Cathode active material having a core-shell structure and method for producing the same

Abstract

(A) General formula Li 1+x TM 1-x a core material based on O2, wherein TM is a combination of Ni and at least two of Mn, Co and Al, and optionally at least one further metal selected from Mg, Ti, Zr, Nb, Ta and W, where x is in the range of -0.05 to +0.05, and the nickel content is in the range of 80 to 99 mol% of TM; (B) particles of cobalt compound(s) in which at least some of the cobalt is in the +III oxidation state; (C) a shell containing at least one oxide of B or W 1. A cathode active material comprising: The core material (A) is a polycrystalline material in which secondary particles are composed of primary particles, and particles (B) of a cobalt compound are concentrated on the surfaces of the secondary particles.

Description

[Technical Field]

[0001] The present invention provides (A) General formula Li 1+x TM 1-x a core material based on O2, wherein TM is a combination of Ni and at least two of Mn, Co and Al, and optionally at least one further metal selected from Mg, Ti, Zr, Nb, Ta and W, where x is in the range of -0.05 to +0.05, and the nickel content is in the range of 80 to 99 mol% of TM; (B) particles of cobalt compound(s) in which at least some of the cobalt is in the +III oxidation state; (C) A shell containing an oxide of at least one of B and W. The present invention relates to a cathode active material comprising: [Background technology]

[0002] Lithium-ion secondary batteries are state-of-the-art devices for energy storage. Many applications have been considered, ranging from small devices such as mobile phones and laptop computers to car batteries and other e-mobility batteries. Various battery components, such as electrolytes, electrode materials, and separators, play important roles in battery performance. Cathode materials have received particular attention. Several materials have been proposed, such as lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide. Although extensive research has been conducted, solutions found to date still require improvement.

[0003] Currently, particular interest is observed in so-called Ni-rich electrode active materials, for example cathode active materials containing 60 mol % or more of Ni relative to the total content of metals other than lithium.

[0004] US 6,921,609 discloses a method for producing a cobalt-coated cathode active material. The disclosed cobalt-coated cathode active material has improved electrochemical behavior compared to its uncoated counterpart. However, the specific capacity leaves room for improvement. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US 6,921,609 Summary of the Invention [Problem to be solved by the invention]

[0006] The objective of the present invention was to provide a cathode active material with improved specific capacity, improved cycling performance, and reduced resistance growth, as well as improved electrical conductivity and avoidance of capacity loss due to corrosion. [Means for solving the problem]

[0007] Thus, a cathode active material as defined at the outset has been found, which will also be referred to hereinafter as "the cathode active material of the present invention". The cathode active material of the present invention is a particulate material, (A) General formula Li 1+x TM 1-x a core material based on O2, wherein TM is a combination of Ni and at least two of Mn, Co and Al, and optionally at least one further metal selected from Mg, Ti, Zr, Nb, Ta and W, where x is in the range of -0.05 to +0.05, and the nickel content is in the range of 80 to 99 mol% of TM; (B) particles of cobalt compound(s) in which at least some of the cobalt is in the +III oxidation state; (C) A shell containing an oxide of at least one of B and W. Including, The core material (A) is a polycrystalline material in which secondary particles are composed of primary particles, and particles of the cobalt compound (B) are concentrated on the surfaces of the secondary particles.

[0008] The core material (A), particles (B), and shell (C) are described in more detail below. [Brief explanation of the drawings]

[0009] [Figure 1] Figure 1 shows a cross-sectional photograph of CAM.1 after cycling. [Figure 2] Figure 2 shows cross-sectional SEM images of CAM.1 after cycling with AI-based evaluation. [Figure 3] Figure 3 shows a cross-sectional SEM image of C-CAM.2 after cycling. [Figure 4] Figure 4 shows cross-sectional SEM images of C-CAM.2 after cycling with AI-based evaluation. DETAILED DESCRIPTION OF THE INVENTION

[0010] In one embodiment of the present invention, the core material (A) has an average particle size (D50) in the range of 3 to 20 μm, preferably 5 to 16 μm. The average particle size can be determined, for example, by light scattering, laser diffraction, or electroacoustic spectroscopy. The particles of the core material (A) are polycrystalline, i.e., composed of multiple primary particles, and the above particle size refers to the particle size of the secondary particles.

[0011] The shape of the primary particles is preferably platelet-like as detected by SEM / TEM imaging.

[0012] Multiple, in this context, means that hundreds or even more primary particles form a secondary particle. The core material (A) is preferably a nickel-rich cathode active material, ie, the mole % of nickel in the core material is at least 80 mole %, for example 80-99 mole %, based on the total metals in the TM. TM in the above formula comprises at least one, preferably at least two of Mn, Co and Al, for example Co and Mn, or Co and Al, or even all three, ie Mn, Co and Al.

[0013] In one embodiment of the present invention, TM is a metal combination according to general formula (I): (Ni a Co b Mn c ) 1-d M d (I) (In the formula, a is in the range of 0.80 to 0.99, preferably 0.83 to 0.95, and more preferably 0.85 to 0.91, b is in the range of 0.005 to 0.195, preferably 0.025 to 0.13, and more preferably 0.04 to 0.05; c is in the range of 0.005 to 0.195, preferably 0.025 to 0.13, and more preferably 0.04 to 0.05; d is in the range of 0 to 0.1, preferably 0; M is selected from Al, Mg, Ti, Zr, Nb, Ta, W, and combinations of at least two of the foregoing, preferably Al, and combinations of Al with at least one of the foregoing; a+b+c=1).

[0014] In another embodiment of the present invention, the variable TM corresponds to the general formula (Ia): (Ni a* Co b* Al e* ) 1-d* M 2 d* (I a) (In the formula, a * +b * +e * =1, a *is in the range of 0.80 to 0.99, preferably 0.88 to 0.95, b * is in the range of 0.005 to 0.19, preferably 0.025 to 0.1, e * is in the range of 0.002 to 0.19, preferably 0.015 to 0.04, d * is in the range of 0 to 0.1, preferably 0 to 0.02, M 2 is at least one of Mg, W, Mo, Ti or Zr).

[0015] In one embodiment of the present invention, TM corresponds to general formula (I), and x1 ranges from −0.05 to +0.05, preferably from 0.01 to 0.05. In one embodiment of the present invention, TM corresponds to general formula (Ia), and x1 ranges from −0.05 to +0.05.

[0016] Some elements are ubiquitous. In the context of the present invention, trace amounts of ubiquitous metals such as sodium, calcium, iron or zinc as impurities are not considered in the context of the present invention. Trace amounts in this context mean amounts of 0.05 mol % or less relative to the total metal content of the TM or particles (B), respectively.

[0017] Particles (B) comprise a lithium cobalt oxide compound in which at least some of the cobalt, preferably most of the cobalt, is in the +III oxidation state. The oxidation state of the cobalt in particles (B) can be determined by X-ray photoelectron spectroscopy ("XPS"), and its relative position with respect to the core material (A) can be determined by image processing such as transmission electron microscopy ("TEM") and scanning electron microscopy ("SEM"). The phase type of particles (B) can be determined by high-resolution powder X-ray diffraction ("XRD"). In a preferred embodiment, the average molar ratio of lithium to cobalt in particles (B) ranges from zero to less than 1.

[0018] In one embodiment of the present invention, the average oxidation state of cobalt in the particles (B) is in the range of +2 to +4, preferably greater than +2.5 to +3.5, and more preferably +3.0.

[0019] The molar ratio of lithium to cobalt in the particles (B) is in the range of 0 to 1, preferably greater than 0 to less than 1, or 1:1.

[0020] At least a part of the cobalt in the particles (B) is in the +III oxidation state. This includes, for example, the option that all of the cobalt in the particles (B) is in the +III oxidation state, such as in LiCoO2.

[0021] In one embodiment of the present invention, the cobalt in the particles (B) has a spinel structure of Li y1 CoO2 (0 < y1 < 0.6), LiCoO2, and LiCo y2 Ni 1-y2 O2 (0.5 < y2 < 1) in at least one form.

[0022] In one embodiment, the particles (B) are not a defined compound, but a mixture of several cobalt-containing oxides, for example, a substoichiometric lithium cobaltate compound such as LiCoO2 combined with Li 0.5 CoO2.

[0023] More preferably, the particles mainly contain LiCoO2 that can be detected by X-ray diffraction (「XRD」) with Cu radiation, Kα1 wavelength = 1.540598 Å.

[0024] In the cathode active material of the present invention, the particles (B) are concentrated on the surface of the secondary particles. Preferably, the particles (B) do not migrate into the pores of the secondary particles.

[0025] In one embodiment of the present invention, the mass ratio of the core material (A) to the particles (B) is in the range of 1000:1 to 10:1, preferably in the range of 100:1 to 20:1.

[0026] In one embodiment of the present invention, when applied to the cathode of a full cell having a graphite anode, 20 to 45% of the secondary particles of the cathode active material of the present invention exhibit cracks after 500 charge / discharge cycles at 4.2 to 3.0 V at 40° C. The occurrence of cracks is generally considered to be disadvantageous because the mechanical stability of the cathode decreases if there are many cracks and the presence of cracks inhibits the movement of lithium ions.

[0027] In one embodiment of the present invention, particles (B) have an average diameter (D50) ranging from 10 nm to 10 μm, preferably from 10 nm to 1 μm. The average diameter (D50) can be determined by measuring the average diameter of particles (B) on the surface of core material (A) using transmission electron microscopy (TEM) or scanning electron microscopy (SEM).

[0028] In one embodiment of the present invention, the cathode active material of the present invention further comprises aluminum compound(s) and titanium compound(s), or zirconium compound(s), each in particles (B).

[0029] In one embodiment of the present invention, particles (B) comprise cobalt, lithium, Al, and at least one of Ti and Zr as an additional element, and particles (B) preferably comprise more Co than any of Al, Ti, and Zr. In an embodiment in which particles (B) comprise Al and at least one additional element selected from Ti and Zr, individual particles (B) can comprise both Li and Co and at least one of Ti, Zr, and Al, while in other embodiments, individual particles comprise cobalt or any of Ti, Zr, or Al.

[0030] However, preferably, the particles (B) do not contain any of Al, Zr and Ti.

[0031] The cathode active material particles of the present invention further comprise a shell (C). The shell (C) comprises an oxide of at least one of B or W, such as B2O3, WO3, LiBO2, Li2BO7, or Li2WO4. In a preferred embodiment, the shell (C) comprises at least 90% by weight of B2O3, WO3, Li2BO7, Li2WO4, or LiBO2. More preferably, the shell (C) comprises at least 90% by weight of an oxide of B, such as B2O3, WO3, LiBO2, or Li2BO7.

[0032] In one embodiment of the present invention, the shell (C) is glassy or amorphous, and no crystalline phase is detectable by X-ray diffraction.

[0033] In one embodiment of the present invention, the shell (C) is not a complete shell, but has holes comparable to Swiss cheese, for example covering 55 to 95% of the outer surface of the secondary particle. In another embodiment, the shell (C) is not coherent, but exhibits an island structure.

[0034] In one embodiment of the present invention, the majority of the particles of the cathode active material of the present invention are coated to at least some degree, for example, up to 90-99% of all particles, as determined by SEM / EDX imaging of randomly selected samples.

[0035] In one embodiment of the present invention, the shell (C) has an average thickness, as detected by depth profile XPS, in the range of 2 nanometers to 50 nanometers, preferably 5 nanometers to 30 nanometers.

[0036] In one embodiment of the present invention, the B- or W-containing glassy phase fills the grain boundaries between the primary particles to a depth of several microns, preferably less than 3 microns, as determined by depth profile XPS.

[0037] In one embodiment of the present invention, the cathode active material of the present invention has a dielectric constant of 0.1 to 0.8 m, determined according to DIN-ISO 9277:2003-05. 2 / g.

[0038] A further aspect of the present invention relates to electrodes comprising at least one electrode active material according to the present invention. These are particularly useful for lithium-ion batteries. Lithium-ion batteries comprising at least one electrode according to the present invention exhibit good discharge behavior. An electrode comprising at least one cathode active material according to the present invention is hereinafter also referred to as a cathode according to the present invention or a cathode according to the present invention.

[0039] The cathode according to the present invention may contain additional components, including, but not limited to, a current collector such as aluminum foil, conductive carbon, and a binder.

[0040] Suitable binders 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 (co)polymerization, catalytic (co)polymerization or free radical (co)polymerization, in particular 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 also suitable. Polyacrylonitrile is particularly preferred.

[0041] 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, with polyacrylonitrile homopolymers being preferred.

[0042] In the context of the present invention, polyethylene refers not only to homopolyethylenes but also to copolymerized ethylene at least 50 mol % and up to 50 mol % of at least one further comonomer, such as α-olefins, for example propylene, butylene (1-butene), 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-pentene, and also isobutene, vinyl aromatics, for example styrene, and also (meth)acrylic acid, vinyl acetate, vinyl propionate, C1-C2 copolymers of (meth)acrylic acid. 10 -Alkyl esters, in particular methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and also copolymers of ethylene with maleic acid, maleic anhydride and itaconic anhydride. Polyethylene can be HDPE or LDPE.

[0043] In the context of the present invention, polypropylene is understood to mean not only homopolypropylene but also copolymers of propylene with at least 50 mol % copolymerized propylene and up to 50 mol % of at least one further comonomer, such as ethylene, and α-olefins, such as butylene, 1-hexene, 1-octene, 1-decene, 1-dodecene and 1-pentene. The polypropylene is preferably isotactic or essentially isotactic polypropylene.

[0044] In the context of the present invention, polystyrene is not only a homopolymer of styrene, but also a C1-C6 copolymer of acrylonitrile, 1,3-butadiene, (meth)acrylic acid, 10 -alkyl esters, divinylbenzene, in particular 1,3-divinylbenzene, copolymers with 1,2-diphenylethylene and α-methylstyrene are also understood to mean.

[0045] Another preferred binder is polybutadiene.

[0046] Other suitable binders are selected from polyethylene oxide (PEO), cellulose, carboxymethyl cellulose, polyimides and polyvinyl alcohol.

[0047] In one embodiment of the present invention, the binder has an average molecular weight M ranging from 50,000 g / mol to 1,000,000 g / mol, preferably up to 500,000 g / mol. W The (co)polymers are selected from the group consisting of:

[0048] The binder may be a crosslinked or non-crosslinked (co)polymer.

[0049] In a particularly preferred embodiment of the present invention, the binder is selected from halogenated (co)polymers, in particular fluorinated (co)polymers.Halogenated or fluorinated (co)polymers are understood to mean (co)polymers that contain at least one (co)polymerized (co)monomer having 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 include polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), vinylidene fluoride-tetrafluoroethylene copolymer, perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, and ethylene-chlorofluoroethylene copolymer.

[0050] Suitable binders are, in particular, polyvinyl alcohol and halogenated (co)polymers such as polyvinyl chloride or polyvinylidene chloride, especially fluorinated (co)polymers such as polyvinyl fluoride and especially polyvinylidene fluoride and polytetrafluoroethylene.

[0051] The cathode of the present invention may comprise 1 to 15% by weight of binder(s) relative to the cathode active material. In other embodiments, the cathode of the present invention may comprise 0.1 to less than 1% by weight of binder(s).

[0052] A further aspect of the present invention is a battery containing at least one cathode comprising the cathode active material of the present invention, carbon and a binder, at least one anode, and at least one electrolyte.

[0053] The cathode embodiment of the present invention has already been described in detail above.

[0054] The anode may contain at least one anode active material such as carbon (graphite), TiO, lithium titanium oxide, silicon, or tin. The anode may further contain a current collector, for example, a metal foil such as copper foil.

[0055] The electrolyte may include at least one non-aqueous solvent, at least one electrolyte salt, and optionally, additives.

[0056] The non-aqueous solvent for the electrolyte may be liquid or solid at room temperature and is preferably selected from polymers, cyclic or acyclic ethers, cyclic and acyclic acetals, and cyclic or acyclic organic carbonates.

[0057] Examples of suitable polymers are, in particular, polyalkylene glycols, preferably poly-C1-C4-alkylene glycols, and especially polyethylene glycols, where the polyethylene glycols may contain up to 20 mol % of one or more C1-C4-alkylene glycols. The polyalkylene glycols are preferably polyalkylene glycols with two methyl or ethyl end caps.

[0058] The molecular weight M of suitable polyalkylene glycols, especially suitable polyethylene glycols, Wmay be at least 400 g / mol.

[0059] The molecular weight M of suitable polyalkylene glycols, especially suitable polyethylene glycols, W can be up to 5,000,000 g / mol, preferably up to 2,000,000 g / mol.

[0060] Examples of suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, with 1,2-dimethoxyethane being preferred.

[0061] Examples of suitable cyclic ethers are tetrahydrofuran and 1,4-dioxane.

[0062] Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane and 1,1-diethoxyethane.

[0063] An example of a suitable cyclic acetal is 1,3-dioxane, and especially 1,3-dioxolane.

[0064] Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0065] Examples of suitable cyclic organic carbonates are compounds according to general formulas (II) and (III) [ka] (In the formula, R 1 , R 2 and R 3 can be the same or different and are selected from hydrogen and C1-C4-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, preferably R 2 and R 3 (Both cannot be tert-butyl).

[0066] In a particularly preferred embodiment, R 1 is methyl and R 2 and R 3 are each hydrogen or R 1 , R 2 and R 3 are hydrogen atoms.

[0067] Another preferred cyclic organic carbonate is vinylene carbonate of formula (IV).

[0068] [ka]

[0069] Preferably, the solvent or solvents are used in an anhydrous state, ie with a water content in the range of 1 ppm to 0.1% by weight, which can be determined, for example, by Karl Fischer titration.

[0070] The electrolyte (C) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPF, LiBF, LiClO, LiAsF, LiCF, SO, LiC(C n F 2n+1 SO2)3, lithium imide, e.g., LiN(C n F 2n+1 SO2)2 (wherein n is an integer ranging from 1 to 20), LiN(SO2F)2, Li2SiF6, LiSbF6, LiAlCl4, and compounds of the general formula (C n F 2n+1 SO2) t YLi salt wherein t=1 when Y is selected from oxygen and sulfur; when Y is selected from nitrogen and phosphorus, t=2; When Y is selected from carbon and silicon, t=3).

[0071] Preferred electrolyte salts are selected from LiC(CF3SO2)3, LiN(CF3SO2)2, LiPF6, LiBF4, LiClO4, with LiPF6 and LiN(CF3SO2)2 being particularly preferred.

[0072] In one embodiment of the present invention, the battery according to the present invention includes one or more separators by which the electrodes are mechanically separated. Suitable separators are polymer films, particularly porous polymer films, that are unreactive with metallic lithium. Particularly suitable materials for the separator are polyolefins, particularly film-forming porous polyethylene and film-forming porous polypropylene.

[0073] A separator made of polyolefin, particularly polyethylene or polypropylene, can have a porosity in the range of 35 to 45%. Suitable pore sizes are, for example, in the range of 30 to 500 nm.

[0074] In another embodiment of the present invention, the separator can be selected from a PET nonwoven fabric filled with inorganic particles. Such a separator can have a porosity in the range of 40 to 55%. Suitable pore sizes are, for example, in the range of 80 to 750 nm.

[0075] The battery according to the invention may further comprise a housing which may have any shape, for example a cube, or the shape of a cylindrical disk or a cylindrical can. In one variant, a metal foil configured as a pouch is used as the housing.

[0076] The battery according to the invention exhibits good discharge behavior, very good discharge and cycling behavior, for example at low temperatures (below 0° C., for example below −10° C.).

[0077] The battery according to the present invention may comprise two or more electrochemical cells that are combined with one another, for example, connected in series or in parallel. A series connection is preferred. In the battery according to the present invention, at least one electrochemical cell contains at least one cathode according to the present invention. Preferably, in the electrochemical cell according to the present invention, the majority of the electrochemical cells contain cathodes according to the present invention. Even more preferably, in the battery according to the present invention, all electrochemical cells contain cathodes according to the present invention.

[0078] The present invention further relates to the use of the battery according to the invention in a device, in particular a mobile device. Examples of mobile devices are vehicles, such as cars, bicycles, aircraft, or watercraft, such as boats or ships. Other examples of mobile devices are manually operated devices, such as computers, in particular laptops, phones, or powered hand tools, for example in the construction sector, in particular drills, battery-powered screwdrivers, or battery-powered staplers.

[0079] The present invention further relates to a method for producing the cathode active material of the present invention, hereinafter also referred to as the "method of the present invention" or "method according to the present invention."

[0080] The method of the present invention comprises at least five steps, (a), (b), (c), (d), and (e), which in the context of the present invention are also referred to as steps (a), (b), (c), (d), and (e), respectively. Steps (a), (b), (c), (d), and (e) are carried out sequentially. Steps (b) and (c) may be carried out sequentially or simultaneously.

[0081] The method of the present invention comprises the following steps: (a) providing an oxide or (oxy)hydroxide of TM, wherein the TM is a combination of Ni and at least two of Mn, Co, and Al, and optionally at least one further metal selected from Mg, Ti, Zr, Nb, Ta, and W, wherein the nickel content is in the range of 80-99 mol% of the TM; (b) mixing said oxide or (oxy)hydroxide with an oxide or (oxy)hydroxide of cobalt, and optionally with at least one oxide or (oxy)hydroxide of Al, Nb, Ti or Zr, thereby obtaining a premix; (c) adding a lithium source to the premix obtained in step (b) in a molar ratio of Li to TM in the range of (1+x+y) / (1-x), where x is in the range of zero to 0.05 and y is in the range of zero to 0.1, thereby obtaining a mixture; (d) calcining the mixture of step (c); (e) (e1) and (e2) below (e1) treating the calcined material from step (d) with water followed by liquid-solid separation; and (e2) adding a compound of W or preferably B to the calcined material of step (d) or the treated material from step (e1) and subjecting it to a heat treatment at a temperature in the range of 250-400°C At least one post-treatment step selected from Includes:

[0082] Steps (a) to (e) are described in detail below.

[0083] The method of the present invention starts with a precursor of the cathode active material, which is an oxide or (oxy)hydroxide of TM, where TM is a combination of Ni with at least two of Mn, Co, and Al, and optionally at least one additional metal selected from Mg, Ti, Zr, Nb, Ta, and W, with the nickel content ranging from 80 to 99 mol % of TM. Said precursor is hereinafter also referred to as the "starting material."

[0084] In one embodiment of the present invention, the starting material has an average particle size (D50) in the range of 3 to 20 μm, preferably 5 to 16 μm. The average particle size can be determined, for example, by light scattering, laser diffraction, or electroacoustic spectroscopy. The particles are usually composed of agglomerates of primary particles, and the above particle size refers to the particle size of secondary particles.

[0085] In one embodiment of the invention, the starting material has a unimodal particle size distribution. In another embodiment of the invention, the starting material has a bimodal particle size distribution. In one embodiment of the invention, the starting material has a narrow span particle size distribution, where span can be expressed as (D90-D10) / (D50), where D90 and D10 are the respective percentile values.

[0086] In one embodiment of the present invention, when an (oxy)hydroxide is used as a starting material, the starting material is 3 to 50 m 2 / g, which can be determined by nitrogen adsorption after outgassing the sample at 120°C for at least 30 minutes according to DIN ISO 9277:2010.

[0087] In one embodiment of the present invention, when oxides are used as starting materials, the starting materials are 50 to 250 m 2 / g, which can be determined by nitrogen adsorption after outgassing the sample at 120°C for at least 30 minutes according to DIN ISO 9277:2010. In one embodiment of the present invention, in step (a), an oxide of TM is provided having a water content, as determined by Karl Fischer titration, in the range of 0 to 100 ppm, preferably 1 to 50 ppm. In this context, zero means "below the level of detection." The core material (A) is preferably a nickel-rich cathode active material. The nickel content of the core material may be 50 mol % or less, e.g., 40 mol %, based on the total metals in the TM, but it is preferred that the nickel content in the core material is at least 60 mol %.

[0088] TM in the above formula includes at least one, preferably at least two of Mn, Co and Al, for example Co and Mn, or Co and Al, or Mn, Co and Al.

[0089] Optionally, the TM may include at least one metal selected from Mg, Ti, Zr, Nb, Ta, and W.

[0090] In one embodiment of the present invention, TM is a metal combination according to general formula (I): (Ni a Co b Mn c ) 1-d M d (I) (In the formula, a is in the range of 0.80 to 0.99, preferably 0.83 to 0.95, and more preferably 0.85 to 0.91, b is in the range of 0.005 to 0.195, preferably 0.025 to 0.13, and more preferably 0.04 to 0.05; c is in the range of 0.005 to 0.195, preferably 0.025 to 0.13, and more preferably 0.04 to 0.05; d is in the range of 0 to 0.1, preferably 0; M is selected from Al, Mg, Ti, Zr, Nb, Ta, W, and combinations of at least two of the foregoing, preferably Al, and combinations of Al with at least one of the foregoing; a+b+c=1).

[0091] In another embodiment of the present invention, the variable TM corresponds to the general formula (Ia): (Ni a* Co b* Al e* ) 1-d* M 2 d* (I a) (In the formula, a * +b * +e * =1, a * is in the range of 0.80 to 0.99, preferably 0.88 to 0.95, b * is in the range of 0.005 to 0.19, preferably 0.025 to 0.1, e *is in the range of 0.002 to 0.19, preferably 0.015 to 0.04, d * is in the range of 0 to 0.1, preferably 0 to 0.02, M 2 is at least one of Mg, W, Mo, Ti or Zr).

[0092] The starting material provided in step (a) usually does not contain conductive carbon, i.e., the content of conductive carbon in the starting material is less than 1% by mass, preferably 0.001 to 1.0% by mass, based on the starting material.

[0093] The starting material provided in step (a) is usually free of lithium. That is, the lithium content in the starting material provided in step (a) is less than 0.1 mass % based on the starting material, preferably in the range of 0 to 100 ppm. Lithium compounds in the starting material are usually impurities.

[0094] Again, some elements are ubiquitous. In the context of the present invention, trace amounts of ubiquitous metals such as sodium, calcium, iron or zinc are not considered as impurities. Trace amounts in this context mean amounts of 0.05 mol % or less relative to the total metal content of the starting material.

[0095] In step (b), the starting material is contacted with an oxide or (oxy)hydroxide of cobalt, and optionally up to 10% by volume of water, and optionally at least one oxide, hydroxide or oxyhydroxide of Ti, Zr, Al or Nb, and then mixed, wherein the cobalt oxide or (oxy)hydroxide has an average particle size (D50) in the range of 10 nm to 50 μm and a particle size distribution span in the range of 0.5 to 3.5.

[0096] Examples of cobalt oxides and hydroxides are CoO, Co3O4, Co(OH)2, CoOOH, and non-stoichiometric oxyhydroxides of cobalt. Preferred are Co(OH)2 and Co3O4. Examples of oxides or hydroxides or oxyhydroxides of Ti, Zr, Nb or Al that are optionally added are TiO2, Ti2O3, TiO(OH)2, TiO2·aq, Al2O3, AlOOH, Al(OH)3, Al2O3·aq, ZrO2, Zr(OH)4, ZrO2·aq, and Nb2O5, Nb2O5·aq ("niobic acid").

[0097] Step (b) can be carried out by mixing the components in a mixer, such as a high shear mixer. In laboratory experiments, ball mills and roller mills can also be used.

[0098] In one embodiment of the present invention, the molar ratio of cobalt added in step (b) is in the range of 0.5-5%, preferably 1-3% of TM.

[0099] Step (b) can be carried out with the addition of water or an organic solvent, but it is preferred that no organic solvent or water is added in sub-step (b) or any of the sub-steps.

[0100] The preferred duration of step (b) is in the range of 1 minute to 60 minutes.

[0101] In one embodiment of the present invention, step (b) is carried out by charging the starting materials provided in step (a) into a vessel and adding an oxide or (oxy)hydroxide of cobalt.

[0102] In step (b) a premix is ​​obtained.

[0103] Step (c) is adding a lithium source to the premix obtained in step (b) in a molar ratio of Li to TM in the range of (1 + x + y) / (1 - x), where x is in the range of zero to 0.05 and y is in the range of zero to 0.1, thereby obtaining a mixture. Suitable lithium sources are LiOH, Li2CO3, and Li2O2, including or containing hydrates, as well as mixtures of at least two of the foregoing, such as a mixture of LiOH and Li2O2. Step (c) may be carried out in the same vessel as step (b).

[0104] Step (d) involves firing the mixture obtained from step (b) at a temperature in the range of, for example, 550 to 800°C, preferably 575 to 775°C.

[0105] Step (d) can be carried out, for example, in a roller hearth kiln, a pusher kiln, a rotary kiln, a pendulum kiln, or in the case of laboratory scale tests, in a muffle oven.

[0106] The temperature of 550 to 800°C corresponds to the maximum temperature in step (d).

[0107] The mixture obtained in step (c) can be directly subjected to step (d). However, it is preferable to increase the temperature stepwise or increase the temperature. The stepwise increase or increase in temperature can be carried out under normal pressure or reduced pressure, for example, at 1 to 500 mbar.

[0108] Step (d) at maximum temperature can be carried out under normal pressure.

[0109] Step (d) is carried out under an oxygen-containing atmosphere, under oxygen-enriched air containing at least 80% by volume of oxygen, or under pure oxygen.

[0110] In one embodiment of the present invention, step (d) is carried out in an atmosphere having a reduced CO content, for example, a carbon dioxide content in the range of 0.01 to 500 ppm by mass, with 0.1 to 50 ppm by mass being preferred. The CO content can be determined, for example, by an optical method using infrared light. It is even more preferred to carry out step (d) in an atmosphere having a carbon dioxide content below the detection limit of, for example, an optical method based on infrared light.

[0111] In one embodiment of the present invention, step (d) is carried out in a roller hearth kiln, a pusher kiln, a rotary kiln, or a combination of at least two of the above. Rotary kilns have the advantage that the material produced therein is very homogenized. In roller hearth kilns and pusher kilns, different reaction conditions for different steps can be set very easily. For laboratory-scale tests, box furnaces, tube furnaces, and split-tube furnaces are also possible.

[0112] In one embodiment of the present invention, step (d) of the present invention is carried out under a forced flow of gas, such as air, oxygen, or oxygen-enriched air. Such a gas flow can be called a forced gas flow. Such a gas flow has a flow rate of 0.5 to 15 m per kg of the mixture from step (c). 3 The volume is determined under normal conditions (298 Kelvin and 1 atmosphere). The forced gas flow is useful for removing gaseous cleavage products such as water.

[0113] In one embodiment of the present invention, step (d) has a duration ranging from 2 hours to 30 hours, preferably from 6 hours to 24 hours. Cooling times are ignored in this context.

[0114] The method of the present invention comprises steps (e1) and (e2), i.e. a step (e1) of treating the material from step (d) with an aqueous medium, preferably water, followed by liquid-solid separation; and / or Step (e2) of adding tungsten or preferably a compound of boron to the material from step (d) or (e1), respectively, followed by heat treatment. The method includes a post-treatment step selected from the following:

[0115] More preferably, the method of the present invention comprises both steps (e1) and (e2). Steps (e1) and (e2) are described in more detail below.

[0116] In optional step (e1), the cathode active material obtained from step (d) is treated with an aqueous medium, preferably water or an aqueous solution of LiOH. The aqueous medium can have a pH value ranging from 7 to 14, preferably at least 3.5, more preferably from 5 to 7 or from 10 to 13. The pH value is measured at the start of step (e1). During step (e1), the pH value is observed to increase to at least 10, for example, 11 to 13. In embodiments where the pH value is in the range of 10 to 11 at the start of step (e1), the pH value increases from above 11 to 13. In embodiments where the pH value is in the range of 3 to less than 10 at the start of step (e1), the pH value increases from 11 to 13 during step (e1).

[0117] It is preferred that the water hardness, especially calcium, of the aqueous medium used in step (e1) has been at least partially removed. The use of demineralized water is preferred.

[0118] The pH value of the aqueous medium is influenced by substances dissolved or slurried in the aqueous medium, for example, acidic compounds such as sulfuric acid or aluminum sulfate, or bases such as LiOH or NaOH. In a preferred embodiment, the aqueous medium is water.

[0119] In one embodiment of the present invention, step (e1) is carried out at a temperature in the range of 5 to 85°C, preferably 5 to 30°C.

[0120] In one embodiment of the present invention, step (e1) is carried out at atmospheric pressure. However, it is preferred to carry out step (e1) under elevated pressure, for example at a pressure of 10 mbar to 10 bar above atmospheric pressure, or under vacuum, for example at a pressure of 50 to 250 mbar below atmospheric pressure, preferably at a pressure of 100 to 200 mbar below atmospheric pressure.

[0121] Step (e1) can be carried out in a vessel that is easily drained, for example, located above a filter device. Such a vessel may be filled with the material from step (d), and then the aqueous medium is introduced. In another embodiment, such a vessel is filled with the aqueous medium following the introduction of the material from step (d). In another embodiment, the material from step (d) and the aqueous medium are introduced simultaneously.

[0122] In one embodiment of the present invention, in step (e1), the amounts of water and electrode active material have a mass ratio in the range of 1:5 to 1:5, preferably 2:1 to 1:2.

[0123] Step (e1) can be supported by a mixing operation, such as shaking, in particular stirring or shearing.

[0124] In one embodiment of the invention, step (e1) has a duration ranging from 1 minute to 90 minutes, preferably from 1 minute to less than 60 minutes. In embodiments in which water treatment and water removal in step (e1) are performed overlappingly or simultaneously, durations of 5 minutes or more are possible.

[0125] In one embodiment of the present invention, the treatment according to step (e1) and the removal of the aqueous medium are carried out consecutively.

[0126] After or during the treatment with aqueous medium according to step (e1), the water may be removed by any type of filtration, for example in a band filter or filter press.

[0127] In one embodiment of the present invention, removal of the aqueous medium is initiated at least 5 minutes after the start of step (e1). Such removal includes partially removing water from the treated particulate electrode active material, for example, by solid-liquid separation, for example, by decantation, or preferably by filtration. The "partially removing" is also referred to as partially separating and removing.

[0128] In one embodiment of the present invention, the slurry obtained in step (e1) is discharged directly into a centrifuge, such as a decanter centrifuge or a filter centrifuge, or into a filter device, such as a suction filter, or a filter press, or a belt filter, preferably located directly below the vessel in which step (b) is carried out, after which filtration begins.

[0129] In a particularly preferred embodiment of the present invention, step (e1) and removal of the aqueous medium are carried out in a filter press or a filter device with an agitator, such as a pressure filter with an agitator or a suction filter with an agitator (e.g., German: "Ruehrfilternutsche"). After combining the starting material and the aqueous medium according to step (e1), removal of the aqueous medium is initiated by starting filtration after a maximum of 5 minutes, preferably a maximum of 3 minutes, or even immediately thereafter. On a laboratory scale, treatment and removal of the aqueous medium may be carried out in a Büchner funnel, which may be supported by manual stirring.

[0130] In a preferred embodiment, step (e1) is carried out in a filter apparatus, such as an agitated filter apparatus, which allows for agitation of the slurry or filter cake within the filter.

[0131] In one embodiment of the present invention, the removal of the aqueous medium or water according to step (e1) has a duration ranging from 1 minute to 1 hour.

[0132] In one embodiment of the present invention, the stirring in step (e1) is carried out at a speed in the range of 1 to 50 revolutions per minute ("rpm"), preferably 5 to 20 rpm. In another embodiment, it is 200 to 400 rpm.

[0133] In one embodiment of the present invention, the filter media can be selected from ceramic, sintered glass, sintered metal, organic polymer film, nonwoven fabric, and woven fabric.

[0134] In one embodiment of the present invention, step (e1) is carried out in an atmosphere having a reduced CO content, for example, a carbon dioxide content in the range of 0.01 to 500 ppm by mass, with 0.1 to 50 ppm by mass being preferred. The CO content can be determined, for example, by an optical method using infrared light. It is even more preferred to carry out step (e1) in an atmosphere having a carbon dioxide content below the detection limit of an optical method based on infrared light.

[0135] From step (e1), a solid residue is obtained, preferably in the form of a wet filter cake. The moisture content of this solid residue, in particular the filter cake, may range from 3 to 20% by weight, preferably from 4 to 9% by weight.

[0136] After step (e1), drying can be carried out, for example, under nitrogen or reduced pressure ("in vacuum") at 50 to 150°C to obtain a flowable powder.

[0137] Step (e2) comprises adding a compound of B or W, preferably boron, to the fired mixture of step (d) or the material obtained from step (e1), respectively, and carrying out a heat treatment at a temperature in the range of 250 to 400°C.

[0138] Examples of compounds of tungsten include WO3, (NH4)2WO4, Li2WO4, and Li4WO5.

[0139] Examples of boron compounds are B2O3, boric acid (B(OH)3), and lithium borate, e.g., LiBO2. Boric acid is preferred. The boron compound can be added in bulk or as a solution, e.g., an aqueous solution.

[0140] Combinations of tungsten and boron compounds are also possible.

[0141] In a preferred embodiment, step (e2) is carried out as described above, but without drying, and the compound of boron is added to the wet or even moist filter cake.

[0142] In one embodiment of the invention, the material resulting from step (d) is allowed to interact, for example, for a period ranging from 10 minutes to 5 hours at a temperature of 5 to 85°C.

[0143] In one embodiment of the present invention, the amount of tungsten or preferably boron compound added in step (e2) is in the range of 0.05-1.5 mol %, preferably 0.15-0.9 mol %, based on TM.

[0144] After the addition of the tungsten or boron compound, a heat treatment is carried out, which can be carried out in any type of oven, such as a roller hearth kiln, a pusher kiln, a rotary kiln, a pendulum kiln, or, in the case of laboratory scale tests, a muffle oven.

[0145] The temperature of the heat treatment in step (e2) may be in the range of 250 to 400° C. The temperature refers to the maximum temperature in step (e2).

[0146] In one embodiment of the present invention, the temperature is increased before reaching the desired temperature of 250 to 400° C. For example, the mixture of step (e2) is first heated to 250 to 300° C., then held constant for 10 minutes to 4 hours, and then increased to 325 to 400° C.

[0147] In one embodiment of the present invention, the heating rate in step (e2) is in the range of 0.1 to 10° C. / min.

[0148] In one embodiment of the present invention, the heat treatment step (e2) is carried out in a roller hearth kiln, a pusher kiln or a rotary kiln, or a combination of at least two of them. Rotary kilns have the advantage that the material produced therein is very homogenized. In roller hearth kilns and pusher kilns, different reaction conditions for different steps can be set very easily. In laboratory-scale experiments, box furnaces, tube furnaces and split tube furnaces can also be used.

[0149] In one embodiment of the present invention, step (e2) is carried out in an oxygen-containing atmosphere, such as a nitrogen-air mixture, a noble gas-oxygen mixture, air, oxygen, or oxygen-enriched air, or pure oxygen. In a preferred embodiment, the atmosphere in step (e2) is selected from air, oxygen, and oxygen-enriched air. The oxygen-enriched air may be, for example, a 50:50 volume ratio mixture of air and oxygen. Other options include a 1:2 volume ratio mixture of air and oxygen, a 1:3 volume ratio mixture of air and oxygen, a 2:1 volume ratio mixture of air and oxygen, and a 3:1 volume ratio mixture of air and oxygen. Pure oxygen is even more preferred.

[0150] In one embodiment of the present invention, the heat treatment in step (e2) has a duration ranging from 30 minutes to 5 hours, preferably from 60 minutes to 4 hours. In this context, the cooling time is ignored.

[0151] The present invention is further illustrated by examples. [Example]

[0152] Typically: Particle cracking was measured as follows: (1) Artificial intelligence (“AI”) is trained to recognize polished cross-sections of cathode active material particles and to ignore subsurface features of the cathode active material particles; (2) Because the cathode active material particles are in contact with the electrolyte, only the outer periphery of the cathode active material particles is traced, and the internal voids that should not be in contact with the electrolyte are ignored; (3) measuring the polished cross-sectional area of ​​the cathode active material particles; (4) The total circumference divided by the polished cross-sectional area (for normalization) is used as a quantitative indicator of cracking: the higher the P / A ratio, the more extensive the cracking in the cathode active material.

[0153] I. Cathode Active Material I.1 Preparation of the precursor, step (a.1) A stirred tank reactor was charged with deionized water and ammonium sulfate (49 g per kg of water) was added. The solution was kept at 55° C. and the pH was controlled at 12 by adding aqueous sodium hydroxide.

[0154] A tank reactor was simultaneously fed with an aqueous solution of transition metal sulfate and an aqueous solution of sodium hydroxide at a flow rate ratio of 1.8, with a total flow rate of 8 hours and a residence time of 8 hours. The transition metal sulfate solution contained Ni, Co, and Mn in a molar ratio of 91:4.5:4.5 and a total transition metal concentration of 1.45 mol / kg. The aqueous solution of sodium hydroxide was a mixture of aqueous sodium hydroxide (50% by weight) and aqueous ammonia (30% by weight) in a mass ratio of 6:1. The pH value was maintained at 12 by separately feeding the aqueous solution of sodium hydroxide. Starting from the start of all feeds, the mother liquor was continuously removed. After 27 hours, all feed flows were stopped. The resulting suspension was filtered, washed with distilled water, dried at 120 °C, and sieved to obtain the mixed transition metal (TM) oxyhydroxide precursor TM-OH.1.

[0155] The oxyhydroxide precursor TM-OH.1 thus obtained was calcined at 475° C. to produce the oxide precursor TM-O.1.

[0156] I.2 Preparation of cathode active material (pristine), steps (b.1) to (d.1) The oxide precursor TM-O.1 was mixed with 1.0 mol% Co(OH)2, 1.6 mol% Al(OH)3, and 0.3 mol% ZrO2, all relative to the total Ni, Co, and Mn in TM-O.1, and LiOH monohydrate with a Li / TM molar ratio of 1.03. This mixture was heated to 765 °C in forced oxygen for 8 hours to obtain the cathode active material B-CAM.1.

[0157] For the comparative sample, the same mixture was prepared except that Co(OH)2 was not added. After calcining the mixture, a comparative cathode active material CB.CAM.2 was obtained.

[0158] The D50 was 12.6 μm as measured using laser diffraction on a Malvern Instruments Mastersizer 3000. The residual moisture measured at 230° C. was 136 ppm.

[0159] I.3 Post-processing I.3.1. Cleaning process (e1.1) The cathode active material prepared by I.2. was poured into deionized water and stirred at ambient temperature for 5 minutes. The ratio of B-CAM.1 or CB-CAM.2 to water was 2000 g / L. The resulting slurry was filtered and dried in air at 120°C to obtain the washed cathode active material CAM.W.1(2).

[0160] I.3.2. Coating process (e2.1) The washed cathode active material CAM.W.1(2) obtained according to I.3.1. was mixed with 0.9 mol % H3BO3 in a roller mill. The mol % is based on the total of Ni, Co, and Mn in CAM.W.1(2). The resulting mixture was then heated to 300°C for 5 hours in a forced oxygen stream to obtain the cathode active materials CAM.1 and C-CAM.2, respectively.

[0161] SEM / EDX analysis revealed submicron-sized coated particles (D50 = 100-500 nm) of Co compounds (B.1) concentrated in islands on the surface of CAM.1 particles. TEM / EDX mapping of particle cross sections confirmed the absence of Co enrichment at the grain boundaries of primary particles. Surface-sensitive XPS confirmed the formation of boron shells (C) containing LiBO2 and Li2B4O7 phases on the surfaces of secondary particles of CAM.1 and C-CAM.2, and depth-profile XPS confirmed the boron coating depth of several micrometers along the grain boundaries of primary particles.

[0162] High-resolution X-ray diffraction was performed using a synchrotron light source (ALBA Synchrotron Light Source, BL04-MSPD, Spain). Rietveld refinement using the X-ray diffraction pattern of CAM.1 revealed the formation of LiCoO2 with a layered crystal structure.

[0163] I.4 Further Examples The protocols of I.1–I.3 were repeated, but the amounts of LiOH, Co(OH)2, Al(OH)3, ZrO2, H3BO3, and WO3 were as shown in Table 1.

[0164] [Table 1]

[0165] II. Cathode Active Material Testing II.1. Electrode Preparation, General Procedure II.1.1. Preparation of the cathode PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to prepare a 7.5 wt% solution. For electrode preparation, the 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 the inventive CAM.1 or the comparative cathode active material C-CAM (94 wt%) was added, and the suspension was mixed again to obtain a lump-free slurry. The solids content of the slurry was adjusted to 65%. This slurry was coated onto Al foil using a roll-to-roll coater. All electrodes were calendered before use. The thickness of the cathode material was 70 μm, with a concentration of 15 mg / cm. 2 All electrodes were dried at 105°C for 7 hours before cell assembly.

[0166] II.1.2. Fabrication of Pouch Cell Anodes Graphite and carbon black were thoroughly mixed. A CMC (carboxymethyl cellulose) aqueous solution and an SBR (styrene butadiene rubber) aqueous solution were used as binders. The graphite and carbon black mixture (cathode active material: carbon: CMC: SBR mass ratio = 96:0.5:2:1.5) was mixed with the binder solution and an appropriate amount of water to prepare a slurry suitable for electrode preparation. The obtained slurry was coated onto copper foil (thickness = 10 μm) using a roll coater and dried at room temperature. For the single-layer pouch cell test, the sample weight gain was 10 mg / cm. 2 Fixed to.

[0167] II.2 Preparation of electrolyte 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). The wt% was based on the total weight of EL Base 1. To this base electrolyte formulation, 2 wt% vinylene carbonate (VC) was added (EL Base 2).

[0168] II.3. Test Cell Construction II.3.1. Coin-shaped half cell Coin-shaped half-cells (20 mm diameter, 3.2 mm thickness) containing the cathode prepared as described in Section II.1.1 and lithium metal as the working and counter electrodes were assembled in an Ar-filled glove box. The cathode, anode, and separator were stacked in the order cathode / separator / Li foil to form half-coin cells. Then, 0.15 mL of EL base 1 described in Section II.2 was added.

[0169] II.3.2. Pouch Cell A single-layer pouch cell (70 mA h) containing the anode prepared as described in Section II.1.1. and the graphite anode prepared as described in Section II.1.2. was assembled and sealed in an Ar-filled glove box. The cathode, anode, and separator were stacked in the order cathode / separator / anode to form a single-layer pouch cell. Then, 0.8 mL of EL-Base 2 electrolyte was introduced into the stacked pouch cell.

[0170] III. Cell performance evaluation III.1. Evaluation of Coin Half-Cell Performance The cell performance was evaluated using the manufactured coin-type half cell. The initial capacity and capacity retention were measured as follows.

[0171] The coin-type half-cells according to II.3.1. were tested at room temperature over a voltage range of 4.3 to 2.7 C. In the initial cycle, delithiation was performed in CC-CV mode, i.e., a constant current (CC) of 0.05 C was applied, followed by a constant voltage (CV) of 4.3 V, maintained until a voltage of 0.02 C was reached. After a 5-minute rest, relithiation was performed at a constant current of 0.05 C to 2.7 V. The cycling current density was C / 3. The results are summarized in Table 2.

[0172] After several formation cycles in the voltage range of 4.2 to 2.85 V at C / 3, the monolayer pouch cells were tested.

[0173] [Table 2]

[0174] Judging from the SEM images, 20-45% of the particles of CAM.1 show cracks after 500 cycles. More than 45% of the particles of C-CAM.2 show cracks after 500 cycles.

Claims

1. (A) General formula Li １＋ｘ TM １－ｘ O ２ wherein TM is a combination of Ni and at least two of Mn, Co and Al, and optionally at least one further metal selected from Mg, Ti, Zr, Nb, Ta and W, and x is in the range of −0.05 to +0.05, and the nickel content is in the range of 80 to 99 mol % of TM. (B) Li, in which at least a portion of the cobalt is in the +III oxidation state and has a spinel structure. ｙ１ CoO ２ , LiCoO ２ , and LiCo ｙ２ Ni １－ｙ２ O ２ Particles of a cobalt compound or compounds selected from the group consisting of: (C) B ２ O ３ , W.O. ３ , LiBO ２ , Li ２ B ４ O ７ , and Li ２ WO ４ a shell comprising at least one compound selected from 1. A cathode active material comprising: The cathode active material, wherein the core material (A) is a polycrystalline material in which secondary particles are composed of primary particles, and particles (B) of a cobalt compound are concentrated on the surfaces of the secondary particles.

2. TM is a combination of transition metals according to general formula (I), (Ni a Co b Mr c ) 1-d M d (I) (wherein a is in the range of 0.80 to 0.99; b is in the range of 0.005 to 0.12; c is in the range of 0.005 to 0.12; d is in the range of 0 to 0.1; M is selected from Al, Mg, Ti, Zr, Nb, Ta, and W; a+b+c=1.

3. The coating is LiCoO ２ 3. The cathode active material of claim 1 or 2, comprising:

4. 3. The cathode active material of claim 1, wherein after 500 charge-discharge cycles in a range of 4.2 to 3.0 V at 40° C. in a full cell having a graphite anode, 20 to 45% of the secondary particles exhibit cracks.

5. 3. The cathode active material according to claim 1, wherein the particles (B) have an average particle size (D50) in the range of 10 nm to 1 μm, but in any case smaller than the diameter of the core (A), when the average particle size (D50) is determined by SEM or TEM.

6. The following process: (a) providing an oxide or (oxy)hydroxide of TM, wherein TM is a combination of Ni, at least two of Mn, Co and Al, and optionally at least one further metal selected from Mg, Ti, Zr, Nb, Ta and W, wherein the nickel content is in the range of 80-99 mol% of TM; (b) The oxide or (oxy)hydroxide is replaced with CoO, Co ３ O ４ , Co(OH) ２ , CoOOH, and non-stoichiometric oxyhydroxides of cobalt, and optionally at least one oxide or (oxy)hydroxide of Al, Nb, Ti, or Zr, thereby obtaining a premix; (c) adding a lithium source to the premix obtained in step (b) in a molar ratio of Li to TM in the range of (1+x+y) / (1-x), thereby obtaining a mixture, wherein x is in the range of 0 to 0.05 and y is in the range of 0 to 0.1; (d) calcining the mixture of step (c); (e) (e1) and (e2) below (e1) treating the calcined material from step (d) with water followed by liquid-solid separation; and (e2) adding a compound of B or W to the calcined material of step (d) or the treated material from step (e1) and subjecting it to a heat treatment at a temperature in the range of 250-400°C, wherein the compound of B is B ２ O ３ , boric acid (B(OH) ３ ), and lithium borate, and the compound of W is selected from WO ３ , (NH ４ ) ２ WO ４ , Li ２ WO ４ , and Li ４ WO ５ a step selected from At least one post-treatment step selected from 3. A method for making the cathode active material of claim 1, comprising:

7. 7. The method of claim 6, wherein step (d) is carried out at a temperature in the range of 550 to 800°C.

8. 7. The method of claim 6, wherein an oxide of TM having a water content in the range of 0 to 100 ppm, as determined by Karl Fischer titration, is provided in step (a).

9. 7. The method of claim 6, wherein steps (b) and (c) are carried out in different types of mixers.

10. 7. The method of claim 6, wherein step (b) is carried out dry.

11. TM is a metal combination according to general formula (I), (Ni a Co b Mr c ) 1-d M d (I) (wherein a is in the range of 0.80 to 0.99; b is in the range of 0.005 to 0.12; c is in the range of 0.005 to 0.12; d is in the range of 0 to 0.1; M is selected from Al, Mg, Ti, Zr, Nb, Ta, and W; 7. The method of claim 6, wherein a+b+c=1.

12. (A) at least one cathode active material according to claim 1 or 2; (B) carbon in a conductive state, and (C) Binder an electrode.

13. (1) at least one electrode according to claim 12; (2) at least one anode; and (3) Electrolyte A secondary battery comprising:

Images