particles the said ratio is in the range of from b/(a+b) to b*b/(a+b) (1 ⁇ 6 ⁇ 10), and wherein when the primary particles are at inner region of secondary particles said ratio is in the range of from b/(a+b) to y*b/(a+b) (1 ⁇ y ⁇ 3), but in any case 5 is larger than y.
  • the variables a and b refer to formula (I).
  • an enrichment of cobalt compound(s) may be observed in voids between primary particles that are close to the outer surface of secondary particles.
  • cobalt compound(s) are enriched at surfaces of said primary particles in the voids between adjacent primary particles.
  • an enrichment of cobalt compound(s) across grain boundaries of two adjacent primary particles may be observed. Both enrichments may be made visible by EDX and SEM/TEM imaging.
  • voids formed of the primary particles close to the outer surface contain a cobalt compound selected from LiCoC>2, CO3O4 and Li y iCoO2 (0 ⁇ y1 ⁇ 0.6).
  • Crystallites (B) comprise of cobalt oxide compounds in which at least some cobalt is in the oxidation state of +III.
  • the oxidation state of cobalt in particles (B) may be determined by X-ray photoelectron spectroscopy (“XPS”), and the location relative to base material (A) may be determined by imaging processes such as transmission electron microscopy (“TEM”) and scanning electron microscopy (“SEM”).
  • the phase type of particles (B) may be determined by high resolution (for example synchrotron source) X-ray powder diffraction (“XRD“).
  • the average molar ratio of lithium to cobalt in crystallites (B) is in the range of from 0.45 to below 1.
  • the molar ratio of lithium to cobalt in crystallites (B) is in the range of from zero to below 1 , or it is one.
  • Crystallites (B) may form a homogeneous layer on the base material (A), or an inhomogeneous layer that exhibits accumulations of crystallites (B) next to non-coated parts.
  • the average oxidation state of cobalt in crystallites (B) is in the range of from +2 to +3, preferably from above +2 to +3 and even more preferably from +2.5 to +3.0.
  • the average oxidation state of cobalt in crystallites (B) is in the range of +III to +IV, preferably from 3.0 to 3.5, even more preferably 3.5.
  • the molar ratio of lithium to cobalt in crystallites (B) is in the range of from zero to 1 , preferably from above zero to below 1.
  • At least some of the cobalt in crystallites (B) is in the oxidation state of +III. This includes the option that all of the cobalt in crystallites (B) is in the oxidation state of +III, for example like in LiCoC . In other embodiments, 50 mol-% of the cobalt is in the oxidation state of +III and the rest is in the oxidation state of + IV, for example in U0.5C0O2 (corresponds to UCO2O4).
  • cobalt in crystallites (B) is in the form of at least one of CO3O4, Li y iCoC>2 (0 ⁇ y1 ⁇ 0.6) with spinel structure, LiCoO2, or LiCo y 2Nii. y 2O2 (0 ⁇ y2 ⁇ 0.6) with a layered structure.
  • CO3O4 and U0.5C0O2 have spinel structures, and LiCoCb is rhombohe- dral.
  • crystallites (B) are not composed of a defined compound but a mixture of several cobalt containing oxides, for example, sub-stoichiometric lithium cobalt oxide compounds, furthermore CO3O4 or U0.5C0O2, with LiCoO2 and CO2O3 as optional components.
  • the weight ratio of base material (A) and crystallites (B) is in the range of from 1000 : 1 to 10 to 1 , preferably 100:1 to 20:1.
  • crystallites (B) have an average diameter (D50) in the range of from 10 nm to 1 pm, preferably 10 nm to 100 nm.
  • the average diameter (D50) may be determined by imaging processes such as TEM and SEM.
  • inventive cathode active materials further comprise aluminum compound(s) and titanium compound(s) or of zirconium compound(s), each being in crystallites (B).
  • crystallites (B) or grain boundaries of base material (A) comprise cobalt and lithium and at least one compound of at least one of Ti, Zr and Al, for example an oxide, oxyhydroxide o hydroxide, oxides being preferred.
  • crystallites (B) or grain boundaries of base material (A) comprise cobalt and lithium and Al and at least one of Ti and Zr as additional elements, and it is preferred that crystallites (B) comprise more Co than any of Al, Ti and Zr.
  • crystallites (B) comprise Al and at least one additional element selected from Ti and Zr
  • individual crystallites (B) may comprise both Li and Co and at least one of Ti, Zr and Al, but in other embodiments, individual particles comprise either cobalt or any of Ti, Zr or Al.
  • the ratio of the molar ratio of Co to the sum of Al and Zr or Ti is in the range of from 2:1 to 50:1.
  • Examples of such compounds of Ti, Zr or Al are TiC>2, Ti2O 3 , TiO(OH)2, TiC aq, AI2O3, AIOOH, AI(OH) 3 , AI 2 O 3 aq, ZrO 2 , Zr(OH) 4 , and ZrO 2 aq.
  • crystallites (B) and grain boundaries of base material (A) do not contain either of Al, Ti or Zr.
  • inventive cathode active materials have a surface (BET) in the range of from 0.1 to 0.1.2 m 2 /g, determined according to DIN-ISO 9277:2003-05.
  • Inventive cathode active show excellent electrochemical performance when implemented into a cathode for a lithium-ion battery.
  • Inventive cathode active materials show a reduced tendency of cracking upon repeated cycling.
  • 20 to 45 % of the secondary particles exhibit cracks after 500 cycles of charging/discharging at 4.2 to 3.0 V in full cell with a graphite anode, at 45°C.
  • Cracks may be determined by SEM imaging of cross sections of disassembled cathode from a cycled cell. Cracked particles are defined as those particles wherein at least one crack is present penetrating from secondary particle surface towards the center, determined on a sample of 500 particles.
  • a further aspect of the present invention refers to electrodes comprising at least one electrode material active according to the present invention. They are particularly useful for lithium-ion batteries. Lithium-ion batteries comprising at least one electrode according to the present invention exhibit a good discharge behavior. Electrodes comprising at least one cathode active material according to the present invention are hereinafter also referred to as inventive cathodes or cathodes according to the present invention.
  • inventive electrodes contain
  • inventive cathodes contain
  • (C) 0.5 to 9.5 % by weight of binder polymer, percentages referring to the sum of (A), (B) and (C).
  • a further aspect of the present invention is directed to a secondary battery containing
  • Cathodes according to the present invention can comprise further components. They can comprise a current collector, such as, but not limited to, an aluminum foil. They can further comprise conductive carbon and a binder.
  • Cathodes according to the present invention contain carbon in electrically conductive modification, in brief also referred to as carbon (B).
  • Carbon (B) can be selected from soot, active carbon, carbon nanotubes, graphene, and graphite. Carbon (B) can be added as such during preparation of electrode materials according to the invention.
  • Suitable binders (C) are preferably selected from organic (co)polymers.
  • Suitable (co)polymers i.e. , homopolymers or copolymers, can be selected, for example, from (co)polymers obtainable by anionic, catalytic or free-radical (co)polymerization, especially from polyethylene, polyacrylonitrile, polybutadiene, polystyrene, and copolymers of at least two comonomers selected from ethylene, propylene, styrene, (meth)acrylonitrile and 1 ,3-butadiene.
  • Polypropylene is also suitable.
  • Polyisoprene and polyacrylates are additionally suitable. Particular preference is given to polyacrylonitrile.
  • polyacrylonitrile is understood to mean not only polyacrylonitrile homopolymers but also copolymers of acrylonitrile with 1 ,3-butadiene or styrene. Preference is given to polyacrylonitrile homopolymers.
  • polyethylene is not only understood to mean homopolyethylene, but also copolymers of ethylene which comprise at least 50 mol% of copolymerized ethylene and up to 50 mol% of at least one further comonomer, for example a-olefins such as propylene, butylene (1-butene), 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-pentene, and also isobutene, vinylaromatics, for example styrene, and also (meth)acrylic acid, vinyl acetate, vinyl propionate, Ci-C -alkyl esters of (meth)acrylic acid, especially methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhe
  • polypropylene is not only understood to mean homopolypropylene, but also copolymers of propylene which comprise at least 50 mol% of copolymerized propylene and up to 50 mol% of at least one further comonomer, for example ethylene and a- olefins such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene and 1-pentene.
  • Polypropylene is preferably isotactic or essentially isotactic polypropylene.
  • polystyrene is not only understood to mean homopolymers of styrene, but also copolymers with acrylonitrile, 1 ,3-butadiene, (meth)acrylic acid, Ci- Cw-alkyl esters of (meth)acrylic acid, divinylbenzene, especially 1 ,3-divinylbenzene, 1 ,2- diphenylethylene and a-methylstyrene.
  • Another preferred binder is polybutadiene.
  • Suitable binders are selected from polyethylene oxide (PEO), cellulose, carboxym ethylcellulose, polyimides and polyvinyl alcohol.
  • binder is selected from those (co)polymers which have an average molecular weight M w in the range from 50,000 to 1 ,000,000 g/mol, preferably to 500,000 g/mol.
  • Binder may be cross-linked or non-cross-linked (co)polymers.
  • binder is selected from halogenated (co)polymers, especially from fluorinated (co)polymers.
  • Halogenated or fluorinated (co)polymers are understood to mean those (co)polymers which comprise at least one (co)polymerized (co)monomer which has at least one halogen atom or at least one fluorine atom per molecule, more preferably at least two halogen atoms or at least two fluorine atoms per molecule.
  • Examples are polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers (PVdF-HFP), vinylidene fluoride-tetrafluoroethylene copolymers, perfluoroalkyl vinyl ether copolymers, ethylene-tetrafluoroethylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers and ethylene-chlorofluoroethylene copolymers.
  • Suitable binders are especially polyvinyl alcohol and halogenated (co)polymers, for example polyvinyl chloride or polyvinylidene chloride, especially fluorinated (co)polymers such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.
  • inventive cathodes may comprise 1 to 15% by weight of binder(s), referring to cathode active material. In other embodiments, inventive cathodes may comprise 0.1 up to less than 1% by weight of binder(s).
  • a further aspect of the present invention is a battery, containing at least one cathode comprising inventive cathode active material, carbon, and binder, at least one anode, and at least one electrolyte.
  • Said anode may contain at least one anode active material, such as carbon (graphite), TiC>2, lithium titanium oxide, silicon or tin.
  • Said anode may additionally contain a current collector, for example a metal foil such as a copper foil.
  • Said electrolyte may comprise at least one non-aqueous solvent, at least one electrolyte salt and, optionally, additives.
  • Non-aqueous solvents for electrolytes can be liquid or solid at room temperature and is preferably selected from among polymers, cyclic or acyclic ethers, cyclic and acyclic acetals and cyclic or acyclic organic carbonates.
  • suitable polymers are, in particular, polyalkylene glycols, preferably poly-Ci-C4- alkylene glycols and in particular polyethylene glycols.
  • Polyethylene glycols can here comprise up to 20 mol% of one or more Ci-C4-alkylene glycols.
  • Polyalkylene glycols are preferably polyalkylene glycols having two methyl or ethyl end caps.
  • the molecular weight M w of suitable polyalkylene glycols and in particular suitable polyethylene glycols can be at least 400 g/mol.
  • the molecular weight M w of suitable polyalkylene glycols and in particular suitable polyethylene glycols can be up to 5 000 000 g/mol, preferably up to 2 000 000 g/mol.
  • Suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1 ,2-dimethoxyethane, 1 ,2-diethoxyethane, with preference being given to 1 ,2-dimethoxyethane.
  • Suitable cyclic ethers are tetrahydrofuran and 1 ,4-dioxane.
  • Suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1 ,1 -dimethoxyethane and 1 ,1 -diethoxyethane.
  • Suitable cyclic acetals are 1 ,3-dioxane and in particular 1 ,3-dioxolane.
  • Suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.
  • Suitable cyclic organic carbonates are compounds according to the general formulae (II) and (III) where R 1 , R 2 and R 3 can be identical or different and are selected from among hydrogen and Ci-C4-alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tertbutyl, with R 2 and R 3 preferably not both being tert-butyl.
  • R 1 is methyl and R 2 and R 3 are each hydrogen, or R 1 , R 2 and R 3 are each hydrogen.
  • Another preferred cyclic organic carbonate is vinylene carbonate, formula (IV).
  • the solvent or solvents is/are preferably used in the water-free state, i.e. with a water content in the range from 1 ppm to 0.1% by weight, which can be determined, for example, by Karl-Fischer titration.
  • Electrolyte (C) further comprises at least one electrolyte salt.
  • Suitable electrolyte salts are, in particular, lithium salts.
  • Preferred electrolyte salts are selected from among LiC(CF 3 SO2)3, LiN(CF 3 SO2)2, LiPF 6 , LiBF 4 , LiCICU, with particular preference being given to LiPFe and LiN(CFsSO2)2.
  • batteries according to the invention comprise one or more separators by means of which the electrodes are mechanically separated.
  • Suitable separators are polymer films, in particular porous polymer films, which are unreactive toward metallic lithium.
  • Particularly suitable materials for separators are polyolefins, in particular film-forming porous polyethylene and film-forming porous polypropylene.
  • Separators composed of polyolefin, in particular polyethylene or polypropylene can have a porosity in the range from 35 to 45%. Suitable pore diameters are, for example, in the range from 30 to 500 nm.
  • separators can be selected from among PET nonwovens filled with inorganic particles.
  • Such separators can have porosities in the range from 40 to 55%. Suitable pore diameters are, for example, in the range from 80 to 750 nm.
  • Batteries according to the invention further comprise a housing which can have any shape, for example cuboidal or the shape of a cylindrical disk or a cylindrical can.
  • a metal foil configured as a pouch is used as housing.
  • Batteries according to the invention display a good discharge behavior, for example at low temperatures (zero °C or below, for example down to -10°C or even less), a very good discharge and cycling behavior.
  • Batteries according to the invention can comprise two or more electrochemical cells that combined with one another, for example can be connected in series or connected in parallel. Connection in series is preferred.
  • at least one of the electrochemical cells contains at least one cathode according to the invention.
  • the majority of the electrochemical cells contains a cathode according to the present invention.
  • all the electrochemical cells contain cathodes according to the present invention.
  • the present invention further relates to the use of batteries according to the invention in appliances, in particular in mobile appliances.
  • mobile appliances are vehicles, for example automobiles, bicycles, aircraft or water vehicles such as boats or ships.
  • Other examples of mobile appliances are those which move manually, for example computers, especially laptops, telephones or electric hand tools, for example in the building sector, especially drills, battery-powered screwdrivers or battery-powered staplers.
  • the present invention further relates to a process for manufacturing inventive cathode active materials, hereinafter also referred to as “inventive process” or “process according to the (present) invention”.
  • inventive process comprises at least three steps, (a), (b), and (c), in the context of the present invention also referred to as step (a) and step (b) and step (c), respectively. Steps (a) and
  • TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x2 is in the range of from zero to 0.25,
  • oxide or (oxy)hydroxide of cobalt contacting said material with an oxide or (oxy)hydroxide of cobalt and, optionally, up to 10 % by vol of water and, optionally, at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al, wherein said oxide or (oxy)hydroxide of cobalt has an average particle diameter (D50) in the range of from 10 nm to 50 pm and a span of the particle diameter distribution in the range of from 0.5 to 3.5,
  • D50 average particle diameter
  • step (c) optionally, removing water from the mixture obtained in step (b),
  • step (d) calcining the intermediate of step (b) or - if applicable - step (c).
  • the inventive process starts off from a cathode active material according to general formula Lii +X 2TMi.x2O 2 , step (a), wherein providing a material according to general formula U1+X2TM1.X2O2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x2 is in the range of from zero to 0.25.
  • Cathode active material according to general formula Lii +X 2TMi. X 2O2 may hereinafter also be referred to as “starting material”.
  • cathode active material according to general formula U1+X2TM1.
  • X2O2 has an average particle diameter (D50) in the range of from 3 to 20 pm, preferably from 5 to 16 pm.
  • the average particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy.
  • the particles are usually composed of agglomerates from primary particles, and the above particle diameter refers to the secondary particle diameter.
  • cathode active material according to general formula U1+X2TM1.X2O2 has a monomodal particle diameter distribution. In another embodiment of the present invention, cathode active material according to general formula U1+X2TM1.X2O2 has a bimodal particle diameter distribution.
  • the starting material has a specific surface (BET), hereinafter also referred to as “BET surface”, in the range of from 0.1 to 1.0 m 2 /g.
  • BET surface may be determined by nitrogen adsorption after outgassing of the sample at 200°C for 30 minutes or more and beyond this in accordance with DIN ISO 9277:2010.
  • the starting material has a moisture content in the range of from 20 to 2,000 ppm, determined by Karl- Fischer titration, preferred are 200 to 1 ,200 ppm.
  • Base material (A) is preferably a nickel-rich cathode active material.
  • the percentage of nickel in base material may be 50 mole-% or even lower, e.g., 40 mole-%, it is preferred that the molar percentage of nickel in base material is at least 60 mole-%, referring to all metals in TM.
  • TM in the above formula contains at least one of Mn, Co and Al, preferably at least two, e.g., Co and Mn, Co and Al, or even Mn, Co, and Al.
  • TM may contain at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W.
  • TM is a combination of metals according to general formula (I)
  • variable TM corresponds to general formula (I a)
  • M 2 is at least one of Mg, W, Mo, Ti or Zr.
  • the starting material provided in step (a) is usually free from conductive carbon, that means that the conductive carbon content of starting material is less than 1% by weight, referring to said starting material, preferably 0.001 to 1.0 % by weight.
  • traces of ubiquitous metals such as sodium, calcium, iron or zinc, as impurities will not be taken into account. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content of the starting material.
  • step (b) said starting material is contacted with an oxide or (oxy) hydroxi de of cobalt and, optionally, up to 10 % by vol of water and, optionally, at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al, wherein said oxide or (oxy) hydroxi de of cobalt has an average particle diameter (D50) in the range of from 10 nm to 50 pm and a span of the particle diameter distribution in the range of from 0.5 to 3.5, followed by mixing.
  • D50 average particle diameter
  • step (b) no compound of lithium such as LiNOs or U2SO4 or LiOH or U2CO3 is added.
  • This does not exclude traces of lithium compounds being inadvertently present, for example 0.01 to 0.1 mol-%, referring to TM. Such traces may be present as impurity, for example in insufficiently cleaned vessels or devices.
  • oxides and (oxy)hydroxides of cobalt are CoO, CO3O4, Co(OH)2, CoOOH, and non- stoichiometric oxyhydroxides of cobalt. Preferred are Co(OH)2 and CO3O4.
  • Examples of optionally added oxide or hydroxide or oxyhydroxide of Ti, Zr or Al are TiC>2, Ti2Os, TiO(OH) 2 , TiO 2 aq, AI2O3, AIOOH, AI(OH) 3 , AI 2 O 3 aq, ZrO 2 , Zr(OH) 4 , and ZrO 2 aq.
  • step (b) is performed by adding an aqueous slurry of an oxide or (oxy) hydroxi de of cobalt and, optionally, of at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al to the starting material, followed by mixing.
  • step (b) is performed by adding an aqueous slurry of an oxide or (oxy) hydroxi de of cobalt and one oxide or hydroxide or oxyhydroxide of Ti, Zr and/or Al to the starting material, followed by mixing, wherein the molar amount of Co is higher than the molar amount of Ti, Zr or Al, respectively. Even more preferably, the molar amount of Co is higher than the molar amount of Ti, Zr and Al.
  • step (b) is performed in a mixer, for example a paddle mixer, a plough-share mixer, a free-fall mixer, a roller mill, or a high-shear mixer.
  • Free fall mixers are using the gravitational force to achieve mixing.
  • High-shear mixers and ploughshare mixers are preferred.
  • the mixer operates in step (b) with a speed in the range of from 5 to 500 revolutions per minute (“rpm”), preferred are 5 to 60 rpm.
  • rpm revolutions per minute
  • a free-fall mixer from 5 to 25 rpm are more preferred and 5 to 10 rpm are even more preferred.
  • a plough-share mixer 50 to 400 rpm are preferred and 100 to 250 rpm are even more preferred.
  • 100 to 950 rpm of the agitator and 100 to 3,750 rpm of the chopper are preferred.
  • Step (b) is preferably performed in the dry state, that is without addition of water or of an organic solvent such as glycol.
  • the weight ratio of base material (A) and crystallites (B) is in the range of from 1000 : 1 to 10 : 1 , preferably 100:1 to 20:1.
  • step (b) is in the range of from one minute to 2 hours, preferred are ten minutes to one hour. In one embodiment of the present invention, step (b) is preferred at a temperature in the range of from 10 to 80°C. Even more preferred is ambient temperature.
  • step (b) is performed in an air atmosphere, or under an inert gas such as nitrogen. Ambient air is preferred.
  • step (b) a mixture is obtained.
  • the mixture has the appearance of a moist powder.
  • step (c) water is removed from the mixture obtained in step (b).
  • Said removal may be performed in vacuo, for example at a pressure in the range of from 1 to 50 mbar, at a temperature in the range of from 50 to 150°C, or under ambient pressure, for example at a temperature in the range of from 100 to 175°C. Ambient air is preferred.
  • step (d) is performed at a temperature in the range of from 350 to 850°C, preferably 500 to 750°C.
  • the temperature is ramped up before reaching the desired temperature of from 350 to 850°C, preferably 500 to 750°C.
  • the mixture of step (b) or step (c), if applicable is heated to a temperature to 350 to 550°C and then held constant for a time of 10 min to 4 hours, and then it is raised to 500 to 750°C.
  • the heating rate in step (d) is in the range of from 0.1 to 10 °C/min.
  • step (d) is performed in a roller hearth kiln, a pusher kiln or a rotary kiln or a combination of at least two of the foregoing.
  • Rotary kilns have the advantage of a very good homogenization of the material made therein.
  • different reaction conditions with respect to different steps may be set quite easily.
  • box-type and tubular furnaces and split tube furnaces are feasible as well.
  • step (d) is performed in an oxygen-containing atmosphere, for example in a nitrogen-air mixture, in a rare gas-oxygen mixture, in air, in oxygen or in oxygen-enriched air.
  • the atmosphere in step (b) is selected from air, oxygen and oxygen-enriched air.
  • Oxygen-enriched air may be, for example, a 50:50 by volume mix of air and oxygen.
  • Other options are 1 :2 by volume mixtures of air and oxygen, 1 :3 by volume mixtures of air and oxygen, 2:1 by volume mixtures of air and oxygen, and 3:1 by volume mixtures of air and oxygen.
  • step (d) is carried out under an atmosphere with reduced CO2 content, e.g., a carbon dioxide content in the range of from 0.01 to 500 ppm by weight, preferred are 0.1 to 50 ppm by weight.
  • the CO2 content may be determined by, e.g., optical methods using infrared light. It is even more preferred to perform step (c) under an atmosphere with a carbon dioxide content below detection limit for example with infrared-light based optical methods.
  • step (d) has a duration in the range of from one hour to 30 hours. Preferred are 60 minutes to 8 hours. The cooling time is neglected in this context.
  • the cathode active material so obtained is cooled down before further processing.
  • the cathode active materials so obtained have a surface (BET) in the range of from 0.1 to 1.2 m 2 /g, determined according to DINISO 9277:2003-05.
  • extractable lithium and especially residual lithium is at least partially drawn to the surface and reacted with Co to Co-Li-containing oxide species.
  • a stirred tank reactor was filled with deionized water with ammonium sulfate added (49 g per kg water). The solution was controlled to be 55°C and pH value to be 12 by adding aqueous sodium hydroxide solution. The tank reactor was simultaneously fed with an aqueous transition metal sulfate solution and aqueous sodium hydroxide solution at a flow rate ratio of 1 .8, and a total flow rate resulting in a residence time of 8 hours.
  • the transition metal sulfate solution contained Ni, Co, Mn in a molar ratio of 94 : 3 : 3 and the total transition metal concentration was 1 .65 mol/kg.
  • the aqueous sodium hydroxide solution was a mixture between sodium hydroxide solution (25wt.%) and ammonia solution (25wt.%) in a weight ratio of 6.
  • the pH value 12 was kept by a separate feed of aqueous sodium hydroxide solution. Beginning with the start-up of all feeds, mother liquor was continuously removed. After 27 hours all feed flows were stopped.
  • the mixed transition metal (TM) oxyhydroxide precursor TM-OH.1 was obtained by filtration of resulting suspension, washing with distilled water, drying at 120°C in air, and sieving.
  • B-CAM (pristine): The mixed transition metal oxyhydroxide precursor obtained according to 1.1. was mixed with 1.2 mole-% AI(OH)s and 0.3 mole-% ZrC>2, both mole-% referring to the sum of Ni, Co, and Mn in the TM-OH.1 , and LiOH monohydrate with a Li/TM molar ratio of 1.03. The mixture was hearted to 725°C for 8hrs in a forced flow of oxygen to obtain the cathode active material CAM.P.
  • a high-shear mixer Earth Technica FS-10 High Speed Mixer, was charged with 3000 g B-CAM, 58.4 g of the respective Co(OH)2, 2.4 g AI2O3, and 3.7 g TiC>2. Neither water, organic solvent, nor Li source were added.
  • the agitator was set to 570 rpm and the chopper to 3500 rpm for 10 minutes. Then, a mixed powder was obtained. The mixed powder was heat treated at a top temperature 500°C for 5 hours under oxygen flow in a box-type furnace and then cooled naturally.
  • the resultant CAM.1 was obtained when it cooled down to ambient temperature.
  • SEM/EDX analysis revealed sub-micro sized coating particles of Co compounds (B), which are conformally distributed on CAM.1 particle surface. Higher Co concentration at CAM.1 particle surface in contrast to particle bulk enables to count a coverage ratio of the coated particles vs. the total particles.
  • a SEM/EDX mapping image covering 81 particles was used for counting. In CAM.1 , some 98% of all particles exhibited such features.
  • C-CAM.2 was manufactured and analyzed in the same way as CAM.1 but in step c-(b.2) - instead of (b.1), the CO(OH)2 with a span (D90 - D10)/D50 of 12.3 was used. Only 86% of the particles of C-CAM.2 showed the respective coverage.
  • TEM/EDX analysis on particle cross section of CAM.1 revealed a Co concentration gradient at primary particle surface at both outer and inner region of secondary particle. Furthermore, the said Co gradient is greater for outer surface of primary particle than inner grain boundary between primary particles. The Co gradient is present even at the bulk center region of secondary particle.
  • PVDF binder Solef® 5130
  • NMP Merk
  • binder solution 3 wt.%)
  • graphite SFG6L, 2 wt.%
  • carbon black Super C65, 1 wt.%
  • inventive CAM.1 or comparative cathode active material C-CAM or base material B-CAM 94 wt.% was added and the resulting suspension was mixed again to obtain a lump-free slurry.
  • the solid content of the slurry was adjusted to 65%.
  • the slurry was coated onto Al foil using a rol l-to-rol I coater. Prior to use, all electrodes were calendared. The thickness of cathode material was 70pm, corresponding to 15 mg/cm 2 . All electrodes were dried at 105°C for 7 hours before battery assembly.
  • a base electrolyte was prepared by mixing 12.7 wt.% LiPF 6 , 26.2 wt.% ethylene carbonate (EC), and 61.1 wt.% ethyl methyl carbonate (EMC) (EL base 1), based on the total weight of EL base
  • Coin-type half cells (20 mm in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under 11.1.1 and lithium metal as working and counter electrode, respectively, were assembled in an Ar-filled glove box. The cathode, anode, and separator were superposed in order of cathode // separator // Li foil to produce a half coin cell. Thereafter, 0.15mL of EL base 1 as described under II.2 were added into the coin cell. III. Evaluation of cell performance
  • CAM.1 exhibited less cracks than C-CAM.2.
  • Particle cracking is measured as follows:
  • artificial intelligence is trained to recognize polished cross-section of the particles of cathode active materials, and to ignore sub-surface features of cathode active material particles;

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Abstract

Particulate cathode active materials comprising (A) a base material according to general formula Li1+xTM1-xO2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x is in the range of from zero to 0.2, and (B) crystallites of cobalt compound(s) in which at least some cobalt is in the oxidation state of +III, wherein base material (A) is a polycrystalline material whose secondary particles are composed of primary particles, and crystallites of cobalt compounds (B) are coated on the outer surface of the secondary particles, and cobalt compound(s) are enriched at surfaces of said primary particles in the voids between adjacent primary particles, and wherein of from 90 to 99.5% of said secondary particles exhibit such cobalt compound enrichment, both determined by EDX and SEM/TEM imaging.

Description

Cathode active materials comprising cobalt, and way of manufacture
The present invention relates to cathode active materials comprising
(A) a base material according to general formula Lii+xTMi.xO2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x is in the range of from zero to 0.2, and
(B) crystallites of cobalt compound(s) in which at least some cobalt is in the oxidation state of +III, wherein base material (A) is a polycrystalline material whose secondary particles are composed of primary particles, and crystallites of cobalt compounds (B) are coated on the outer surface of 90 to 99.5% of the secondary particles, and additional cobalt compound(s) being located at said primary particles forming a concentration gradient, determined by EDX and SEM/TEM imaging.
Lithium-ion secondary batteries are modern devices for storing energy. Many application fields have been and are contemplated, from small devices such as mobile phones and laptop computers through car batteries and other batteries for e-mobility. Various components of the batteries have a decisive role with respect to the performance of the battery such as the electrolyte, the electrode materials, and the separator. Particular attention has been paid to the cathode materials. Several materials have been suggested, such as lithium iron phosphates, lithium cobalt oxides, and lithium nickel cobalt manganese oxides. Although extensive research has been performed, the solutions found so far still leave room for improvement.
Currently, a certain interest in so-called Ni-rich cathode active materials may be observed, for example cathode active materials that contain 60 mol-% or more of Ni, referring to the total content of metals other than lithium.
In US 6,921 ,609, a process for making a cobalt-coated cathode active material has been disclosed. The disclosed cobalt-coated cathode active materials show improved electrochemical behaviour compared to non-coated equivalents. However, the percentage of non-coated particles in a sample is high.
It was an objective of the present invention to provide cathode active materials with a high electrochemical performance. In addition, it was an objective to provide cathode active materials with a low tendency of cracking upon repeated cycling. It was found that an improved percentage of coated particles is advantageous. Accordingly, the particulate materials as defined at the outset have been found, hereinafter also referred to as inventive cathode active materials and cathode active materials according to the present invention.
Accordingly, the cathode active material defined at the outset has been found, hereinafter also referred to as inventive cathode active material. Inventive cathode active material is a particulate material, and it comprises
(A) a base material according to general formula Lii+xiTMi.xiO2, hereinafter also referred to as “base material (A) or “core (A)” or simply “(A)”, wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Zr, Ti, Zr, Nb, Ta, and W, and x1 is in the range of from zero to 0.2, and
(B) crystallites of cobalt compound(s), hereinafter also referred to as “crystallites (B)”, in which at least some cobalt is in the oxidation state of +III, wherein base material (A) is a polycrystalline material whose secondary particles are composed of primary particles, and crystallites of cobalt compounds (B) are coated on the outer surface of 90 to 99.5% of the secondary particles, and additional cobalt compound(s) being located at said primary particles forming a concentration gradient, determined by EDX and SEM/TEM imaging.
Base material (A) and crystallites (B) will be described in more details below.
In one embodiment of the present invention base material (A) has an average particle diameter (D50) in the range of from 3 to 20 pm, preferably from 5 to 16 pm. The average particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy. The particles are usually composed of a plurality of primary particles, and the above particle diameter refers to the secondary particle diameter.
Some elements are ubiquitous. In the context of the present invention, traces of ubiquitous metals such as sodium, calcium, iron or zinc, as impurities will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content of the TM or of crystallites (B), respectively.
Base material (A) is preferably a nickel-rich cathode active material. Although the percentage of nickel in the base material may be 50 mole-% or even lower, e.g., 40 mole-%, it is preferred that the molar percentage of nickel in base material is at least 60 mole-%, referring to all metals in TM. TM in the above formula contains at least one of Mn, Co and Al, preferably at least two, e.g., Co and Mn, or Co and Al, or even all three, namely, Mn, Co, and Al.
Optionally, TM may contain at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W.
In one embodiment of the present invention, TM is a combination of metals according to general formula (I)
(NiaCobMnc)i-dMd (I) with a being in the range of from 0.6 to 0.99, preferably from 0.75 to 0.95, more preferably from 0.80 to 0.91 , b being in the range of from 0.005 to 0.2, preferably from 0.001 to 0.1, c being in the range of from 0.005 to 0.2, preferably from 0.001 to 0.1 , and more preferably from 0.04 to 0.1, d being in the range of from zero to 0.1,
M is selected from Al, Mg, Ti, Zr, Nb, Ta and W, and combinations of at least two of the foregoing, preferably Al and Al and at least one of Mg, Ti, Zr, and Nb, and a + b + c = 1.
In another embodiment of the present invention, the variable TM corresponds to general formula (I a)
(Nia*COb*Ale*)i-d*M2ci* (I a) with a* + b* + e* = 1 and a* being in the range of from 0.75 to 0.99, preferably from 0.88 to 0.95, b* being in the range of from 0.005 to 0.2, preferably from 0.025 to 0.1 , e* being in the range of from 0.002 to 0.2, preferably from 0.015 to 0.04, d* being in the range of from zero to 0.1 , preferably from zero to 0.02,
M2 is at least one of Mg, W, Mo, Ti or Zr. In one embodiment of the present invention TM corresponds to general formula (I) and x1 in Lii+xiTMi-xiO2 is in the range from -0.05 to 0.2, preferably from zero to 0.1 and even more preferably 0.01 to 0.05.
In one embodiment of the present invention TM corresponds to general formula (I a) and x1 in Lii+xiTMi-xiO2 is in the range of from -0.05 to zero.
In one embodiment of the present invention, the cobalt concentration in the secondary particles exhibits a gradient. Then, the cobalt concentration is higher on the outer surface than in the center of the secondary particles, determined by EDX and SEM/TEM imaging.
In one embodiment of the present invention, the Co/(Co+Ni) atomic ratio exhibits a gradient at grain boundaries of primary particles, wherein when the primary particles are at the outer surface region of secondary particles the said ratio is in the range of from b/(a+b) to b*b/(a+b) (1 <6<10), and wherein when the primary particles are at inner region of secondary particles said ratio is in the range of from b/(a+b) to y*b/(a+b) (1 <y<3), but in any case 5 is larger than y. The variables a and b refer to formula (I).
In one embodiment of the present invention, in voids between primary particles that are close to the outer surface of secondary particles, an enrichment of cobalt compound(s) may be observed. Especially, cobalt compound(s) are enriched at surfaces of said primary particles in the voids between adjacent primary particles. In addition, an enrichment of cobalt compound(s) across grain boundaries of two adjacent primary particles may be observed. Both enrichments may be made visible by EDX and SEM/TEM imaging.
In one embodiment of the present invention, voids formed of the primary particles close to the outer surface contain a cobalt compound selected from LiCoC>2, CO3O4 and LiyiCoO2 (0<y1<0.6).
Without wishing to be bound by any theory, we assume that some cobalt may diffuse into the crystal lattice of the primary particles where a more cobalt-enriched compound is formed.
Crystallites (B) comprise of cobalt oxide compounds in which at least some cobalt is in the oxidation state of +III. The oxidation state of cobalt in particles (B) may be determined by X-ray photoelectron spectroscopy (“XPS”), and the location relative to base material (A) may be determined by imaging processes such as transmission electron microscopy (“TEM”) and scanning electron microscopy (“SEM”). The phase type of particles (B) may be determined by high resolution (for example synchrotron source) X-ray powder diffraction (“XRD“). In a preferred embodiment, the average molar ratio of lithium to cobalt in crystallites (B) is in the range of from 0.45 to below 1.
In one embodiment of the present invention, the molar ratio of lithium to cobalt in crystallites (B) is in the range of from zero to below 1 , or it is one.
Crystallites (B) may form a homogeneous layer on the base material (A), or an inhomogeneous layer that exhibits accumulations of crystallites (B) next to non-coated parts.
In one embodiment of the present invention, the average oxidation state of cobalt in crystallites (B) is in the range of from +2 to +3, preferably from above +2 to +3 and even more preferably from +2.5 to +3.0.
In another embodiment of the present invention, the average oxidation state of cobalt in crystallites (B) is in the range of +III to +IV, preferably from 3.0 to 3.5, even more preferably 3.5.
The molar ratio of lithium to cobalt in crystallites (B) is in the range of from zero to 1 , preferably from above zero to below 1.
At least some of the cobalt in crystallites (B) is in the oxidation state of +III. This includes the option that all of the cobalt in crystallites (B) is in the oxidation state of +III, for example like in LiCoC . In other embodiments, 50 mol-% of the cobalt is in the oxidation state of +III and the rest is in the oxidation state of + IV, for example in U0.5C0O2 (corresponds to UCO2O4).
In one embodiment of the present invention, cobalt in crystallites (B) is in the form of at least one of CO3O4, LiyiCoC>2 (0<y1<0.6) with spinel structure, LiCoO2, or LiCoy2Nii.y2O2 (0<y2<0.6) with a layered structure. CO3O4 and U0.5C0O2 have spinel structures, and LiCoCb is rhombohe- dral.
In a preferred embodiment, crystallites (B) are not composed of a defined compound but a mixture of several cobalt containing oxides, for example, sub-stoichiometric lithium cobalt oxide compounds, furthermore CO3O4 or U0.5C0O2, with LiCoO2 and CO2O3 as optional components.
In one embodiment of the present invention, the weight ratio of base material (A) and crystallites (B) is in the range of from 1000 : 1 to 10 to 1 , preferably 100:1 to 20:1. In one embodiment of the present invention, crystallites (B) have an average diameter (D50) in the range of from 10 nm to 1 pm, preferably 10 nm to 100 nm. The average diameter (D50) may be determined by imaging processes such as TEM and SEM.
In one embodiment of the present invention, inventive cathode active materials further comprise aluminum compound(s) and titanium compound(s) or of zirconium compound(s), each being in crystallites (B).
In one embodiment of the present invention, crystallites (B) or grain boundaries of base material (A) comprise cobalt and lithium and at least one compound of at least one of Ti, Zr and Al, for example an oxide, oxyhydroxide o hydroxide, oxides being preferred. Preferably, crystallites (B) or grain boundaries of base material (A) comprise cobalt and lithium and Al and at least one of Ti and Zr as additional elements, and it is preferred that crystallites (B) comprise more Co than any of Al, Ti and Zr. In embodiments wherein crystallites (B) comprise Al and at least one additional element selected from Ti and Zr, individual crystallites (B) may comprise both Li and Co and at least one of Ti, Zr and Al, but in other embodiments, individual particles comprise either cobalt or any of Ti, Zr or Al.
In one embodiment of the present invention, in crystallites (B) or grain boundaries of base material (A) the ratio of the molar ratio of Co to the sum of Al and Zr or Ti is in the range of from 2:1 to 50:1.
Examples of such compounds of Ti, Zr or Al are TiC>2, Ti2O3, TiO(OH)2, TiC aq, AI2O3, AIOOH, AI(OH)3, AI2O3 aq, ZrO2, Zr(OH)4, and ZrO2 aq.
In another embodiment, crystallites (B) and grain boundaries of base material (A) do not contain either of Al, Ti or Zr.
In one embodiment of the present invention inventive cathode active materials have a surface (BET) in the range of from 0.1 to 0.1.2 m2/g, determined according to DIN-ISO 9277:2003-05.
Inventive cathode active show excellent electrochemical performance when implemented into a cathode for a lithium-ion battery. Inventive cathode active materials show a reduced tendency of cracking upon repeated cycling. In one embodiment, 20 to 45 % of the secondary particles exhibit cracks after 500 cycles of charging/discharging at 4.2 to 3.0 V in full cell with a graphite anode, at 45°C. Cracks may be determined by SEM imaging of cross sections of disassembled cathode from a cycled cell. Cracked particles are defined as those particles wherein at least one crack is present penetrating from secondary particle surface towards the center, determined on a sample of 500 particles.
A further aspect of the present invention refers to electrodes comprising at least one electrode material active according to the present invention. They are particularly useful for lithium-ion batteries. Lithium-ion batteries comprising at least one electrode according to the present invention exhibit a good discharge behavior. Electrodes comprising at least one cathode active material according to the present invention are hereinafter also referred to as inventive cathodes or cathodes according to the present invention.
In one embodiment of the present invention, inventive electrodes contain
(A) at least one inventive cathode active material,
(B) carbon in electrically conductive form and
(C) a binder.
In a preferred embodiment of the present invention, inventive cathodes contain
(A) 80 to 99 % by weight inventive cathode active material,
(B) 0.5 to 19.5 % by weight of carbon,
(C) 0.5 to 9.5 % by weight of binder polymer, percentages referring to the sum of (A), (B) and (C).
A further aspect of the present invention is directed to a secondary battery containing
(1) at least one electrode according to claim 13,
(2) at least one anode, and
(3) an electrolyte.
Cathodes according to the present invention can comprise further components. They can comprise a current collector, such as, but not limited to, an aluminum foil. They can further comprise conductive carbon and a binder.
Cathodes according to the present invention contain carbon in electrically conductive modification, in brief also referred to as carbon (B). Carbon (B) can be selected from soot, active carbon, carbon nanotubes, graphene, and graphite. Carbon (B) can be added as such during preparation of electrode materials according to the invention.
Suitable binders (C) are preferably selected from organic (co)polymers. Suitable (co)polymers, i.e. , homopolymers or copolymers, can be selected, for example, from (co)polymers obtainable by anionic, catalytic or free-radical (co)polymerization, especially from polyethylene, polyacrylonitrile, polybutadiene, polystyrene, and copolymers of at least two comonomers selected from ethylene, propylene, styrene, (meth)acrylonitrile and 1 ,3-butadiene. Polypropylene is also suitable. Polyisoprene and polyacrylates are additionally suitable. Particular preference is given to polyacrylonitrile.
In the context of the present invention, polyacrylonitrile is understood to mean not only polyacrylonitrile homopolymers but also copolymers of acrylonitrile with 1 ,3-butadiene or styrene. Preference is given to polyacrylonitrile homopolymers.
In the context of the present invention, polyethylene is not only understood to mean homopolyethylene, but also copolymers of ethylene which comprise at least 50 mol% of copolymerized ethylene and up to 50 mol% of at least one further comonomer, for example a-olefins such as propylene, butylene (1-butene), 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-pentene, and also isobutene, vinylaromatics, for example styrene, and also (meth)acrylic acid, vinyl acetate, vinyl propionate, Ci-C -alkyl esters of (meth)acrylic acid, especially methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and also maleic acid, maleic anhydride and itaconic anhydride. Polyethylene may be HDPE or LDPE.
In the context of the present invention, polypropylene is not only understood to mean homopolypropylene, but also copolymers of propylene which comprise at least 50 mol% of copolymerized propylene and up to 50 mol% of at least one further comonomer, for example ethylene and a- olefins such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene and 1-pentene. Polypropylene is preferably isotactic or essentially isotactic polypropylene.
In the context of the present invention, polystyrene is not only understood to mean homopolymers of styrene, but also copolymers with acrylonitrile, 1 ,3-butadiene, (meth)acrylic acid, Ci- Cw-alkyl esters of (meth)acrylic acid, divinylbenzene, especially 1 ,3-divinylbenzene, 1 ,2- diphenylethylene and a-methylstyrene.
Another preferred binder is polybutadiene.
Other suitable binders are selected from polyethylene oxide (PEO), cellulose, carboxym ethylcellulose, polyimides and polyvinyl alcohol.
In one embodiment of the present invention, binder is selected from those (co)polymers which have an average molecular weight Mw in the range from 50,000 to 1 ,000,000 g/mol, preferably to 500,000 g/mol.
Binder may be cross-linked or non-cross-linked (co)polymers. In a particularly preferred embodiment of the present invention, binder is selected from halogenated (co)polymers, especially from fluorinated (co)polymers. Halogenated or fluorinated (co)polymers are understood to mean those (co)polymers which comprise at least one (co)polymerized (co)monomer which has at least one halogen atom or at least one fluorine atom per molecule, more preferably at least two halogen atoms or at least two fluorine atoms per molecule. Examples are polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers (PVdF-HFP), vinylidene fluoride-tetrafluoroethylene copolymers, perfluoroalkyl vinyl ether copolymers, ethylene-tetrafluoroethylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers and ethylene-chlorofluoroethylene copolymers.
Suitable binders are especially polyvinyl alcohol and halogenated (co)polymers, for example polyvinyl chloride or polyvinylidene chloride, especially fluorinated (co)polymers such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.
Inventive cathodes may comprise 1 to 15% by weight of binder(s), referring to cathode active material. In other embodiments, inventive cathodes may comprise 0.1 up to less than 1% by weight of binder(s).
A further aspect of the present invention is a battery, containing at least one cathode comprising inventive cathode active material, carbon, and binder, at least one anode, and at least one electrolyte.
Embodiments of inventive cathodes have been described above in detail.
Said anode may contain at least one anode active material, such as carbon (graphite), TiC>2, lithium titanium oxide, silicon or tin. Said anode may additionally contain a current collector, for example a metal foil such as a copper foil.
Said electrolyte may comprise at least one non-aqueous solvent, at least one electrolyte salt and, optionally, additives.
Non-aqueous solvents for electrolytes can be liquid or solid at room temperature and is preferably selected from among polymers, cyclic or acyclic ethers, cyclic and acyclic acetals and cyclic or acyclic organic carbonates. Examples of suitable polymers are, in particular, polyalkylene glycols, preferably poly-Ci-C4- alkylene glycols and in particular polyethylene glycols. Polyethylene glycols can here comprise up to 20 mol% of one or more Ci-C4-alkylene glycols. Polyalkylene glycols are preferably polyalkylene glycols having two methyl or ethyl end caps.
The molecular weight Mw of suitable polyalkylene glycols and in particular suitable polyethylene glycols can be at least 400 g/mol.
The molecular weight Mw of suitable polyalkylene glycols and in particular suitable polyethylene glycols can be up to 5 000 000 g/mol, preferably up to 2 000 000 g/mol.
Examples of suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1 ,2-dimethoxyethane, 1 ,2-diethoxyethane, with preference being given to 1 ,2-dimethoxyethane.
Examples of suitable cyclic ethers are tetrahydrofuran and 1 ,4-dioxane.
Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1 ,1 -dimethoxyethane and 1 ,1 -diethoxyethane.
Examples of suitable cyclic acetals are 1 ,3-dioxane and in particular 1 ,3-dioxolane.
Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.
Examples of suitable cyclic organic carbonates are compounds according to the general formulae (II) and (III) where R1, R2 and R3 can be identical or different and are selected from among hydrogen and Ci-C4-alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tertbutyl, with R2 and R3 preferably not both being tert-butyl.
In particularly preferred embodiments, R1 is methyl and R2 and R3 are each hydrogen, or R1, R2 and R3 are each hydrogen.
Another preferred cyclic organic carbonate is vinylene carbonate, formula (IV).
The solvent or solvents is/are preferably used in the water-free state, i.e. with a water content in the range from 1 ppm to 0.1% by weight, which can be determined, for example, by Karl-Fischer titration.
Electrolyte (C) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPFe, LiBF4, LiCIC , LiAsFe, IJCF3SO3, LiC(CnF2n+iSO2)3, lithium imides such as LiN(CnF2n+iSO2)2, where n is an integer in the range from 1 to 20, LiN(SC>2F)2, Li2SiFe, LiSbFe, LiAICU and salts of the general formula (CnF2n+iSO2)tYLi, where m is defined as follows: t = 1 , when Y is selected from among oxygen and sulfur, t = 2, when Y is selected from among nitrogen and phosphorus, and t = 3, when Y is selected from among carbon and silicon.
Preferred electrolyte salts are selected from among LiC(CF3SO2)3, LiN(CF3SO2)2, LiPF6, LiBF4, LiCICU, with particular preference being given to LiPFe and LiN(CFsSO2)2.
In an embodiment of the present invention, batteries according to the invention comprise one or more separators by means of which the electrodes are mechanically separated. Suitable separators are polymer films, in particular porous polymer films, which are unreactive toward metallic lithium. Particularly suitable materials for separators are polyolefins, in particular film-forming porous polyethylene and film-forming porous polypropylene. Separators composed of polyolefin, in particular polyethylene or polypropylene, can have a porosity in the range from 35 to 45%. Suitable pore diameters are, for example, in the range from 30 to 500 nm.
In another embodiment of the present invention, separators can be selected from among PET nonwovens filled with inorganic particles. Such separators can have porosities in the range from 40 to 55%. Suitable pore diameters are, for example, in the range from 80 to 750 nm.
Batteries according to the invention further comprise a housing which can have any shape, for example cuboidal or the shape of a cylindrical disk or a cylindrical can. In one variant, a metal foil configured as a pouch is used as housing.
Batteries according to the invention display a good discharge behavior, for example at low temperatures (zero °C or below, for example down to -10°C or even less), a very good discharge and cycling behavior.
Batteries according to the invention can comprise two or more electrochemical cells that combined with one another, for example can be connected in series or connected in parallel. Connection in series is preferred. In batteries according to the present invention, at least one of the electrochemical cells contains at least one cathode according to the invention. Preferably, in electrochemical cells according to the present invention, the majority of the electrochemical cells contains a cathode according to the present invention. Even more preferably, in batteries according to the present invention all the electrochemical cells contain cathodes according to the present invention.
The present invention further relates to the use of batteries according to the invention in appliances, in particular in mobile appliances. Examples of mobile appliances are vehicles, for example automobiles, bicycles, aircraft or water vehicles such as boats or ships. Other examples of mobile appliances are those which move manually, for example computers, especially laptops, telephones or electric hand tools, for example in the building sector, especially drills, battery-powered screwdrivers or battery-powered staplers.
The present invention further relates to a process for manufacturing inventive cathode active materials, hereinafter also referred to as “inventive process” or “process according to the (present) invention”. The inventive process comprises at least three steps, (a), (b), and (c), in the context of the present invention also referred to as step (a) and step (b) and step (c), respectively. Steps (a) and
(b) and (c) are performed subsequently.
The inventive process comprising the steps of
(a) providing a material according to general formula U1+X2TM1.X2O2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x2 is in the range of from zero to 0.25,
(b) contacting said material with an oxide or (oxy)hydroxide of cobalt and, optionally, up to 10 % by vol of water and, optionally, at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al, wherein said oxide or (oxy)hydroxide of cobalt has an average particle diameter (D50) in the range of from 10 nm to 50 pm and a span of the particle diameter distribution in the range of from 0.5 to 3.5,
(c) optionally, removing water from the mixture obtained in step (b),
(d) calcining the intermediate of step (b) or - if applicable - step (c).
Steps (a) to (d) will be explained in more detail below.
The inventive process starts off from a cathode active material according to general formula Lii+X2TMi.x2O2, step (a), wherein providing a material according to general formula U1+X2TM1.X2O2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x2 is in the range of from zero to 0.25. Cathode active material according to general formula Lii+X2TMi.X2O2 may hereinafter also be referred to as “starting material”.
In one embodiment of the present invention cathode active material according to general formula U1+X2TM1.X2O2 has an average particle diameter (D50) in the range of from 3 to 20 pm, preferably from 5 to 16 pm. The average particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy. The particles are usually composed of agglomerates from primary particles, and the above particle diameter refers to the secondary particle diameter.
In one embodiment of the present invention, cathode active material according to general formula U1+X2TM1.X2O2 has a monomodal particle diameter distribution. In another embodiment of the present invention, cathode active material according to general formula U1+X2TM1.X2O2 has a bimodal particle diameter distribution.
In one embodiment of the present invention, the starting material has a specific surface (BET), hereinafter also referred to as “BET surface”, in the range of from 0.1 to 1.0 m2/g. The BET surface may be determined by nitrogen adsorption after outgassing of the sample at 200°C for 30 minutes or more and beyond this in accordance with DIN ISO 9277:2010.
In one embodiment of the present invention, the starting material has a moisture content in the range of from 20 to 2,000 ppm, determined by Karl- Fischer titration, preferred are 200 to 1 ,200 ppm.
Base material (A) is preferably a nickel-rich cathode active material. Although the percentage of nickel in base material may be 50 mole-% or even lower, e.g., 40 mole-%, it is preferred that the molar percentage of nickel in base material is at least 60 mole-%, referring to all metals in TM.
TM in the above formula contains at least one of Mn, Co and Al, preferably at least two, e.g., Co and Mn, Co and Al, or even Mn, Co, and Al.
Optionally, TM may contain at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W.
In one embodiment of the present invention, TM is a combination of metals according to general formula (I)
(NiaCobMnc)i-dMd (I) wherein a being in the range of from 0.6 to 0.99, preferably from 0.75 to 0.95, more preferably from 0.80 to 0.91 , b being in the range of from 0.005 to 0.2, preferably from 0.01 to 0.1 , c being in the range of from 0.005 to 0.2, preferably from 0.01 to 0.1 , and more preferably from 0.04 to 0.1 , d is in the range of from zero to 0.1 ,
M is selected from Al, Mg, Ti, Zr, Nb, Ta and W, and combinations of at least two of the foregoing, preferably Al and Al and at least one of the foregoing, and a + b + c = 1.
In another embodiment of the present invention, the variable TM corresponds to general formula (I a)
(Nia*COb*Ale*)i-d*M2d* (I a) with a* + b* + e* = 1 and a* being in the range of from 0.75 to 0.99, preferably from 0.88 to 0.95, b* being in the range of from 0.005 to 0.2, preferably from 0.025 to 0.1 , e* being in the range of from 0.002 to 0.2, preferably from 0.015 to 0.04, d* being in the range of from zero to 0.1 , preferably from zero to 0.02,
M2 is at least one of Mg, W, Mo, Ti or Zr.
The starting material provided in step (a) is usually free from conductive carbon, that means that the conductive carbon content of starting material is less than 1% by weight, referring to said starting material, preferably 0.001 to 1.0 % by weight.
Again, some elements are ubiquitous. In the context of the present invention, traces of ubiquitous metals such as sodium, calcium, iron or zinc, as impurities will not be taken into account. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content of the starting material.
In step (b), said starting material is contacted with an oxide or (oxy) hydroxi de of cobalt and, optionally, up to 10 % by vol of water and, optionally, at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al, wherein said oxide or (oxy) hydroxi de of cobalt has an average particle diameter (D50) in the range of from 10 nm to 50 pm and a span of the particle diameter distribution in the range of from 0.5 to 3.5, followed by mixing.
In step (b), no compound of lithium such as LiNOs or U2SO4 or LiOH or U2CO3 is added. This does not exclude traces of lithium compounds being inadvertently present, for example 0.01 to 0.1 mol-%, referring to TM. Such traces may be present as impurity, for example in insufficiently cleaned vessels or devices. Examples of oxides and (oxy)hydroxides of cobalt are CoO, CO3O4, Co(OH)2, CoOOH, and non- stoichiometric oxyhydroxides of cobalt. Preferred are Co(OH)2 and CO3O4.
Examples of optionally added oxide or hydroxide or oxyhydroxide of Ti, Zr or Al are TiC>2, Ti2Os, TiO(OH)2, TiO2 aq, AI2O3, AIOOH, AI(OH)3, AI2O3 aq, ZrO2, Zr(OH)4, and ZrO2 aq.
In one embodiment of the present invention, step (b) is performed by adding an aqueous slurry of an oxide or (oxy) hydroxi de of cobalt and, optionally, of at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al to the starting material, followed by mixing.
In one embodiment of the present invention, step (b) is performed by adding an aqueous slurry of an oxide or (oxy) hydroxi de of cobalt and one oxide or hydroxide or oxyhydroxide of Ti, Zr and/or Al to the starting material, followed by mixing, wherein the molar amount of Co is higher than the molar amount of Ti, Zr or Al, respectively. Even more preferably, the molar amount of Co is higher than the molar amount of Ti, Zr and Al.
In one embodiment of the present invention, step (b) is performed in a mixer, for example a paddle mixer, a plough-share mixer, a free-fall mixer, a roller mill, or a high-shear mixer. Free fall mixers are using the gravitational force to achieve mixing. High-shear mixers and ploughshare mixers are preferred.
In one embodiment of the present invention the mixer operates in step (b) with a speed in the range of from 5 to 500 revolutions per minute (“rpm”), preferred are 5 to 60 rpm. In embodiments wherein a free-fall mixer is applied, from 5 to 25 rpm are more preferred and 5 to 10 rpm are even more preferred. In embodiments wherein a plough-share mixer is applied, 50 to 400 rpm are preferred and 100 to 250 rpm are even more preferred. In the case of high-shear mixers, 100 to 950 rpm of the agitator and 100 to 3,750 rpm of the chopper are preferred.
Step (b) is preferably performed in the dry state, that is without addition of water or of an organic solvent such as glycol.
In one embodiment of the present invention, the weight ratio of base material (A) and crystallites (B) is in the range of from 1000 : 1 to 10 : 1 , preferably 100:1 to 20:1.
In one embodiment of the present invention, the duration of step (b) is in the range of from one minute to 2 hours, preferred are ten minutes to one hour. In one embodiment of the present invention, step (b) is preferred at a temperature in the range of from 10 to 80°C. Even more preferred is ambient temperature.
In one embodiment of the present invention, step (b) is performed in an air atmosphere, or under an inert gas such as nitrogen. Ambient air is preferred.
From step (b), a mixture is obtained. In embodiments in which water is used the mixture has the appearance of a moist powder.
In an optional step (c), water is removed from the mixture obtained in step (b). Said removal may be performed in vacuo, for example at a pressure in the range of from 1 to 50 mbar, at a temperature in the range of from 50 to 150°C, or under ambient pressure, for example at a temperature in the range of from 100 to 175°C. Ambient air is preferred.
In one embodiment of the present invention, step (d) is performed at a temperature in the range of from 350 to 850°C, preferably 500 to 750°C.
In one embodiment of the present invention, the temperature is ramped up before reaching the desired temperature of from 350 to 850°C, preferably 500 to 750°C. For example, first the mixture of step (b) or step (c), if applicable, is heated to a temperature to 350 to 550°C and then held constant for a time of 10 min to 4 hours, and then it is raised to 500 to 750°C.
In one embodiment of the present invention, the heating rate in step (d) is in the range of from 0.1 to 10 °C/min.
In one embodiment of the present invention, step (d) is performed in a roller hearth kiln, a pusher kiln or a rotary kiln or a combination of at least two of the foregoing. Rotary kilns have the advantage of a very good homogenization of the material made therein. In roller hearth kilns and in pusher kilns, different reaction conditions with respect to different steps may be set quite easily. In lab scale trials, box-type and tubular furnaces and split tube furnaces are feasible as well.
In one embodiment of the present invention, step (d) is performed in an oxygen-containing atmosphere, for example in a nitrogen-air mixture, in a rare gas-oxygen mixture, in air, in oxygen or in oxygen-enriched air. In a preferred embodiment, the atmosphere in step (b) is selected from air, oxygen and oxygen-enriched air. Oxygen-enriched air may be, for example, a 50:50 by volume mix of air and oxygen. Other options are 1 :2 by volume mixtures of air and oxygen, 1 :3 by volume mixtures of air and oxygen, 2:1 by volume mixtures of air and oxygen, and 3:1 by volume mixtures of air and oxygen.
In one embodiment of the present invention, step (d) is carried out under an atmosphere with reduced CO2 content, e.g., a carbon dioxide content in the range of from 0.01 to 500 ppm by weight, preferred are 0.1 to 50 ppm by weight. The CO2 content may be determined by, e.g., optical methods using infrared light. It is even more preferred to perform step (c) under an atmosphere with a carbon dioxide content below detection limit for example with infrared-light based optical methods.
In one embodiment of the present invention, step (d) has a duration in the range of from one hour to 30 hours. Preferred are 60 minutes to 8 hours. The cooling time is neglected in this context.
After thermal treatment in accordance with step (d), the cathode active material so obtained is cooled down before further processing.
By performing the inventive process cathode active materials with excellent properties are available through a straightforward process. Preferably, the cathode active materials so obtained have a surface (BET) in the range of from 0.1 to 1.2 m2/g, determined according to DINISO 9277:2003-05.
Without wishing to be bound by any theory, it is assumed that extractable lithium and especially residual lithium is at least partially drawn to the surface and reacted with Co to Co-Li-containing oxide species.
The present invention is further illustrated by the following working examples.
Percentages are % by weight unless specifically denoted otherwise. RPM: rounds per minute
Manufacture of CAM.1 : Co(OH)2: D50 10.9 pm, span (D90 - D10)/D50 = 2.7 Manufacture of C-CAM.2: Co(OH)2: D50 102.8 pm, span (D90 - D10)/D50 = 12.3
I. Cathode active materials
1.1. Preparation of precursor
A stirred tank reactor was filled with deionized water with ammonium sulfate added (49 g per kg water). The solution was controlled to be 55°C and pH value to be 12 by adding aqueous sodium hydroxide solution. The tank reactor was simultaneously fed with an aqueous transition metal sulfate solution and aqueous sodium hydroxide solution at a flow rate ratio of 1 .8, and a total flow rate resulting in a residence time of 8 hours. The transition metal sulfate solution contained Ni, Co, Mn in a molar ratio of 94 : 3 : 3 and the total transition metal concentration was 1 .65 mol/kg. The aqueous sodium hydroxide solution was a mixture between sodium hydroxide solution (25wt.%) and ammonia solution (25wt.%) in a weight ratio of 6. The pH value 12 was kept by a separate feed of aqueous sodium hydroxide solution. Beginning with the start-up of all feeds, mother liquor was continuously removed. After 27 hours all feed flows were stopped. The mixed transition metal (TM) oxyhydroxide precursor TM-OH.1 was obtained by filtration of resulting suspension, washing with distilled water, drying at 120°C in air, and sieving.
1.2. Preparation of cathode active materials (pristine), step (a)
B-CAM (pristine): The mixed transition metal oxyhydroxide precursor obtained according to 1.1. was mixed with 1.2 mole-% AI(OH)s and 0.3 mole-% ZrC>2, both mole-% referring to the sum of Ni, Co, and Mn in the TM-OH.1 , and LiOH monohydrate with a Li/TM molar ratio of 1.03. The mixture was hearted to 725°C for 8hrs in a forced flow of oxygen to obtain the cathode active material CAM.P.
D50 = 11.1 pm measured using laser diffraction technique in a Mastersizer 3000 instrument from Malvern Instruments. Residual moisture 212 ppm was determined at 230°C.
1.3. Post treatment processes
1.3. 1. Steps (b.1) and (d.1)
A high-shear mixer, Earth Technica FS-10 High Speed Mixer, was charged with 3000 g B-CAM, 58.4 g of the respective Co(OH)2, 2.4 g AI2O3, and 3.7 g TiC>2. Neither water, organic solvent, nor Li source were added. The agitator was set to 570 rpm and the chopper to 3500 rpm for 10 minutes. Then, a mixed powder was obtained. The mixed powder was heat treated at a top temperature 500°C for 5 hours under oxygen flow in a box-type furnace and then cooled naturally. The resultant CAM.1 was obtained when it cooled down to ambient temperature.
SEM/EDX analysis revealed sub-micro sized coating particles of Co compounds (B), which are conformally distributed on CAM.1 particle surface. Higher Co concentration at CAM.1 particle surface in contrast to particle bulk enables to count a coverage ratio of the coated particles vs. the total particles. A SEM/EDX mapping image covering 81 particles was used for counting. In CAM.1 , some 98% of all particles exhibited such features. Synchrotron-sourced X-ray diffractometer (ALBA Synchrotron Light Source, BL04-MSPD, Spain) was used for a high resolution X-ray diffraction. Rietveld refinement using XRD pattern of CAM.1 revealed a LiyiCoO2 (y1 = 0.4) with a spinel structure.
C-CAM.2 was manufactured and analyzed in the same way as CAM.1 but in step c-(b.2) - instead of (b.1), the CO(OH)2 with a span (D90 - D10)/D50 of 12.3 was used. Only 86% of the particles of C-CAM.2 showed the respective coverage.
TEM/EDX analysis on particle cross section of CAM.1 revealed a Co concentration gradient at primary particle surface at both outer and inner region of secondary particle. Furthermore, the said Co gradient is greater for outer surface of primary particle than inner grain boundary between primary particles. The Co gradient is present even at the bulk center region of secondary particle.
II. Testing of Cathode Active Material
11.1. Electrode preparation, general procedure
11.1.1. Cathode preparation
PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a 7.5 wt.% solution. For electrode preparation, binder solution (3 wt.%), graphite (SFG6L, 2 wt.%), and carbon black (Super C65, 1 wt.%) were suspended in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp., Japan), either inventive CAM.1 or comparative cathode active material C-CAM or base material B-CAM (94 wt.%) was added and the resulting suspension was mixed again to obtain a lump-free slurry. The solid content of the slurry was adjusted to 65%. The slurry was coated onto Al foil using a rol l-to-rol I coater. Prior to use, all electrodes were calendared. The thickness of cathode material was 70pm, corresponding to 15 mg/cm2. All electrodes were dried at 105°C for 7 hours before battery assembly.
11.2. Electrolyte preparation
A base electrolyte was prepared by mixing 12.7 wt.% LiPF6, 26.2 wt.% ethylene carbonate (EC), and 61.1 wt.% ethyl methyl carbonate (EMC) (EL base 1), based on the total weight of EL base
I .
II.3 Test cell manufacture
11.3.1. Coin-type half cells
Coin-type half cells (20 mm in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under 11.1.1 and lithium metal as working and counter electrode, respectively, were assembled in an Ar-filled glove box. The cathode, anode, and separator were superposed in order of cathode // separator // Li foil to produce a half coin cell. Thereafter, 0.15mL of EL base 1 as described under II.2 were added into the coin cell. III. Evaluation of cell performance
Cell performance was evaluated in coin-type half cells. Coin-type half cells as described under 11.3.1 were tested in a voltage window between 4.3 and 2.7V at room temperature. For the initial cycles, the de-lithiation was conducted in a CC-CV mode, i.e. , a constant current (CC) of 0.05C was applied followed by holding constant voltage (CV) at 4.3V until reaching 0.02C. After 5 minutes resting time, re-lithiation was carried out at a constant current of 0.05C to 2.7V. For the cycling, the current density is C/3. The results were summarized in Table 1.
Table 1 : Coin-type half cell performance
After 500 cycles tested against a graphite anode, CAM.1 exhibited less cracks than C-CAM.2.
General:
Particle cracking is measured as follows:
(1) artificial intelligence (“Al”) is trained to recognize polished cross-section of the particles of cathode active materials, and to ignore sub-surface features of cathode active material particles;
(2) only the exterior perimeter of the cathode active materials particles is traced because it is in contact with electrolyte, ignoring interior voids that should not have access to electrolyte;
(3) the polished cross-sectional area of the cathode active material particles is determined;
(4) exterior perimeter is divided by the polished cross-sectional area (for normalization purpose), and result is used as a quantifiable measure of cracking. That is, the higher the P/A ratio, the more extensive is the cracking of said cathode active material.

Claims

Patent Claims
1. Cathode active material comprising
(A) a base material according to general formula Lii+xTMi.xO2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Zr, Ti, Nb, Ta, and W, and x is in the range of from zero to 0.2, and
(B) crystallites of cobalt compound(s) in which at least some cobalt is in the oxidation state of +III, wherein base material (A) is a polycrystalline material whose secondary particles are composed of primary particles, and crystallites of cobalt compounds (B) being coated on the outer surface of 90 to 99.5% of the secondary particles, and additional cobalt compound^) being located at said primary particles forming a concentration gradient, determined by EDX and SEM/TEM imaging.
2. Cathode active material according to claim 1 wherein TM is a combination of transition metals according to general formula (I)
(NiaCobMnc)i-dMd (I) with a being in the range of from 0.6 to 0.99, b being in the range of from 0.005 to 0.2, c being in the range of from 0.005 to 0.2, and d being in the range of from zero to 0.1 ,
M is selected from Al, Mg, Ti, Zr, Nb, Ta, and W, and a + b + c = 1.
3. Cathode active material according to claim 1 or 2 wherein said crystallites of cobalt compound^) (B) comprise CO3O4, LiyiCoC>2 (0<y1<0.6) with spinel structure, or LiCoO2.
4. Cathode active material according to any of the preceding claims wherein the coating comprises at least one compound of at least one additional element selected from Ti, Zr and Al.
5. Cathode active material according to any of the preceding claims wherein 20 to 45 % of the secondary particles exhibit cracks after 500 cycles of charging/discharging at 4.2 to 3.0 V in full cell with graphite anode, at 45°C.
6. Cathode active material according to any of the preceding claims wherein the crystallites (B) have an average diameter (D50) in the range of from 10 nm to 1 pm but in any case a smaller diameter than base material (A).
7. Process for making a cathode active material according to any of the preceding claims comprising the steps of
(a) providing a material according to general formula Lii+xTMi.xO2 wherein TM is a combination of Ni and at least one of Mn, Co and Al, and, optionally, at least one more metal selected from Mg, Ti, Zr, Nb, Ta, and W, and x is in the range of from zero to 0.2,
(b) contacting said material with an oxide or (oxy)hydroxide of cobalt and, optionally, up to 10 % by vol of water and, optionally, at least one oxide or hydroxide or oxyhydroxide of Ti, Zr, Nb or Al, wherein said oxide or (oxy) hydroxi de of cobalt has an average particle diameter (D50) in the range of from 10 nm to 50 pm and a span of the particle diameter distribution in the range of from 0.5 to 3.5,
(c) optionally, removing water from the mixture obtained in step (b),
(d) calcining the intermediate of step (b) or - if applicable - step (c).
8. Process according to claim 7 wherein step (c) is performed at a temperature in the range of from 350 to 850°C.
9. Process according to claim 7 or 8 wherein step (b) is performed in a mixer selected from plough share mixers and high shear mixers.
10. Process according to any of claims 7 to 9 wherein step (b) is performed by adding an aqueous slurry of an oxide or (oxy) hydroxi de of cobalt and, optionally, of at least one oxide or hydroxide or oxyhydroxide of Ti, Zr or Al to the material provided in step (a), followed by mixing.
11. Process according to any of claims 7 to 10 wherein step (b) is performed in the dry state.
12. Process according to any of claims 7 to 11 wherein step (b) is performed without adding a separate lithium compound other than Lii+xTMi.x02.
13. Process according to any of claims 7 to 12 wherein step (c) is performed by evaporating the water at least partially at a temperature in the range of from 105 to 200°C.
14. Electrode containing (A) at least one cathode active material according to any of claims 1 to 6,
(B) carbon in electrically conductive form and
(C) a binder.
15. Secondary battery containing (1) at least one electrode according to claim 14,
(2) at least one anode, and
(3) an electrolyte.
EP24714515.4A 2023-04-05 2024-04-02 Cathode active materials comprising cobalt, and way of manufacture Pending EP4688665A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP23166688 2023-04-05
PCT/EP2024/058831 WO2024208775A1 (en) 2023-04-05 2024-04-02 Cathode active materials comprising cobalt, and way of manufacture

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US6921609B2 (en) 2001-06-15 2005-07-26 Kureha Chemical Industry Co., Ltd. Gradient cathode material for lithium rechargeable batteries
EP2634148B1 (en) * 2012-03-01 2015-04-01 GS Yuasa International Ltd. Active material for non-aqueous electrolyte secondary battery, method for production of the active material, electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery
KR102314045B1 (en) * 2014-12-18 2021-10-18 삼성에스디아이 주식회사 Composit cathode active material, preparation method thereof, and cathode and lithium battery containing the composite cathode active material
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