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WO2024088810A1 - Cathode active materials in the form of monoliths, a process for their manufacture, and their use - Google Patents

Cathode active materials in the form of monoliths, a process for their manufacture, and their use Download PDF

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Publication number
WO2024088810A1
WO2024088810A1 PCT/EP2023/078676 EP2023078676W WO2024088810A1 WO 2024088810 A1 WO2024088810 A1 WO 2024088810A1 EP 2023078676 W EP2023078676 W EP 2023078676W WO 2024088810 A1 WO2024088810 A1 WO 2024088810A1
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WIPO (PCT)
Prior art keywords
active material
cathode active
nickel
range
water
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PCT/EP2023/078676
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French (fr)
Inventor
Juergen Janek
Raffael RUESS
Davide GOMBOSO
Mark ULHERR
Enrico TREVISANELLO
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BASF SE
Justus Liebig Universitaet Giessen
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BASF SE
Justus Liebig Universitaet Giessen
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Publication of WO2024088810A1 publication Critical patent/WO2024088810A1/en
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention is directed towards a process for the manufacture of a cathode active material in the form of monoliths, said process comprising the following steps:
  • step (c) heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of U2CO3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively,
  • step (d) cooling the melt from step (c) to a temperature below 300°C, thereby obtaining a solid material
  • step (e) washing the solid material obtained from step (d) with water or with a water/Ci-C2-alcohol mixture or a water/acetone mixture.
  • Lithiated transition metal oxides are currently used as electrode active materials for lithium-ion batteries. Extensive research and developmental work have been performed in the past years to improve properties like charge density, specific energy, but also other properties like the reduced cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithium-ion battery. Additional effort has been made to improve manufacturing methods.
  • NCM materials lithiated nickel-cobalt-man- ganese oxide
  • NCA materials lithiated nickel-cobalt-aluminum oxide
  • a so-called precursor is being formed by co-precipitating the transition metals as carbonates, oxides or preferably as (oxy) hydroxi des.
  • Other ways to make a precursor start from the oxides or (oxy)hydrox- ides of the respective metal(s), in a pure form or as a mixture.
  • the precursor is then mixed with a lithium compound such as, but not limited to LiOH, U2O or U2CO3 and calcined (fired) at high temperatures.
  • Lithium compound(s) can be employed as hydrate(s) or in dehydrated form.
  • the calcination - or firing - generally also referred to as thermal treatment or heat treatment of the precursor - is usually carried out at temperatures in the range of from 600 to 1 ,000 °C.
  • thermal treatment is performed in the heating zone of an oven or kiln.
  • cathode active materials suffer from limited energy density, sometimes also referred to as volumetric energy density. This applies particularly to many cathode active materials with a larger particle diameter, for example many nickel-rich cathode active materials.
  • cathode active materials with a bimodal particle size distribution It has been suggested to increase the energy density in an electrode by using cathode active materials with a bimodal particle size distribution. However, especially when the time for charging is only limited, the overall capacity leaves room for improvement. In addition, cathode active materials with a bimodal particle size distribution still have an energy density the leaves room for improvement.
  • inventive proves The inventive process comprises the following steps, hereinafter also referred to as step (a), step (b), step (c), step (d) and step (e) or more briefly as (a), (b), (c), (d) and (e):
  • step (c) heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of Li2CC>3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively,
  • step (d) cooling the melt from step (c) to a temperature below 300°C, thereby obtaining a solid material
  • step (e) washing the solid material obtained from step (d) with water or with a water/Ci-C2-alcohol mixture or a water/acetone mixture. Steps (a) to (e) are performed subsequently. Steps (a) to (e) will be described in more detail below.
  • a particulate electrode active material of the general formula Lii+xTMi. x O2 in particulate form wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.05 ⁇ x ⁇ +0.05, preferably -0.02 ⁇ x ⁇ +0.02.
  • Some metals are ubiquitous such as sodium, calcium or zinc and traces of them virtually present everywhere, but such traces 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 TM. Analogously, traces of sulfate or carbonate that may stem from the precursor manufacture are neglected as well.
  • electrode active material provided in step (a) is comprised of spherical particles, that are particles have a spherical shape.
  • Spherical particles shall include not just those which are exactly spherical but also those particles in which the maximum and minimum diameter of at least 90% (number average) of a representative sample differ by not more than 10%.
  • electrode active material provided in step (a) is comprised of secondary particles that are agglomerates of primary particles.
  • electrode active material provided in step (a) is comprised of spherical secondary particles that are so-called single crystals or monoliths.
  • said primary particles of electrode active material provided in step (a) have an average diameter in the range from 100 to 4000 nm, preferably from 10 to 1000 nm, particularly preferably from 500 to 1000 nm.
  • the average primary particle diameter can, for example, be determined by SEM or TEM.
  • SEM is an abbreviation of scanning electron microscopy
  • TEM is an abbreviation of transmission electron microscopy.
  • electrode active material provided in step (a) has a monomodal particle diameter distribution, for example with an average value (median) D50 in the range of from 2 to 10 pm, preferably 3 to 5 pm. This size refers to the secondary particles.
  • the pressed density of electrode active material provided in step (a) is in the range of from 3.6 to 4.8 g/cm 3 , determined at a pressure of 250 MPa, preferred are 3.80 to 4.80 g/cm 3 .
  • TM corresponds to general formula (I)
  • Lii +x TMi. x O2 may be obtained by calcination of an oxide or oxy(hydroxide of TM with a source of lithium, for example LiOH or U2CO3, preferably LiOH, under an atmosphere of oxygen in one or two steps. In case a two-step calcination is performed, the second calcination is performed at a lower temperature than the first, for example lower by 25 to 75°C.
  • Step (b) includes mixing said electrode active material with a compound selected from LiCI, KCI, CsCI, U2CO3 and combinations of at least two of them, for example LiCI and KCI or LiCI and U2CO3.
  • said compound is U2CO3 and is chloride-free.
  • chloride-free means that the chloride content is less than 100 ppm by weight, determined by inductively coupled plasma (“ICP”) and referring to said U2CO3.
  • electrode active material provided in step (a) is mixed with LiOH and a compound selected from LiCI, KCI, CsCI, and U2CO3 and combinations of at least two of them.
  • the weight ratio of LiOH and compound(s) selected from LiCI, KCI, CsCI, and U2CO3 and combinations of at least two of them may be in the range of from 1 : 1 to 1 : 10, Preferably, the molar amount of compound(s) selected from LiCI, KCI, CsCI, and Li 2 CC>3 exceeds the amount of LiOH.
  • the weight ratio of electrode active material from step (a) and compound(s) selected from LiCI, KCI, CsCI, and U2CO3, alone or together with LiOH, and combinations of at least two of them in step (b) is in the range of from 6:1 to 1 :1 , preferred are 3.3:1 to 1 :1. In embodiments wherein higher amounts of especially U2CO3, alone or together with LiOH, are used, this may lead to deliquescing of the mixture which should be avoided.
  • Compound selected from LiCI, KCI, CsCI, and U2CO3 may have an average particle diameter (D50) in the range of from 0.1 to 20 pm, preferably 0.1 to 1 pm.
  • Suitable vessels for mixing electrode active material provided in step (a) and compound(s) selected from LiCI, KCI, CsCI, U2CO3 and combinations are paddle mixers, tumble mixers, free fall mixers, and high sheer mixers. On laboratory scale, when amounts of 5 g or less of electrode material are mixed, mortars with pestle or low energy ball mills are suitable as well.
  • the duration of step (b) is in the range of from one minute to 2 hours.
  • Step (b) may be performed at a temperature of from -5°C to 100°C. It is observed that in certain vessel types, the mixture becomes warm when mixed. It is preferred to perform step (b) without external heating.
  • a mixture is obtained from step (b).
  • Step (c) includes heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of U2CO3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively.
  • the mixture obtained in step (b) contains a combination of at least two of LiCI, KCI, CsCI, or U2CO3, a temperature is selected in step (c) that corresponds to the higher melting point.
  • U2CO3 is the sole compound added in step (b).
  • the melting point is 720°C, and a temperature of from 720 to 770°C is useful, preferably 720 to 750°C.
  • a combination of at least two of LiCI, KCI, CsCI, or U2CO3, alone or together with LiOH is present that forms a eutectic mixture, for example a eutectic mixture of LiOH and U2CO3.
  • the temperature in step (c) is selected in a way that as a lower limit, the melting point of said eutectic mixture is selected.
  • a temperature of up to 50 °C above the melting point is selected.
  • step (c) is performed in a roller hearth kiln or in a pusher kiln.
  • crucibles, saggars or pans are applied.
  • muffle ovens and tube ovens are suitable as well.
  • step (c) is performed under an atmosphere of pure oxygen or oxygen-enriched air, for example with an oxygen : air ratio (by volume) of 4:1 or higher.
  • step (c) has a duration in the range of from one to 60 hours, preferred are 12 to 24 hours.
  • step (c) is performed under an atmosphere free from moisture and CO2.
  • free from moisture and CO 2 shall mean that the moisture and CO2 content is 0.01 % by volume or less.
  • the carbon dioxide content may be detected by IR spectroscopy.
  • humidity is not controlled during step (c).
  • the mixture obtained in step (b) is converted into a pellet before heat treatment according to step (c).
  • Such pellets may have the following dimensions: Preferably, such pellets are tablet shaped, for example with a circle as base and a height in the range of from 1 to 5 mm. Said circle may have a diameter in the range of from 5 to 20 mm.
  • Step (d) includes cooling the melt from step (c) to a temperature below 300°C, preferably 20 to 100°C, thereby obtaining a solid material. Step (d) is preferably performed by natural cooling. A solid material is obtained from step (d).
  • a vessel such as a crucible, saggar or pan is removed from the apparatus in which step (c) is performed and then exposed to ambient temperature.
  • Step (d) is preferably performed under an atmosphere that is free from moisture and carbon dioxide.
  • the pellets are crushed or milled after step (d).
  • the duration of step (d) is in the range of from one to ten hours.
  • step (e) the solid material obtained from step (d) is washed with water or with a water/Ci-C2- alcohol mixture or with a water/acetone mixture, water being preferred.
  • Said water/Ci-C2-alcohol mixture may contain water and methanol or ethanol in a ratio of 10:1 to 1 :10 by volume.
  • Said water/acetone mixture may contain water and acetone in a ratio of 10:1 to 1 :10 by volume.
  • Ternary mixtures of water, Ci-C2-alcohol and acetone are feasible as well.
  • Step (e) serves to remove compound(s) selected from LiOH, LiCI, KCI, CsCI and U2CO3.
  • step (e) is performed at a temperature in the range of from -5 to +20°C, preferably from -5 to +5°C. In embodiments wherein temperatures below zero °C are desired, the addition of methanol or ethanol or acetone is required.
  • the volume ratio of solid obtained from step (d) and water or with a water/Ci-C2-alcohol mixture, as the case may be, is in the range of from 1 to 50 ml per g of cathode active material.
  • step (b) is carried out with U2CO3
  • the preferred range is 1 to 5 ml water or a water/Ci-C2-alcohol mixture per g of cathode active material.
  • Step (e) may be supported by mixing operations such as shaking or preferably stirring.
  • step (e) water is used that is devoid of water hardness, for example by distillation of by passing it through an ion exchanger.
  • Step (e) may be carried out once or up to ten times, hereinafter also referred to as sub-steps.
  • step (e) The higher the number of repetitions of step (e), the better the removal of compound(s) selected from LiCI, KCI, CsCI and Li2CO3. It is possible to use the same washing medium in all sub-steps or to use different washing media, for example pure water in one to three first sub-step(s) and a water/ethanol mixture in a second sub-step and a water/acetone mixture in a third sub-step, or pure water in one to three first sub-step(s), a water/ethanol mixture in one to three second substeps and water/acetone in a third sub-step.
  • the higher the number of repetitions of step (e) the higher is the impact on the surface of the cathode active material.
  • the duration of sub-steps may be in the range of from 30 seconds to 15 minutes, preferred are 60 to 120 seconds.
  • Step (e) includes removal of the water after washing, for example by decantation, filtration, or by means of a centrifuge. A solid residue is produced. More water may be removed by washing with pure methanol, ethanol or acetone or a combination of at least two of the foregoing.
  • a subsequent step (f) is added that includes a thermal treatment at a temperature in the range of from 500 to 725°C.
  • step (f) is performed in a rotary kiln, in a roller hearth kiln or in a pusher kiln.
  • the thermal treatment of step (f) has a duration in the range of from one hour to six hours. The time required for reaching the target temperature is neglected in this context.
  • Step (f) may be carried out under an atmosphere of air, oxygen-enriched air, synthetic air (nitrogen : oxygen of 4:1 by volume) or pure oxygen.
  • step (f) is carried out under pure oxygen or oxygen-enriched air, for example oxygen : air in the range of from 10:1 to 2:1 by volume.
  • step (f) is performed under an atmosphere that is free from moisture and CO2.
  • the resultant cathode active material is cooled to ambient temperature. It is advantageous to then de-agglomerate it, for example by crushing or milling, and to remove lumps by sieving.
  • cathode active materials are obtained that comprise nonagglomerated octahedral crystals and that meet the objectives discussed at the outset. It is in the form of monoliths, preferably in the form of octahedral crystals (“single crystals”).
  • a further aspect of the present invention refers to cathode active materials, hereinafter also referred to as inventive cathode active materials.
  • inventive cathode active materials may be obtained according to the inventive process. They are described in more detail below.
  • Inventive cathode active materials contain non-agglomerated octahedral crystals of the general formula Lii +x TMi-xO2 wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.02 ⁇ x ⁇ +0.02.
  • inventive cathode active materials comprise up to 2 mol-% particulate U2CO3. Such particles may have a diameter of up to 2 pm.
  • At least 50% of the particles of inventive cathode active materials have an octahedral shape, for example 50 to 100%, preferably 55 to 95%. The percentage may be determined, e.g., by evaluation of SEM images.
  • inventive cathode active materials may have a broad particle size distribution.
  • the particle size distribution may be determined by sieving methods, by SEM image analysis or by dynamic light scattering and be characterized by the span, (D90)-(D10), divided by (D50).
  • inventive cathode active material have a span in the range of from 1 .0 to 1 .4.
  • inventive cathode active material has a mono- modal particle diameter distribution, for example with an average value (median) D50 in the range of from 2 to 8 pm, preferably 3 to 5 pm. This size refers to the secondary particles.
  • the pressed density of inventive cathode active material is in the range of from 3.6 to 4.8 g/cm 3 , determined at a pressure of 250 MPa, preferred are 3.80 to 4.80 g/cm 3 .
  • TM corresponds to general formula (I)
  • TM is nickel
  • Inventive cathode active materials are excellently suited for making cathodes for lithium-ion batteries and especially for all-solid state lithium-ion batteries. They are particularly well suited in combination with a polycrystalline cathode active material with an average (median) diameter in the range of from 9 to 16 pm, for example in a volume (or weight) ratio of inventive cathode active material to polycrystalline cathode active material in the range of from 1 :2 to 1 :10, preferably 3:7 to 1 :5. Such blends have a high volumetric energy density.
  • the element composition of said polycrystalline cathode active material may be the same as the element composition of inventive cathode active material or be different.
  • said polycrystalline cathode active material may have a general formula Lii +x iTM’i-xiO2 wherein TM’ is a combination of nickel and at least one of Co and Mn and, optionally, at least one dopant selected from Al, Mg, W, Mo, Nb, Ta, Zr and Ti, wherein the percentage of nickel is at least 80 mol-%, referring to the sum of Ni, Co and Mn if present, preferably at least 90 mol-%.
  • TM’ is nickel or corresponds to general formula (I a)
  • Polycrystalline cathode active materials is comprised of secondary particles that are agglomerates of primary particles.
  • polycrystalline cathode active material is comprised of spherical secondary particles that are agglomerates of platelet primary particles.
  • the pressed density of such blends is in the range of from 3.6 to 4.8 g/cm 3 , determined at a pressure of 250 MPa, preferred are 3.80 to 4.80 g/cm 3 .
  • a further aspect of the present invention refers to electrodes comprising at least one electrode active material according to the present invention. They are particularly useful for lithium-ion batteries, with a liquid non-aqueous electrolyte or with a solid electrolyte. Lithium-ion batteries comprising at least one electrode according to the present invention exhibit a good discharge behavior. Electrodes comprising at least one electrode active material according to the present invention are hereinafter also referred to as inventive cathodes or cathodes according to the present invention. Specifically, inventive cathodes contain
  • At least one electrode active material selected from inventive cathode active material or preferably a blend from inventive cathode active material and a polycrystalline cathode active material
  • binder also referred to as binders or binders (C)
  • binders also referred to as binders or binders (C)
  • inventive cathodes contain
  • electrode active material selected from inventive cathode active material or preferably a blend from inventive cathode active material and a polycrystalline cathode active material
  • 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, and from combinations of at least two of the foregoing.
  • 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-ethyl
  • polypropylene is not only understood to mean homo-pol- ypropylene, 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-diphe- nylethylene and a-methylstyrene.
  • Another preferred binder (C) is polybutadiene.
  • Suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, polyimides and polyvinyl alcohol.
  • binder (C) 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 (C) may be selected from cross-linked or non-cross-linked (co)polymers.
  • binder (C) 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 (C) 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 electrode active material. In other embodiments, inventive cathodes may comprise 0.1 up to less than 1% by weight of binder(s).
  • Inventive cathodes used in lithium-ion batteries with liquid electrolytes usually contain a binder.
  • Inventive cathodes used in so-called all-solid-state lithium-ion batteries - or “solid-state batteries” - usually contain some solid electrolyte and, optionally, a binder.
  • inventive cathodes comprise a solid-state electrolyte.
  • Such solid-state is solid at ambient temperature.
  • such solid electrolyte has a lithium-ion conductivity at 25 °C of > 0.1 mS/cm, preferably in the range of from 0.1 to 30 mS/cm, measurable by, e.g., impedance spectroscopy.
  • such solid electrolyte comprises U3PS4, P-U3PS4 or U3I nCI 6 , yet more preferably argyrodite-type LiePSsCI.
  • solid electrolyte is selected from the group consisting of U2S-P2S5, Li2S-P2Ss-Lil, Li2S-P2Ss-Li2O, Li2S-P2Ss-Li2O-Lil, Li2S-SiS2-P2Ss-Lil, U2S-P2S5- Z m Sn wherein m and n are positive numbers and Z is a member selected from the group consisting of germanium, gallium and zinc, Li 2 S-SiS2-Li 3 PO4, Li 2 S-SiS2-Li y PO z , wherein y and z are positive numbers, U7P3S11, U3PS4, U11S2PS12, U7P2S8I, and Li7-r-2sPS6-r- s X r wherein X is chlorine, bromine or iodine, and the variables are defined as follows:
  • inventive cathodes for solid-state batteries contain solid electrolytes in the range of from 5 to 40% by weight.
  • inventive cathodes for solid-state batteries contain in the range of from 5 to 40% by weight solid electrolyte and in the range of from 0.5 to 3% by weight of carbon (B).
  • a further aspect of the present invention is a battery, containing at least one cathode comprising inventive electrode 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, metallic lithium, silicon, indium 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.
  • polyalkylene glycols examples include poly-Ci-C4-al- kylene 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-di- methoxyethane, 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.
  • 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.
  • R 1 is fluorine and 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 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 , LiCIC>4, with particular preference being given to LiPF 6 and LiN(CF 3 SO2)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. 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.
  • solid electrolyte may serve as separator.
  • 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 provides for the use of batteries according to the invention in appliances, in particular in mobile appliances.
  • mobile appliances are vehicles, for example automobiles, bicycles, aircrafts 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.
  • Average particle diameters were determined by SEM image analysis. Percentages are % by weight unless specifically noted otherwise.
  • LiOH H 2 O was purchased from Sigma Aldrich.
  • U2CO3 was purchased from Alfa Aesar.
  • NiO (as precursor) was purchased from Alfa Aesar.
  • step (e) ultra-pure water purified in accordance with Milli Q® laboratory water systems from Merck was used.
  • base electrode active materials were manufactured in a box furnace, type: tube furnace, model Nabertherm RT 50-250/13, with an alumina tube.
  • Step (a.1): Manufacture of a base material, B-CAM.1 , TM Ni
  • NiO was purchased as a powder (325 mesh) from Alfa Aesar with an average primary particle size of 1 pm.
  • nickel oxide powder was mixed with LiOH H 2 O at a molar ratio of Li : Ni of 1.1 :1 and calcined in a flow of pure oxygen (100 cm 3 /min) at 825 °C for 6 h, followed by annealing at 680 °C for 6 h. The heating rate was 100 K/h.
  • the black brick-like material was ground into a fine powder for 15 min.
  • Particulate lithium nickel oxide, B-CAM.1 was obtained and sieved using a mash size of 45 pm. (D50) of B-CAM.1 : 7.0 pm.
  • nickel oxide powder was mixed with LiOH H 2 O at a molar ratio of Li : Ni of 1.1 :1 and calcined in a flow of pure oxygen (100 cm 3 /min) at 780 °C for 6 h, followed by annealing at 680 °C for 6 h. The heating rate was 100 K/h.
  • the black brick-like material was ground into a fine powder for 15 min.
  • Particulate lithium nickel oxide, B-CAM.2 was obtained and sieved using a mash size of 45 pm. (D50) of B-CAM.1 : 3.0 pm.
  • Step (c.1) The above pellets were placed into alumina crucibles and heated to 750°C for 40 h and 20 h at 680 °C. The melting point of Li 2 CO3 is 720°C.
  • Step (d.1) They were then cooled to ambient temperature by natural cooling, rate about 100 K/h. The resultant solid mass was crushed manually in a mortar to obtain a powder.
  • Step (e.1) Sub-step 1 : An amount of 1 g powder from step (d.1) was immersed into 30 ml ice- cold (0 °C) ultrapure water and stirred vigorously for a minute. The slurry was allowed to settle. Supernatant water was removed by decantation, then the solid was recovered by means of a centrifuge.
  • Sub-step 1 was repeated with water twice. Water was then removed from the solid by washing with ethanol and with acetone.
  • Step (f.1) The powder resulting from step (e.1) was then heated to 700°C for 3 hours under conditions otherwise like in step (a.1). After natural cooling to ambient temperature, CAM.1 was ground in a mortar for 3 minutes. CAM.1 was obtained.
  • Figure 1 shows that both CAM.1 and CAM.2 consist of non-agglomerated, octahedral singlecrystalline particles.
  • the particle size depended on the base materials B-CAM.1 or B-CAM.2 and were D50 » 7 pm (CAM.1) and D50 » 3 pm (CAM.2), respectively.
  • the XRD patterns for CAM.1 and CAM.2 are shown in Figure 2. It is thereby shown that Lii +x Nii. x O2 with x ⁇ 0.02 was obtained.
  • the cathode slurries necessary for cathode preparation were prepared by mixing a 5 wt% binder solution of polyvinylidene difluoride (PVDF, Solef 5130, Solvay) in /V-methyl-2-pyrroli- done (NMP, > 99.5%, Merck KGaA) with 5 wt% conductive carbon black (Super-P, TIMCAL Ltd.) and NMP in a planetary centrifugal mixer (DAC 150.1 FVZ-K) three times for 5 min at 2000 rpm. Afterwards, the either B-CAM.1 or CAM.1 was added to the slurry in an open mixing cup was used.
  • PVDF polyvinylidene difluoride
  • NMP > 99.5%, Merck KGaA
  • Super-P TIMCAL Ltd.
  • DAC 150.1 FVZ-K planetary centrifugal mixer
  • the mixture was then stirred again for 5 min at 2000 rpm, yielding a homogenous deep black slurry.
  • a motorized film applicator (MTI Corporation, MSK-AFA-II-VC-FH Tape Casting Coater )
  • the slurry was then immediately coated on 0.03 mm thick aluminum foil using a blade film applicator with a slit height of 60 pm for B-CAM.1 or CAM.1 to obtain areal loadings of 3 mg C AM cm- 2 .
  • the obtained tapes were dried at 120 °C in vacuo for 12 hours and pressed at 100 MPa.
  • the cathode composite consisted of 63 wt% inventive cathode active material, 36 wt% LialnCle (NEI) and 1 wt% carbon fibers (Aldrich), which were mixed by hand grinding for 15 min.
  • the cathode powder was pelletized at 400 MPa and the areal loading was ⁇ 4 mgcAM cnr 2 .
  • CR2032 lithium-ion battery cells (“LIB”) were assembled in an argon-filled glovebox (H2O ⁇ 0.5 ppm and O2 ⁇ 0.5 ppm) and comprised a cathode (12 mm diameter) according to III.1 , a GF/D glass microfiber or Celgard 2500 separator (16 mm diameter; GE Healthcare Life Science, Whatman), a lithium metal anode (14 mm diameter), and 75 pl of electrolyte, consisting of 1.0 M LiPF 6 in 3:7 EC: EMC (ethyl methyl ketone) by weight.
  • EMC ethyl methyl ketone
  • the cathode composite (active material loading ⁇ 4 mg cm -2 ) was loaded onto a two-sided pelletized separator consisting of 50 mg Li 3 l nCh (towards the cathode side) and 30 mg Li 6 PSsCI (NEI) (towards the anode side).
  • Cathode and separator were circle-shaped with a diameter of 10 mm.
  • the cathode and separator were consolidated by pressing with 400 MPa.
  • the anode was prepared by sequentially placing an indium foil (100 pm thickness, 9 mm diameter, ChemPur) and a lithium foil (100 pm thickness, 6 mm diameter, China Energy Lithium) on top of the separator. The cell was then tightly sealed, taken out of the glovebox and pressurized with 120 MPa which was maintained throughout the experiments.
  • LiB Test protocol At least two cells were successfully cycled at 45°C.

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Abstract

Process for the manufacture of a cathode active material in the form of monoliths, said process comprising the following steps: (a) providing an electrode active material of the general formula Li1+xTM1-xO2 in particulate form wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.05 ≤ x ≤+0.05, (b) mixing said electrode active material with a compound selected from LiCl, KCl, CsCl, Li2CO3 and combinations of at least two of them, (c) heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of Li2CO3 or up to 50°C higher than the melting point of LiCl, KCl, CsCl, or Li2CO3, respectively, (d) cooling the melt from step (c) to ambient temperature, thereby obtaining a solid material, (e) washing the solid material obtained from step (d) with water or with a water/C1-C2-alcohol mixture or a water/acetone mixture.

Description

Cathode active materials in the form of monoliths, a process for their manufacture, and their use
The present invention is directed towards a process for the manufacture of a cathode active material in the form of monoliths, said process comprising the following steps:
(a) providing an electrode active material of the general formula Lii+xTMi.xO2 in particulate form wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.05 < x <+0.05,
(b) mixing said electrode active material with a compound selected from LiCI, KCI, CsCI, IJ2CO3 and combinations of at least two of them,
(c) heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of U2CO3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively,
(d) cooling the melt from step (c) to a temperature below 300°C, thereby obtaining a solid material,
(e) washing the solid material obtained from step (d) with water or with a water/Ci-C2-alcohol mixture or a water/acetone mixture.
Lithiated transition metal oxides are currently used as electrode active materials for lithium-ion batteries. Extensive research and developmental work have been performed in the past years to improve properties like charge density, specific energy, but also other properties like the reduced cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithium-ion battery. Additional effort has been made to improve manufacturing methods.
Many electrode active materials discussed today are of the type of lithiated nickel-cobalt-man- ganese oxide (“NCM materials”) or lithiated nickel-cobalt-aluminum oxide (“NCA materials”).
In a typical process for making cathode materials for lithium-ion batteries, first a so-called precursor is being formed by co-precipitating the transition metals as carbonates, oxides or preferably as (oxy) hydroxi des. Other ways to make a precursor start from the oxides or (oxy)hydrox- ides of the respective metal(s), in a pure form or as a mixture. The precursor is then mixed with a lithium compound such as, but not limited to LiOH, U2O or U2CO3 and calcined (fired) at high temperatures. Lithium compound(s) can be employed as hydrate(s) or in dehydrated form. The calcination - or firing - generally also referred to as thermal treatment or heat treatment of the precursor - is usually carried out at temperatures in the range of from 600 to 1 ,000 °C. In cases hydroxides or carbonates are used as precursors a removal of water or carbon dioxide occurs first and is followed by the lithiation reaction. The thermal treatment is performed in the heating zone of an oven or kiln.
Still, many cathode active materials suffer from limited energy density, sometimes also referred to as volumetric energy density. This applies particularly to many cathode active materials with a larger particle diameter, for example many nickel-rich cathode active materials.
It has been suggested to increase the energy density in an electrode by using cathode active materials with a bimodal particle size distribution. However, especially when the time for charging is only limited, the overall capacity leaves room for improvement. In addition, cathode active materials with a bimodal particle size distribution still have an energy density the leaves room for improvement.
It was therefore an objective of the present invention to provide electrochemical cells with high energy density. It was further an objective to provide such cathode active materials, and it was an objective to provide a method to make such cathode active materials with high energy density.
Accordingly, the process as defined at the outset has been found, hereinafter also referred to as inventive proves. The inventive process comprises the following steps, hereinafter also referred to as step (a), step (b), step (c), step (d) and step (e) or more briefly as (a), (b), (c), (d) and (e):
(a) providing an electrode active material of the general formula Lii+xTMi.xO2 in particulate form wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.05 < x <+0.05,
(b) mixing said electrode active material with a compound selected from LiCI, KCI, CsCI, □2 03 and combinations of at least two of them,
(c) heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of Li2CC>3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively,
(d) cooling the melt from step (c) to a temperature below 300°C, thereby obtaining a solid material,
(e) washing the solid material obtained from step (d) with water or with a water/Ci-C2-alcohol mixture or a water/acetone mixture. Steps (a) to (e) are performed subsequently. Steps (a) to (e) will be described in more detail below.
In step (a), a particulate electrode active material of the general formula Lii+xTMi.xO2 in particulate form is provided wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.05 < x <+0.05, preferably -0.02 < x <+0.02.
Some metals are ubiquitous such as sodium, calcium or zinc and traces of them virtually present everywhere, but such traces 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 TM. Analogously, traces of sulfate or carbonate that may stem from the precursor manufacture are neglected as well.
In one embodiment of the present invention, electrode active material provided in step (a) is comprised of spherical particles, that are particles have a spherical shape. Spherical particles shall include not just those which are exactly spherical but also those particles in which the maximum and minimum diameter of at least 90% (number average) of a representative sample differ by not more than 10%.
In one embodiment of the present invention, electrode active material provided in step (a) is comprised of secondary particles that are agglomerates of primary particles. Preferably, electrode active material provided in step (a) is comprised of spherical secondary particles that are so-called single crystals or monoliths.
In one embodiment of the present invention, said primary particles of electrode active material provided in step (a) have an average diameter in the range from 100 to 4000 nm, preferably from 10 to 1000 nm, particularly preferably from 500 to 1000 nm. The average primary particle diameter can, for example, be determined by SEM or TEM. SEM is an abbreviation of scanning electron microscopy, TEM is an abbreviation of transmission electron microscopy. In one embodiment of the present invention, electrode active material provided in step (a) has a monomodal particle diameter distribution, for example with an average value (median) D50 in the range of from 2 to 10 pm, preferably 3 to 5 pm. This size refers to the secondary particles.
In one embodiment of the present invention, the pressed density of electrode active material provided in step (a) is in the range of from 3.6 to 4.8 g/cm3, determined at a pressure of 250 MPa, preferred are 3.80 to 4.80 g/cm3.
In one embodiment of the present invention, TM corresponds to general formula (I)
(NiaCObMnc)i-dM1d (I) with a being in the range of from 0.95 to 0.99, preferably from 0.97 to 0.99, b being zero or in the range of from 0.01 to 0.05, c being in the range of from zero to 0.02, and d being in the range of from zero to 0.04, preferably from 0.01 to 0.02,
M1 is at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, preferably at least one of Al, Mg, Ti, Mo, W and Zr, and more preferably exactly one of Al, Mg, Ti, Mo, W and Zr, a + b + c = 1 , b + c > zero.
Lii+xTMi.xO2 may be obtained by calcination of an oxide or oxy(hydroxide of TM with a source of lithium, for example LiOH or U2CO3, preferably LiOH, under an atmosphere of oxygen in one or two steps. In case a two-step calcination is performed, the second calcination is performed at a lower temperature than the first, for example lower by 25 to 75°C.
Step (b) includes mixing said electrode active material with a compound selected from LiCI, KCI, CsCI, U2CO3 and combinations of at least two of them, for example LiCI and KCI or LiCI and U2CO3. Preferably, said compound is U2CO3 and is chloride-free. In this context, the term “chloride-free” means that the chloride content is less than 100 ppm by weight, determined by inductively coupled plasma (“ICP”) and referring to said U2CO3.
In one embodiment of step (b), electrode active material provided in step (a) is mixed with LiOH and a compound selected from LiCI, KCI, CsCI, and U2CO3 and combinations of at least two of them. The weight ratio of LiOH and compound(s) selected from LiCI, KCI, CsCI, and U2CO3 and combinations of at least two of them may be in the range of from 1 : 1 to 1 : 10, Preferably, the molar amount of compound(s) selected from LiCI, KCI, CsCI, and Li2CC>3 exceeds the amount of LiOH.
In one embodiment of the present invention, the weight ratio of electrode active material from step (a) and compound(s) selected from LiCI, KCI, CsCI, and U2CO3, alone or together with LiOH, and combinations of at least two of them in step (b) is in the range of from 6:1 to 1 :1 , preferred are 3.3:1 to 1 :1. In embodiments wherein higher amounts of especially U2CO3, alone or together with LiOH, are used, this may lead to deliquescing of the mixture which should be avoided.
Compound selected from LiCI, KCI, CsCI, and U2CO3 may have an average particle diameter (D50) in the range of from 0.1 to 20 pm, preferably 0.1 to 1 pm.
Suitable vessels for mixing electrode active material provided in step (a) and compound(s) selected from LiCI, KCI, CsCI, U2CO3 and combinations are paddle mixers, tumble mixers, free fall mixers, and high sheer mixers. On laboratory scale, when amounts of 5 g or less of electrode material are mixed, mortars with pestle or low energy ball mills are suitable as well.
In one embodiment of the present invention, the duration of step (b) is in the range of from one minute to 2 hours.
Step (b) may be performed at a temperature of from -5°C to 100°C. It is observed that in certain vessel types, the mixture becomes warm when mixed. It is preferred to perform step (b) without external heating.
A mixture is obtained from step (b).
Step (c) includes heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of U2CO3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively. In cases the mixture obtained in step (b) contains a combination of at least two of LiCI, KCI, CsCI, or U2CO3, a temperature is selected in step (c) that corresponds to the higher melting point. In one embodiment of the present invention, U2CO3 is the sole compound added in step (b). The melting point is 720°C, and a temperature of from 720 to 770°C is useful, preferably 720 to 750°C.
In one embodiment of the present invention, a combination of at least two of LiCI, KCI, CsCI, or U2CO3, alone or together with LiOH, is present that forms a eutectic mixture, for example a eutectic mixture of LiOH and U2CO3. In such embodiments, the temperature in step (c) is selected in a way that as a lower limit, the melting point of said eutectic mixture is selected. As upper limit, a temperature of up to 50 °C above the melting point is selected.
In a preferred embodiment of the present invention, step (c) is performed in a roller hearth kiln or in a pusher kiln. For roller hearth kilns or pusher kilns, crucibles, saggars or pans are applied. In small scale experiments, for example with 100 g or less, muffle ovens and tube ovens are suitable as well.
In one embodiment of the present invention, step (c) is performed under an atmosphere of pure oxygen or oxygen-enriched air, for example with an oxygen : air ratio (by volume) of 4:1 or higher.
In one embodiment of the present invention, step (c) has a duration in the range of from one to 60 hours, preferred are 12 to 24 hours.
Preferably, step (c) is performed under an atmosphere free from moisture and CO2. In the context of the present invention, “free from moisture and CO2“ shall mean that the moisture and CO2 content is 0.01 % by volume or less. The carbon dioxide content may be detected by IR spectroscopy. In other embodiments, humidity is not controlled during step (c).
From step (c), a melt is obtained.
In one embodiment of the present invention, the mixture obtained in step (b) is converted into a pellet before heat treatment according to step (c). Such pellets may have the following dimensions: Preferably, such pellets are tablet shaped, for example with a circle as base and a height in the range of from 1 to 5 mm. Said circle may have a diameter in the range of from 5 to 20 mm. Step (d) includes cooling the melt from step (c) to a temperature below 300°C, preferably 20 to 100°C, thereby obtaining a solid material. Step (d) is preferably performed by natural cooling. A solid material is obtained from step (d).
In one embodiment, a vessel such as a crucible, saggar or pan is removed from the apparatus in which step (c) is performed and then exposed to ambient temperature.
Step (d) is preferably performed under an atmosphere that is free from moisture and carbon dioxide.
In embodiments where the mixture from step (b) is converted into pellets, the pellets are crushed or milled after step (d).
In one embodiment of the present invention, the duration of step (d) is in the range of from one to ten hours.
In step (e), the solid material obtained from step (d) is washed with water or with a water/Ci-C2- alcohol mixture or with a water/acetone mixture, water being preferred. Said water/Ci-C2-alcohol mixture may contain water and methanol or ethanol in a ratio of 10:1 to 1 :10 by volume. Said water/acetone mixture may contain water and acetone in a ratio of 10:1 to 1 :10 by volume. Ternary mixtures of water, Ci-C2-alcohol and acetone are feasible as well. Step (e) serves to remove compound(s) selected from LiOH, LiCI, KCI, CsCI and U2CO3. Although a complete removal of remove compound(s) selected from LiOH, LiCI, KCI, CsCI and U2CO3 is desirable, it is observed that a residual 0.01 to 2.0 mol-% of such compound(s) is left in the resultant cathode active material, more easily 0.1 to 2 mol-%.
In one embodiment of the present invention, step (e) is performed at a temperature in the range of from -5 to +20°C, preferably from -5 to +5°C. In embodiments wherein temperatures below zero °C are desired, the addition of methanol or ethanol or acetone is required.
In one embodiment of the present invention, the volume ratio of solid obtained from step (d) and water or with a water/Ci-C2-alcohol mixture, as the case may be, is in the range of from 1 to 50 ml per g of cathode active material. In case step (b) is carried out with U2CO3, preferred are 1 to 30 ml water per g of cathode active material. In case of LiCI, KCI, CsCI, the preferred range is 1 to 5 ml water or a water/Ci-C2-alcohol mixture per g of cathode active material. Step (e) may be supported by mixing operations such as shaking or preferably stirring.
Preferably, in step (e) water is used that is devoid of water hardness, for example by distillation of by passing it through an ion exchanger.
Step (e) may be carried out once or up to ten times, hereinafter also referred to as sub-steps.
The higher the number of repetitions of step (e), the better the removal of compound(s) selected from LiCI, KCI, CsCI and Li2CO3. It is possible to use the same washing medium in all sub-steps or to use different washing media, for example pure water in one to three first sub-step(s) and a water/ethanol mixture in a second sub-step and a water/acetone mixture in a third sub-step, or pure water in one to three first sub-step(s), a water/ethanol mixture in one to three second substeps and water/acetone in a third sub-step. On the downside, the higher the number of repetitions of step (e), the higher is the impact on the surface of the cathode active material.
The duration of sub-steps may be in the range of from 30 seconds to 15 minutes, preferred are 60 to 120 seconds.
Step (e) includes removal of the water after washing, for example by decantation, filtration, or by means of a centrifuge. A solid residue is produced. More water may be removed by washing with pure methanol, ethanol or acetone or a combination of at least two of the foregoing.
In one embodiment of the present invention, a subsequent step (f) is added that includes a thermal treatment at a temperature in the range of from 500 to 725°C. In one embodiment of the present invention, step (f) is performed in a rotary kiln, in a roller hearth kiln or in a pusher kiln.
In one embodiment of the present invention, the thermal treatment of step (f) has a duration in the range of from one hour to six hours. The time required for reaching the target temperature is neglected in this context.
Step (f) may be carried out under an atmosphere of air, oxygen-enriched air, synthetic air (nitrogen : oxygen of 4:1 by volume) or pure oxygen. In a preferred embodiment, step (f) is carried out under pure oxygen or oxygen-enriched air, for example oxygen : air in the range of from 10:1 to 2:1 by volume. Preferably, step (f) is performed under an atmosphere that is free from moisture and CO2. After completion of the heat treatment, the resultant cathode active material is cooled to ambient temperature. It is advantageous to then de-agglomerate it, for example by crushing or milling, and to remove lumps by sieving.
By performing the inventive process, cathode active materials are obtained that comprise nonagglomerated octahedral crystals and that meet the objectives discussed at the outset. It is in the form of monoliths, preferably in the form of octahedral crystals (“single crystals”).
A further aspect of the present invention refers to cathode active materials, hereinafter also referred to as inventive cathode active materials. Inventive cathode active materials may be obtained according to the inventive process. They are described in more detail below.
Inventive cathode active materials contain non-agglomerated octahedral crystals of the general formula Lii+xTMi-xO2 wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.02 < x <+0.02.
In one embodiment of the present invention, inventive cathode active materials comprise up to 2 mol-% particulate U2CO3. Such particles may have a diameter of up to 2 pm.
In one embodiment of the present invention, at least 50% of the particles of inventive cathode active materials have an octahedral shape, for example 50 to 100%, preferably 55 to 95%. The percentage may be determined, e.g., by evaluation of SEM images.
Inventive cathode active materials may have a broad particle size distribution. The particle size distribution may be determined by sieving methods, by SEM image analysis or by dynamic light scattering and be characterized by the span, (D90)-(D10), divided by (D50). In one embodiment of the present invention, inventive cathode active material have a span in the range of from 1 .0 to 1 .4.
In one embodiment of the present invention, inventive cathode active material has a mono- modal particle diameter distribution, for example with an average value (median) D50 in the range of from 2 to 8 pm, preferably 3 to 5 pm. This size refers to the secondary particles. In one embodiment of the present invention, the pressed density of inventive cathode active material is in the range of from 3.6 to 4.8 g/cm3, determined at a pressure of 250 MPa, preferred are 3.80 to 4.80 g/cm3.
In one embodiment of the present invention, TM corresponds to general formula (I)
(NiaCObMnc)i-dM1d (I) with a being in the range of from 0.95 to 0.99, preferably from 0.97 to 0.99, b being zero or in the range of from 0.01 to 0.05, c being in the range of from zero to 0.02, and d being in the range of from zero to 0.04, preferably from 0.01 to 0.02,
M1 is at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, preferably at least one of Al, Mg, Ti, Mo, W and Zr, and more preferably exactly one of Al, Mg, Ti, Mo, W and Zr, a + b + c = 1 , b + c > zero.
In other embodiments, TM is nickel.
Some metals are ubiquitous such as sodium, calcium or zinc and traces of them virtually present everywhere, but such traces 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 TM. Analogously, traces of sulfate that may stem from the precursor manufacture are neglected as well.
Inventive cathode active materials are excellently suited for making cathodes for lithium-ion batteries and especially for all-solid state lithium-ion batteries. They are particularly well suited in combination with a polycrystalline cathode active material with an average (median) diameter in the range of from 9 to 16 pm, for example in a volume (or weight) ratio of inventive cathode active material to polycrystalline cathode active material in the range of from 1 :2 to 1 :10, preferably 3:7 to 1 :5. Such blends have a high volumetric energy density.
The element composition of said polycrystalline cathode active material may be the same as the element composition of inventive cathode active material or be different. For example, said polycrystalline cathode active material may have a general formula Lii+xiTM’i-xiO2 wherein TM’ is a combination of nickel and at least one of Co and Mn and, optionally, at least one dopant selected from Al, Mg, W, Mo, Nb, Ta, Zr and Ti, wherein the percentage of nickel is at least 80 mol-%, referring to the sum of Ni, Co and Mn if present, preferably at least 90 mol-%.
In one embodiment of the present invention, TM’ is nickel or corresponds to general formula (I a)
(NiaCOb’Mnc’)i-d’M2d’ (I a) with a’ being in the range of from 0.8 to 0.99, preferably from 0.9 to 0.95, b’ being zero or in the range of from 0.01 to 0.1 , preferably from 0.02 to 0.5, c’ being in the range of from zero to 0.2, preferably from 0.03 to 0.05, and d’ being in the range of from zero to 0.1 , preferably from 0.01 to 0.05,
M2 is at least one of Al, Mg, Ti, Mo, W and Zr, and a + b + c = 1 , and b + c > zero.
Polycrystalline cathode active materials is comprised of secondary particles that are agglomerates of primary particles. Preferably, polycrystalline cathode active material is comprised of spherical secondary particles that are agglomerates of platelet primary particles.
In one embodiment of the present invention, the pressed density of such blends is in the range of from 3.6 to 4.8 g/cm3, determined at a pressure of 250 MPa, preferred are 3.80 to 4.80 g/cm3.
A further aspect of the present invention refers to electrodes comprising at least one electrode active material according to the present invention. They are particularly useful for lithium-ion batteries, with a liquid non-aqueous electrolyte or with a solid electrolyte. Lithium-ion batteries comprising at least one electrode according to the present invention exhibit a good discharge behavior. Electrodes comprising at least one electrode active material according to the present invention are hereinafter also referred to as inventive cathodes or cathodes according to the present invention. Specifically, inventive cathodes contain
(A) at least one electrode active material selected from inventive cathode active material or preferably a blend from inventive cathode active material and a polycrystalline cathode active material,
(B) carbon in electrically conductive form, and, optionally,
(C) a binder, also referred to as binders or binders (C), and, preferably,
(D) a current collector.
In a preferred embodiment, inventive cathodes contain
(A) 69 to 98 % by weight electrode active material selected from inventive cathode active material or preferably a blend from inventive cathode active material and a polycrystalline cathode active material,
(B) 1 to 30 % by weight of carbon in electrically conductive form, and, optionally,
(C) to 15 % by weight of binder, percentages referring to the sum of (A), (B) and (C).
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, and from combinations of at least two of the foregoing.
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 homo-pol- ypropylene, 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-diphe- nylethylene and a-methylstyrene.
Another preferred binder (C) is polybutadiene.
Other suitable binders (C) are selected from polyethylene oxide (PEO), cellulose, carboxymethylcellulose, polyimides and polyvinyl alcohol.
In one embodiment of the present invention, binder (C) 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 (C) may be selected from cross-linked or non-cross-linked (co)polymers.
In a particularly preferred embodiment of the present invention, binder (C) 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 (C) 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 electrode active material. In other embodiments, inventive cathodes may comprise 0.1 up to less than 1% by weight of binder(s).
Inventive cathodes used in lithium-ion batteries with liquid electrolytes usually contain a binder. Inventive cathodes used in so-called all-solid-state lithium-ion batteries - or “solid-state batteries” - usually contain some solid electrolyte and, optionally, a binder.
In embodiments wherein inventive cathodes are incorporated into a solid-state battery, inventive cathodes comprise a solid-state electrolyte. Such solid-state is solid at ambient temperature.
In one embodiment of the present invention, such solid electrolyte has a lithium-ion conductivity at 25 °C of > 0.1 mS/cm, preferably in the range of from 0.1 to 30 mS/cm, measurable by, e.g., impedance spectroscopy.
In one embodiment of the present invention, such solid electrolyte comprises U3PS4, P-U3PS4 or U3I nCI6, yet more preferably argyrodite-type LiePSsCI.
In one embodiment of the present invention, solid electrolyte is selected from the group consisting of U2S-P2S5, Li2S-P2Ss-Lil, Li2S-P2Ss-Li2O, Li2S-P2Ss-Li2O-Lil, Li2S-SiS2-P2Ss-Lil, U2S-P2S5- ZmSn wherein m and n are positive numbers and Z is a member selected from the group consisting of germanium, gallium and zinc, Li2S-SiS2-Li3PO4, Li2S-SiS2-LiyPOz, wherein y and z are positive numbers, U7P3S11, U3PS4, U11S2PS12, U7P2S8I, and Li7-r-2sPS6-r-sXr wherein X is chlorine, bromine or iodine, and the variables are defined as follows:
0.8 < r < 1.7
0 < s < (-0.25 r) + 0.5.
A particularly preferred example of solid electrolytes is LiePSsCI, thus, r = 1.0 and s = zero.
In one embodiment of the present invention,
In one embodiment of the present invention, inventive cathodes for solid-state batteries contain solid electrolytes in the range of from 5 to 40% by weight.
In one embodiment of the present invention, inventive cathodes for solid-state batteries contain in the range of from 5 to 40% by weight solid electrolyte and in the range of from 0.5 to 3% by weight of carbon (B).
A further aspect of the present invention is a battery, containing at least one cathode comprising inventive electrode 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, metallic lithium, silicon, indium 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-al- kylene 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-di- methoxyethane, 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)
Figure imgf000017_0001
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. In another embodiment, R1 is fluorine and R2 and R3 are each hydrogen.
Another preferred cyclic organic carbonate is vinylene carbonate, formula (IV).
Figure imgf000018_0001
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 further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPFe, LiBF4, LiCICU, 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, LiCIC>4, with particular preference being given to LiPF6 and LiN(CF3SO2)2-
In one 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.
In solid-state batteries, solid electrolyte may serve as separator.
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 provides for 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, aircrafts 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 is further illustrated by the following working examples.
Average particle diameters (D50) were determined by SEM image analysis. Percentages are % by weight unless specifically noted otherwise. LiOH H2O was purchased from Sigma Aldrich. U2CO3 was purchased from Alfa Aesar. NiO (as precursor) was purchased from Alfa Aesar.
In step (e), ultra-pure water purified in accordance with Milli Q® laboratory water systems from Merck was used.
The manufacture of base electrode active materials was performed in a box furnace, type: tube furnace, model Nabertherm RT 50-250/13, with an alumina tube.
I. Manufacture of inventive cathode active materials
1.1 Step (a.1): Manufacture of a base material, B-CAM.1 , TM = Ni
NiO was purchased as a powder (325 mesh) from Alfa Aesar with an average primary particle size of 1 pm.
Calcination to lithium nickel oxide, B-CAM.1 :
Subsequently, nickel oxide powder was mixed with LiOH H2O at a molar ratio of Li : Ni of 1.1 :1 and calcined in a flow of pure oxygen (100 cm3/min) at 825 °C for 6 h, followed by annealing at 680 °C for 6 h. The heating rate was 100 K/h. After cooling, the black brick-like material was ground into a fine powder for 15 min. Particulate lithium nickel oxide, B-CAM.1 , was obtained and sieved using a mash size of 45 pm. (D50) of B-CAM.1 : 7.0 pm.
Calcination to lithium nickel oxide, B-CAM.2:
Subsequently, nickel oxide powder was mixed with LiOH H2O at a molar ratio of Li : Ni of 1.1 :1 and calcined in a flow of pure oxygen (100 cm3/min) at 780 °C for 6 h, followed by annealing at 680 °C for 6 h. The heating rate was 100 K/h. After cooling, the black brick-like material was ground into a fine powder for 15 min. Particulate lithium nickel oxide, B-CAM.2, was obtained and sieved using a mash size of 45 pm. (D50) of B-CAM.1 : 3.0 pm.
1.2 Manufacture of CAM.1
1.2.1 Mixing with lithium carbonate
Step (b.1):
B-CAM.1 and Li2COs in a molar ratio of 2.5 : 1 were mixed in a mortar with pestle for 5 minutes. A mixture was obtained that was converted into cylindrical pellets (diameter 1.3 cm, height 0.5 cm) by using a pressure of 100 MPa. Step (c.1): The above pellets were placed into alumina crucibles and heated to 750°C for 40 h and 20 h at 680 °C. The melting point of Li2CO3 is 720°C.
Step (d.1): They were then cooled to ambient temperature by natural cooling, rate about 100 K/h. The resultant solid mass was crushed manually in a mortar to obtain a powder.
Step (e.1): Sub-step 1 : An amount of 1 g powder from step (d.1) was immersed into 30 ml ice- cold (0 °C) ultrapure water and stirred vigorously for a minute. The slurry was allowed to settle. Supernatant water was removed by decantation, then the solid was recovered by means of a centrifuge.
Sub-step 1 was repeated with water twice. Water was then removed from the solid by washing with ethanol and with acetone.
Step (f.1): The powder resulting from step (e.1) was then heated to 700°C for 3 hours under conditions otherwise like in step (a.1). After natural cooling to ambient temperature, CAM.1 was ground in a mortar for 3 minutes. CAM.1 was obtained.
Steps (b.2) to (f.2): the above protocol was repeated but with B-CAM.2 as starting material. Inventive CAM.2 was obtained.
Figure 1 shows that both CAM.1 and CAM.2 consist of non-agglomerated, octahedral singlecrystalline particles. The particle size depended on the base materials B-CAM.1 or B-CAM.2 and were D50 » 7 pm (CAM.1) and D50 » 3 pm (CAM.2), respectively. The XRD patterns for CAM.1 and CAM.2 are shown in Figure 2. It is thereby shown that Lii+xNii.xO2 with x < 0.02 was obtained.
II. Cathode and coin cell manufacture
11.1 Cathode manufacture
11.1.1 Cathode manufacture for CAM.1
General procedure for batteries with a liquid electrolyte:
The cathode slurries necessary for cathode preparation were prepared by mixing a 5 wt% binder solution of polyvinylidene difluoride (PVDF, Solef 5130, Solvay) in /V-methyl-2-pyrroli- done (NMP, > 99.5%, Merck KGaA) with 5 wt% conductive carbon black (Super-P, TIMCAL Ltd.) and NMP in a planetary centrifugal mixer (DAC 150.1 FVZ-K) three times for 5 min at 2000 rpm. Afterwards, the either B-CAM.1 or CAM.1 was added to the slurry in an open mixing cup was used. The mixture was then stirred again for 5 min at 2000 rpm, yielding a homogenous deep black slurry. Using a motorized film applicator (MTI Corporation, MSK-AFA-II-VC-FH Tape Casting Coater ), the slurry was then immediately coated on 0.03 mm thick aluminum foil using a blade film applicator with a slit height of 60 pm for B-CAM.1 or CAM.1 to obtain areal loadings of 3 mgCAM cm-2. The obtained tapes were dried at 120 °C in vacuo for 12 hours and pressed at 100 MPa.
For cathodes for all solid-state batteries:
The cathode composite consisted of 63 wt% inventive cathode active material, 36 wt% LialnCle (NEI) and 1 wt% carbon fibers (Aldrich), which were mixed by hand grinding for 15 min. The cathode powder was pelletized at 400 MPa and the areal loading was ~4 mgcAM cnr2.
11.2 Coin cell manufacture/liquid electrolyte:
CR2032 lithium-ion battery cells (“LIB”) were assembled in an argon-filled glovebox (H2O < 0.5 ppm and O2 < 0.5 ppm) and comprised a cathode (12 mm diameter) according to III.1 , a GF/D glass microfiber or Celgard 2500 separator (16 mm diameter; GE Healthcare Life Science, Whatman), a lithium metal anode (14 mm diameter), and 75 pl of electrolyte, consisting of 1.0 M LiPF6 in 3:7 EC: EMC (ethyl methyl ketone) by weight.
For all-solid-state cells
The cathode composite (active material loading ~4 mg cm-2) was loaded onto a two-sided pelletized separator consisting of 50 mg Li3l nCh (towards the cathode side) and 30 mg Li6PSsCI (NEI) (towards the anode side). Cathode and separator were circle-shaped with a diameter of 10 mm. The cathode and separator were consolidated by pressing with 400 MPa. Afterwards, the anode was prepared by sequentially placing an indium foil (100 pm thickness, 9 mm diameter, ChemPur) and a lithium foil (100 pm thickness, 6 mm diameter, China Energy Lithium) on top of the separator. The cell was then tightly sealed, taken out of the glovebox and pressurized with 120 MPa which was maintained throughout the experiments.
11.3 Tests
LiB Test protocol: At least two cells were successfully cycled at 45°C.
The first cycle involved galvanostatic charging to 4.3 V (Li anode) or 3.7 V (InLi anode) at a rate of 0.05C, with 1C = 200 mA g-1 for CAM.1. After reaching the voltage limit, the cell was discharged to 3.0 V (Li anode) or 2.0 V (InLi anode) at 0.05C rate. After this initial cycle, a rate test followed with 0.1C, 0.2C and 0.5C for charging and discharging in the same voltage window as above. Afterwards, cycling in this voltage window at 0.5C was continued for 150 cycles.

Claims

Patent Claims
1. Process for the manufacture of a cathode active material in the form of monoliths, said process comprising the following steps:
(a) providing an electrode active material of the general formula Lii+xTMi.xO2 in particulate form wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.05 < x <+0.05,
(b) mixing said electrode active material with a compound selected from LiCI, KCI, CsCI, and IJ2CO3 and combinations of at least two of them,
(c) heating the mixture obtained in step (b) to a temperature that corresponds to the melting point of U2CO3 or up to 50°C higher than the melting point of LiCI, KCI, CsCI, or U2CO3, respectively,
(d) cooling the melt from step (c) to temperature a temperature below 300°C, thereby obtaining a solid material,
(e) washing the solid material obtained from step (d) with water or with a water/Ci-C2- alcohol mixture or a water/acetone mixture.
2. Process according to claim 1 wherein the weight ratio of cathode active material and compound^) selected from LiCI, KCI, CsCI, and U2CO3 and combinations of at least two of them in step (b) is in the range of from 6:1 to 1 :1.
3. Process according to claim 1 or 2 comprising a step (f) that includes a thermal treatment at a temperature in the range of from 500 to 725°C.
4. Process according to any of the preceding claims wherein in step (b), electrode active material provided in step (a) is mixed with LiOH and a compound selected from LiCI, KCI, CsCI, and U2CO3 and combinations of at least two of them.
5. Process according to any of the preceding claims wherein the cathode active material provided in step (a) has an average particle diameter (D50) in the range of from 2 to 8 pm.
6. Process according to any of the preceding claims wherein the mixture obtained in step (b) is converted into a pellet before heat treatment according to step (c).
7. Process according to any of the preceding claims wherein step (e) is performed at a temperature in the range of from -5 to +5°C.
8. Cathode active material comprising non-agglomerated octahedral crystals of the general formula Lii+xTMi.xO2 wherein TM is nickel or a combination of nickel and at least one of Co, Mn, Al, Mg, Ti, Zr, Nb, W, or Mo, wherein at least 95 mol-% of TM is nickel, and wherein -0.02 < x <+0.02.
9. Cathode active material according to claim 8 comprising up to 2 mol-% particulate IJ2CO3.
10. Cathode active material according to claim 8 or 9 wherein at least 50% of the particles have an octahedral shape.
11. Cathode active material according to any of the claims 8 to 10 wherein the span (D90)- (D10), divided by (D50), is in the range of from 1.0 to 1.4.
12. Use of a particulate cathode active material according to any of claims 8 to 11 in or for the manufacture of a lithium-ion battery.
13. Use of a particulate cathode active material according to any of claims 8 to 11 in or for the manufacture of an all-solid-state lithium-ion battery.
14. Cathode comprising
(A) at least one cathode active material selected from a cathode active material according to any of claims 8 to 11 alone or in a blend with a polycrystalline cathode active material,
(B) carbon in electrically conductive form,
(C) optionally, a binder, and
(D) a current collector.
15. Cathode according to claim 14 comprising
(A) 69 to 98 % by weight cathode active material,
(B) 1 to 30 % by weight of carbon in electrically conductive form, and, optionally,
(C) 1 to 15 % by weight of binder, percentages referring to the sum of (A), (B) and (C).
PCT/EP2023/078676 2022-10-24 2023-10-16 Cathode active materials in the form of monoliths, a process for their manufacture, and their use Ceased WO2024088810A1 (en)

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