Positive electrode active material and method for manufacturing a positive electrode active material

Abstract

The present invention relates to a positive electrode active material for rechargeable batteries, wherein the positive electrode active material comprises lithium, oxygen, nickel, cobalt, and manganese, wherein the positive electrode active material is a powder comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image in a field of view of at least 45 μm x at least 60 μm, wherein the atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 95.0 at%, as determined by ICP-OES; having an atomic content of Al, relative to the total amount of Ni, Co, and Mn, of 0.3 to 3.0 at%, as determined by ICP-OES; wherein the atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, as determined by ICP-OES; wherein the atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 3.0 to 35.0 at%, as determined by ICP-OES; wherein the positive electrode active material further comprises: aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis, and cobalt and has an atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis.

Description

[0001] Positive electrode active material and method for manufacturing a positive electrode active material

[0002] TECHNICAL FIELD

[0003] This invention relates to a positive electrode active material comprising lithium, oxygen, nickel cobalt and optionally manganese having an enriched amount of aluminum and cobalt in the surface layer of the particles constituting the positive electrode active material. The invention also relates to a method for manufacturing a positive electrode active material having an enriched amount of aluminum and cobalt in the surface layer; a battery comprising said positive electrode active material and the use of said battery.

[0004] BACKGROUND

[0005] As the development of small and lightweight electronic products, electronic devices, communication devices and the like has advanced rapidly and a need for electric vehicles has widely emerged with respect to environmental issues, there is a demand for improvement of performance of secondary batteries used as power sources for these products. Among these, a lithium secondary battery has come into the spotlight as a high-performance battery due to the high energy density and a high reference electrode potential.

[0006] During the charging process of a secondary battery, lithium ions are removed from the cathode, transported through the electrolyte and are inserted into the anode while electrons are removed from the cathode and injected into the anode through an external circuit (charger). During the use or discharge of a secondary battery lithium ions are removed from the anode, transported through the electrolyte, and are inserted into the cathode, while electrons flow through an external circuit to provide electric work.

[0007] Commonly used cathode active materials are lithium transition metal oxides. During the charging and / or discharging of the lithium battery, the delithiated cathode active material can slowly react with the non-aqueous electrolyte or the solid electrolyte leading to a gradual degradation of the electrochemical performance of lithium batteries using such cathode active materials. It has been demonstrated that applying a surface layer on the cathode active material with metals, such as Al, ( / . e. applying a thin surface layer of the metal on the cathode active material resulting in an increased or enriched amount of said metals in the surface layer) results in a cathode active material exhibiting improved electrochemical performances as compared to their counterparts devoid of said surface layer.

[0008] WO 2022 / 096473 Al contemplates a positive electrode active material obtained after mixing and heating a Lii.oi(Nio.63Mno.22Coo.15)0.9902 compound with CO3O4 and AI2O3. However, there remains a need to provide a positive electrode active material having an improved electrochemical performance.

[0009] It is an object of the present invention to provide a positive electrode active material comprising lithium, oxygen, nickel, cobalt and optionally manganese having an enriched amount of aluminum and cobalt in the surface layer of the particles.

[0010] It is a further object of the present invention to provide a method for manufacturing a positive electrode active material comprising lithium, oxygen, nickel, cobalt and optionally manganese having an enriched amount of aluminum and cobalt in the surface layer.

[0011] It is a further object of the present invention to provide a battery comprising said positive electrode active material.

[0012] It is a further object of the present invention to provide a use of said battery.

[0013] SUMMARY OF THE INVENTION

[0014] In a first aspect an object of the invention is achieved by providing a positive electrode active material comprising lithium, oxygen, nickel, cobalt and optionally manganese having an enriched amount of aluminum and cobalt in the surface layer of the particles constituting the positive electrode active material.

[0015] The present inventors have surprisingly found that in by subjecting the lithium nickel- manganese-cobalt oxide compound to an additional treatment of CO3O4 the resulting positive electrode active material has an improved electrochemical performance, illustrated by the reduced DCR (Direct Current internal Resistant) value.

[0016] The present invention thus concerns a positive electrode active material for rechargeable batteries, wherein the positive electrode active material comprises lithium, oxygen, nickel, cobalt, and manganese, wherein the positive electrode active material is a powder comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image in a field of view of at least 45 pm x at least 60 pm, wherein the atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 95.0 at%, as determined by ICP-OES; having an atomic content of Al, relative to the total amount of Ni, Co, and Mn, of 0.3 to 3.0 at%, as determined by ICP-OES; wherein the atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, as determined by ICP-OES; wherein the atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, as determined by ICP-OES; wherein the positive electrode active material further comprises: aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis, and cobalt and has an atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis.

[0017] Without wishing to be bound by any theory the present inventors believe that the improvement in the DCR is related with the formation of an ion-conducting phase in the surface layer of the primary particles, wherein the surface layer comprises Co, Al and optionally F.

[0018] In a further aspect the invention provides a method for manufacturing a positive electrode active material comprising lithium, oxygen, nickel, cobalt and optionally manganese having an enriched amount of aluminum and cobalt in the surface layer of the particles constituting the positive electrode active material.

[0019] In a further aspect the invention provides a battery comprising said positive electrode active material. In a further aspect the invention provides a use of said battery.

[0020] BRIEF DESCRIPTION OF THE FIGURES

[0021] Figure 1 is a cross-sectional SEM image of EXI wherein A is the position of the center of a particle, where Cocenter, Alcenter, Fcenter, N i center, and M ncenter are measured, and B is the position of the edge of a particle, where Coedge, Ale ge, and Fe ge are measured.

[0022] DETAILED DESCRIPTION

[0023] In the following detailed description, preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. To the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings.

[0024] The term "comprising", as used herein and in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a composition comprising components A and B" should not be limited to compositions consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the composition are A and B. Accordingly, the terms "comprising" and "including" encompass the more restrictive terms "consisting essentially of" and "consisting of".

[0025] The term "solid-state battery" as used herein and in the claims refers to a cell or a battery that includes only solid or substantially solid-state components such as solid electrodes (e.g. anode and cathode) and a solid electrolyte.

[0026] The term "a positive electrode active material" (also known as cathode active material) as used herein and in the claims is defined as a material which is electrochemically active in a positive electrode or cathode. By active material, it must be understood to be a material capable to capture and release Li ions when subjected to a voltage change over a predetermined period of time. The term "a positive electrode" as used herein is defined as a material comprising a positive electrode active material also in addition to other components added to the positive electrode active material, which are not electrochemically active, in particular conductivity agents or binders.

[0027] In the context of the present invention the terms "solid" and "liquid" shall be considered to be a solid and liquid in standard conditions for temperature and pressure as defined by the IUPAC, unless defined otherwise. Hereby the boiling point and the melting point shall be considered to be the boiling point and the melting point at standard atmospheric pressure, i.e. at 101325 Pa, unless specified otherwise.

[0028] In the context of the present invention the contents of the elements in positive electrode active material as described herein are measured by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method, for example (but not limiting to the invention) by using an Agillent ICP 720-OES.

[0029] In the context of the present invention the particle size distribution (PSD) of the positive electrode active material described herein is defined, in particular the D50 values, as the particle size at 50% of the cumulative volume % distribution for example (but not limiting to the invention) by using a Malvern Mastersizer 3000 with Hydro MV wet dispersion accessory.

[0030] In the context of the present invention X-ray photoelectron spectroscopy (XPS) is used to analyze the surface of positive electrode active material powder particles. As appreciated by the skilled person in XPS measurement, the signal is acquired from the first few nanometers (i.e., 1 nm to 10 nm) of the uppermost part of a sample, i.e. surface layer. Worded differently, all elements measured by XPS are contained in the surface layer. In particular, the penetration depth is the distance along an axis perpendicular to a virtual line tangent to said external edge and passing trough said first point. Preferably, monochromatic Al Ka radiation (hu = 1486.6 eV) is used with a spot size of 400 p.m and measurement angle of 45 °. Preferably, a wide survey scan to identify elements present at the surface is conducted at 200 eV pass energy. Preferably, Cis peak having a maximum intensity (or centered) at a binding energy of 284.8 eV is used as a calibrate peak position after data collection. Preferably, accurate narrow scans are performed afterwards at 50 eV for at least 10 scans for each identified element to determine the precise surface composition. For example, but not limiting to the invention, for the surface analysis of positive electrode active material powder particles, XPS measurement is carried out using a Thermo Ka+ spectrometer. For example, but not limiting to the invention, curve fitting is done with CasaXPS Version2.3.19PR1.0 using a Shirley-type background treatment and Scofield sensitivity factors, wherein preferably line shape GL(30) is the Gaussian / Lorentzian product formula with 70% Gaussian line and 30% Lorentzian line.

[0031] In the context of the present invention cross-sectional SEM-EDS is used to obtain the concentrations of the relevant elements such as Ni, Mn, Co, Al, and F from the edge to the center of the positive electrode active material particles are analyzed by energy-dispersive X-ray spectroscopy (EDS). An EDS analysis of the positive electrode active material particles provides the quantitative element analysis of the cross-section wherein it is assumed that particles are spherical. Cross-sections of the positive electrode active material as described herein are prepared by an ion beam cross-section polisher (CP) instrument JEOL (IB-19530CP). Preferably, the instrument uses argon gas as beam source. Preferably, to prepare the specimen, a small amount of a positive electrode active material powder is mixed with a resin and hardener, then the mixture is heated for 10 minutes on a hot plate; and after heating, it is placed into the ion beam instrument for cutting and the settings are adjusted in a standard procedure, with a voltage of 6.5 kV for a 3 hours duration. Preferably, a particle with a diameter around D50 value as measured by PSD is selected for analysis for each sample. Preferably, the EDS is performed by JEOL JSM 7100F SEM equipment with a 50 mm2X-MaxN EDS sensor from Oxford instruments. Preferably, a straight line is set from the edge to the center point of the particle and Ni, Mn, Co, Al, and F concentrations are measured at edge and center and expressed as an at% relative to the sum of Ni, Mn, and Co content at each point.

[0032] In the framework of the present invention, at% signifies atomic percentage. The at% or "atomic percent" of a given element expression of a concentration means how many percent of all atoms in the concerned compound are atoms of said element. Further in the framework of the present invention the designation at% is equivalent to mol% or "molar percent". Positive electrode active material

[0033] In a first aspect the present invention concerns a positive electrode active material for rechargeable batteries, wherein the positive electrode active material comprises lithium, oxygen, nickel, cobalt, and optionally manganese, wherein the positive electrode active material is a powder comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image, wherein the positive electrode active material further comprises: aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis.

[0034] A highly preferred embodiment is the positive electrode active material of the invention for solid-state batteries.

[0035] A preferred embodiment is the positive electrode active material of the invention having a layered structure, preferably a layered structure of the a-NaFeO2 type, preferably a layered structure of the a-NaFeO2 type having a R-3m space group.

[0036] A preferred embodiment is the positive electrode active material of the invention having an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of at least 45.0 at%, preferably at least 50.0 at%, more preferably at least 55.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material of the invention having an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of at most 95.0 at%, preferably at most 90.0 at%, more preferably at most 85.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material of the invention having an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 95.0 at%, preferably 50.0 to 90.0 at%, more preferably 55.0 to 85.0 at%, as determined by ICP-OES.

[0037] A certain preferred embodiment is the positive electrode active material of the invention having an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 75.0 at%, preferably 50.0 to 70.0 at%, more preferably 55.0 to 65.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Co, relative to the total amount of Ni, Co, and Mn, of at least 3.0 at%, preferably at least 5.0 at%, more preferably at least 10.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Co, relative to the total amount of Ni, Co, and Mn, of at most 30.0 at%, preferably at most 25.0 at%, more preferably at most 22.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, preferably 5.0 to 25.0 at%, more preferably 10.0 to 22.0 at%, as determined by ICP-OES.

[0038] A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of at least 3.0 at%, preferably at least 5.0 at%, more preferably at least 10.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of at most 35.0 at%, or of at most 30.0 at%, preferably at most 25.0 at%, more preferably at most 20.0 at%, as determined by ICP-OES. A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 3.0 to 35.0 at%, or of 3.0 to 30.0 at%, preferably 5.0 to 25.0 at%, more preferably 10.0 to 20.0 at%, as determined by ICP-OES.

[0039] A preferred embodiment is the positive electrode active material according to the invention having an atomic content of Al, relative to the total amount of Ni, Co, and Mn, of 0.3 to 3.0 at%, preferably of 0.4 to 2.0 at%, more preferably of 0.6 to 1.0 at%, as determined by ICP-OES.

[0040] A preferred embodiment is the positive electrode active material of the invention having a Li / (Ni + Mn+Co) ratio (mol / mol), > 0.90, preferably > 0.92, more preferably > 0.95. A preferred embodiment is the positive electrode active material of the invention having a Li / (Ni + Mn+Co) ratio (mol / mol), < 1.10, preferably < 1.08, more preferably < 1.05. A preferred embodiment is the positive electrode active material of the invention having a Li / (Ni + Mn+Co) ratio (mol / mol), in the range of 0.90 - 1.10, preferably in the range of 0.92 - 1.08, more preferably in the range of 0.95 - 1.05.

[0041] A more preferred embodiment is the positive electrode active material of the invention having

[0042] - an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 95.0 at%, preferably 50.0 to 90.0 at%, more preferably 55.0 to 85.0 at%, as determined by ICP-OES;

[0043] - an atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, preferably 5.0 to 25.0 at%, more preferably 10.0 to 22.0 at%, as determined by ICP-OES;

[0044] - an atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 3.0 to 35.0 at%, or of 3.0 to 30.0 at%, preferably 5.0 to 25.0 at%, more preferably 10.0 to 20.0 at%, as determined by ICP-OES; and

[0045] - an atomic content of Al, relative to the total amount of Ni, Co, and Mn, of 0.3 to 3.0 at%, preferably of 0.4 to 2.0 at%, more preferably of 0.6 to 1.0 at%, as determined by ICP-OES.

[0046] An even more preferred embodiment is the positive electrode active material of the invention having

[0047] - an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 75.0 at%, preferably 50.0 to 70.0 at%, more preferably 55.0 to 65.0 at%, as determined by ICP-OES;

[0048] - an atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, preferably 5.0 to 25.0 at%, more preferably 10.0 to 22.0 at%, as determined by ICP-OES;

[0049] - an atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 3.0 to 35.0 at%, or of 3.0 to 30.0 at%, preferably 5.0 to 25.0 at%, more preferably 10.0 to 20.0 at%, as determined by ICP-OES; and

[0050] - an atomic content of Al, relative to the total amount of Ni, Co, and Mn, of 0.3 to 3.0 at%, preferably of 0.4 to 2.0 at%, more preferably of 0.6 to 1.0 at%, as determined by ICP-OES.

[0051] A certain preferred embodiment is the positive electrode active material of the invention comprising Li, M', F and oxygen, wherein M' comprises: - Ni in a content x, wherein 45.0 < x < 95. 0 at%, relative to M', preferably wherein 50.0 < x < 90.0 at%, relative to M', more preferably 55.0 < x < 85.0 at%, relative to M';

[0052] - Mn in a content y, wherein 3.0 < y < 35.0 at%, or wherein 3.0 < y < 30.0 at%, preferably wherein 5.0 < y < 25.0 at%, more preferably wherein 10.0 < y < 20.0 at%, relative to M',

[0053] - Co in a content z, wherein 3.0 < z < 30.0 at%, relative to M', preferably wherein 5.0 < z < 25.0 at%, more preferably wherein 10.0 < z < 22.0 at%, relative to M',

[0054] - Al in a content a, wherein 0.3 < a < 3.0 at%, relative to M', preferably wherein 0.4 < a < 2.0 at%, more preferably wherein 0.6 < a < 1.0 at%, relative to M';

[0055] - DI in a content d, wherein 0.0 < d < 2.0 at%, relative to M', wherein D is an element different from Li, Ni, Mn, Co, Al, F and oxygen;

[0056] - - wherein x, y, z, a, and d are measured by ICP-OES, and

[0057] - - wherein x+y+z+a+d is 100.0 at%.

[0058] A more certain preferred embodiment is the positive electrode active material of the invention comprising Li, M', F and oxygen, wherein M' comprises:

[0059] - Ni in a content x, wherein 45.0 < x < 75. 0 at%, relative to M', preferably wherein 50.0 < x < 70.0 at%, relative to M', more preferably 55.0 < x < 65.0 at%, relative to M';

[0060] - Mn in a content y, wherein 3.0 < y < 35.0 at%, or wherein 3.0 < y < 30.0 at%, preferably wherein 5.0 < y < 25.0 at%, more preferably wherein 10.0 < y < 20.0 at%, relative to M',

[0061] - Co in a content z, wherein 3.0 < z < 30.0 at%, relative to M', preferably wherein 5.0 < z < 25.0 at%, more preferably wherein 10.0 < z < 22.0 at%, relative to M',

[0062] - Al in a content a, wherein 0.3 < a < 3.0 at%, relative to M', preferably wherein 0.4 < a < 2.0 at%, more preferably wherein 0.5 < a < 2.0 at%, relative to M';

[0063] - DI in a content d, wherein 0.0 < d < 2.0 at%, relative to M', wherein D is an element different from Li, Ni, Mn, Co, Al, F and oxygen;

[0064] - wherein x, y, z, a and d are measured by ICP-OES, and

[0065] - wherein x+y+z+a+d is 100.0 at%. As is known to the skilled person, the positive electrode active material of the invention can comprise impurities or be doped or contain metals on the surface resulting in an overall positive electrode active material comprising one or more elements other than Li, Ni, Mn, Co, F and 0, which is reflected in the parameter "DI" used herein. A preferred embodiment is the positive electrode active material according to the invention comprising DI, wherein DI is at least one element selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, La, Mg, Mo, Nb, S, Sr, Ti, V, W, Y, Zn, and Zr; preferably Ti, Cr, Nb, S, Y, W, and Zr; more preferably Ti, Nb, W, and Zr.

[0066] In a preferred embodiment the content d is 0.0 at% < d < 1.75 at%, preferably 0.25 at% < d < 1.5 at%, more preferably 0.5 at% < d < 1.25 at%, relative to M'.

[0067] In certain preferred embodiments the positive electrode active material is according to the invention, wherein d= 0.0 at%, relative to M'.

[0068] In certain preferred embodiments the positive electrode active material consists of Li, M', F and oxygen.

[0069] In a highly preferred embodiment the positive electrode active material comprises F and a lithium transition metal oxide according to formula (I):

[0070] Uw2Nix2Mny2COz2Ala2D2d2O2 (I) wherein 0.90 < w2 < 1.10, preferably 0.92 < w2 < 1.08, more preferably 0.95 < w2

[0071] < 1.05; wherein 0.45 < x2 < 0.75, preferably 0.50 < x2 < 0.70, more preferably 0.55 < x2

[0072] < 0.65; wherein 0.03 < y2 < 0.35, or0.03 < y2 < 0.30, preferably 0.05 < y2 < 0.25, more preferably 0.10 < y2 < 0.20; wherein 0.03 < z2 < 0.30, preferably 0.05 < z2 < 0.25, more preferably 0.10 < z2

[0073] < 0.22; wherein 0.003 < a2 < 0.03, preferably 0.004 < a2 < 0.02, more preferably 0.006 < a2 < 0.01; wherein 0.0 < d2 < 0.02, preferably 0.0 < d2 < 0.001, more preferably d2 is about 0.0; and wherein x2+y2+z2+a2+d2 = 1.0.

[0074] As is known to the skilled person, the positive electrode active material of the invention can comprise impurities or be doped or contain metals on the surface resulting in an overall positive electrode active material comprising one or more elements other than Li, Ni, Mn, Co, Al and O, which is reflected in the parameter "D2" used herein. A preferred embodiment is the positive electrode active material according to the invention comprising D2, wherein D2 is at least one element selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, La, Mg, Mo, Nb, S, Sr, Ti, V, W, Y, Zn, and Zr; preferably Ti, Cr, Y, W, and Zr; more preferably Ti, W, and Zr. In certain preferred embodiments the positive electrode active material is according to the invention, wherein d2 = 0.0, relative to M2.

[0075] As appreciated by the skilled person the amount of Li, Ni, Mn, Co and Al in the positive electrode active material is measured by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). For example, but not limiting to the invention, an Agilent ICP 720-ES is used in the ICP-OES analysis.

[0076] Surface layer

[0077] The present invention provides the positive electrode active material according to the invention, wherein the positive electrode active material comprises aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis.

[0078] In a preferred embodiment the atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.5 to 6.0, preferably 2.0 to 5.0, more preferably 2.5 to 3.0, as determined by XPS analysis.

[0079] In a highly preferred embodiment the positive electrode active material of the invention comprises cobalt and has an atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis. Hence, in highly preferred embodiments the positive electrode active material is according to the invention wherein the positive electrode active material comprises:

[0080] - aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis, and

[0081] - cobalt and has an atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis.

[0082] In a more preferred embodiment the positive electrode active material of the invention has the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.30 to 0.44, preferably 0.32 to 0.42, as determined by XPS analysis.

[0083] In a preferred embodiment the positive electrode active material of the invention has a ratio COXPS / COICP of 1.50 to 2.30, wherein COXPS is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis; and COICP is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by ICP-OES.

[0084] Hence, in certain highly preferred embodiments the positive electrode active material is according to the invention wherein the positive electrode active material comprises:

[0085] - aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis,

[0086] - a ratio COXPS / COICP of 1.50 to 2.30, wherein COXPS is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis; and COICP is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by ICP-OES.

[0087] Hence, in certain highly preferred embodiments the positive electrode active material is according to the invention wherein the positive electrode active material comprises:

[0088] - aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis,

[0089] - cobalt and has an atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis; and

[0090] - a ratio COXPS / COICP of 1.50 to 2.30, wherein COXPS is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis; and COICP is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by ICP-OES.

[0091] In a more preferred embodiment the positive electrode active material is according to the invention having the ratio COXPS / COICP of 1.60 to 2.25, preferably 1.70 to 2.20, more preferably 1.75 to 2.15.

[0092] In a preferred embodiment the positive electrode active material is according to the invention further comprises F and has an atomic ratio of F to the total amount of Ni, Co, and Mn of 0.5 to 6.0, as determined by XPS analysis.

[0093] In a preferred embodiment the positive electrode active material is according to the invention having an atomic ratio of F to the total amount of Ni, Co, and Mn of 1.0 to 5.0, preferably 1.5 to 4.0, more preferably 1.8 to 3.0, as determined by XPS analysis.

[0094] In a preferred embodiment the positive electrode active material is according to the invention, wherein at least one of the primary particles has a ratio Coedge / Cocenter > 1.55, wherein Coedge is an atomic ratio of Co to the total amount of Ni, Co, and Mn at an edge of the primary particle, Cocenter is an atomic ratio of Co to the sum of Ni, Co and Mn at a center of the primary particle, and wherein Coedge and Cocenter are measured by cross-sectional SEM-EDS.

[0095] In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Coedge / Cocenter > 1.60, preferably the ratio Coedge / Cocenter > 1.65, more preferably the ratio Coedge / Cocenter > 1.70. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Coedge / Cocenter < 50.0, preferably the ratio Coedge / Cocenter < 10.0, more preferably the ratio Coedge / Cocenter < 5.0, most preferably the ratio Coedge / Cocenter < 3.0. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Coedge / Cocenter is between 1.55 and 50.0, preferably the ratio Coedge / Cocenter is between 1.60 and 10.0, more preferably the ratio Coedge / Cocenter is between 1.65 and 5.0, most preferably the ratio Coedge / Cocenter is between 1.70 and 3.0. In a certain preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Coedge / Cocenter > 1.2, preferably the ratio Coedge / Cocenter > 1.35, more preferably the ratio Coedge / Cocenter > 1.5. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Coedge / Cocenter < 50.0, preferably the ratio Coedge / Cocenter < 10.0, more preferably the ratio Coedge / Cocenter < 5.0, most preferably the ratio Coedge / Cocenter < 3.0. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Coedge / Cocenter is between 1.2 and 50.0, preferably the ratio Coedge / Cocenter is between 1.2 and 10.0, more preferably the ratio Coedge / Cocenter is between 1.35 and 5.0, most preferably the ratio Coedge / Cocenter is between 1.5 and 3.0. In a certain highly preferred embodiment the ratio Coedge / Cocenter is between 2.0 and 3.0.

[0096] In a preferred embodiment the positive electrode active material is according to the invention, wherein at least one of the primary particles has a ratio Fedge / Fcenter > 1.4, wherein Fedge is an atomic ratio of F to the total amount of Ni, Co, and Mn at an edge of the primary particle, Fcenter is an atomic ratio of F to the sum of Ni, Co and Mn at a center of the primary particle, and wherein Fedge and Fcenter are measured by cross- sectional SEM-EDS.

[0097] In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Fedge / Fcenter > 1.5, preferably the ratio Fedge / Fcenter > 1.55, more preferably the ratio Fedge / Fcenter > 1.6. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Fedge / Fcenter < 50.0, preferably the ratio Fedge / Fcenter < 10.0, more preferably the ratio Fedge / Fcenter < 5.0, most preferably the ratio Fedge / Fcenter < 3.0. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Fedge / Fcenter is between 1.4 and 50.0, preferably the ratio Fedge / Fcenter is between 1.5 and 10.0, more preferably the ratio Fedge / Fcenter is between 1.55 and 5.0, most preferably the ratio Fedge / Fcenter is between 1.65 and 3.0.

[0098] In a preferred embodiment the positive electrode active material is according to the invention, wherein at least one of the primary particles has a ratio Aledge / Alcenter > 20.0, wherein Aledge is an atomic ratio of Al to the total amount of Ni, Co, and Mn at an edge of the primary particle, Alcenter is an atomic ratio of Al to the sum of Ni, Co and Mn at a center of the primary particle, and wherein Aledge and Alcenter are measured by cross-sectional SEM-EDS.

[0099] In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Aledge / Alcenter > 30.0, preferably the ratio Aledge / Alcenter > 35.0, more preferably the ratio Aledge / Alcenter > 40.0. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Aledge / Alcenter < 200.0, preferably the ratio Aledge / Alcenter < 150.0, more preferably the ratio Aledge / Alcenter < 100.0, most preferably the ratio Aledge / Alcenter < 75.0. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the ratio Aledge / Alcenter is between 20.0 and 200.0, preferably the ratio Aledge / Alcenter is between 30.0 and 150.0, more preferably the ratio Aledge / Alcenter is between 35.0 and 100.0, most preferably the ratio Aledge / Alcenter is between 40.0 and 75.0.

[0100] In a certain highly preferred embodiment the positive electrode active material is according to invention,

[0101] • wherein at least one of the primary particles has the ratio Coedge / Cocenter between 1.55 and 50.0, preferably between 1.60 and 10.0, more preferably between 1.65 and 5.0, most preferably between 1.70 and 3.0;

[0102] • wherein at least one of the primary particles has the ratio Aledge / Alcenter between 20.0 and 200.0, preferably the ratio Aledge / Alcenter between 30.0 and 150.0, more preferably the ratio Aledge / Alcenter between 35.0 and 100.0, most preferably the ratio Aledge / Alcenter between 40.0 and 75.0; and

[0103] • optionally wherein at least one of the primary particles has the ratio Fedge / Fcenter between 1.4 and 50.0, preferably the ratio Fedge / Fcenter between 1.5 and 10.0, more preferably the ratio Fedge / Fcenter between 1.55 and 5.0, most preferably the ratio Fedge / Fcenter between 1.65 and 3.0.

[0104] In a certain highly preferred embodiment the positive electrode active material is according to invention, wherein at least one of the primary particles

[0105] • has the ratio Coedge / Cocenter between 1.55 and 50.0, preferably between 1.60 and 10.0, more preferably between 1.65 and 5.0, most preferably between 1.70 and 3.0; • has the ratio Aledge / Alcenter between 20.0 and 200.0, preferably the ratio Aledge / Alcenter between 30.0 and 150.0, more preferably the ratio Aledge / Alcenter between 35.0 and 100.0, most preferably the ratio Aledge / Alcenter between 40.0 and 75.0; and

[0106] • optionally has the ratio Fedge / Fcenter between 1.4 and 50.0, preferably the ratio Fedge / Fcenter between 1.5 and 10.0, more preferably the ratio Fedge / Fcenter between 1.55 and 5.0, most preferably the ratio Fedge / Fcenter between 1.65 and 3.0.

[0107] In a preferred embodiment the positive electrode active material is according to the invention, wherein at least one of the primary particles has a N icenter value > 45.0 at%, wherein N icenter is an atomic ratio of N i to the sum of N i , Co and Mn at a center of the primary particle, and wherein N icenter is measured by cross-sectional SEM-EDS.

[0108] In a more preferred embodiment the positive electrode active material is according to the invention, wherein the N icenter value > 50.0 at%, preferably the N icenter value > 55.0 at%, more preferably the N icenter value > 60.0 at%. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the N icenter value < 75.0 at%, preferably the N icenter value < 70.0 at%, more preferably the N icenter value < 65.0 at%. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the N icenter value is between 50.0 and 75.0 at%, preferably the N icenter value is between 55.0 and 70.0 at%, more preferably the N icenter value is between 60.0 and 65.0 at%.

[0109] In a preferred embodiment the positive electrode active material is according to the invention, wherein at least one of the primary particles has a MnCenter value > 10.0 at%, wherein MnCenter is an atomic ratio of Mn to the sum of Ni, Co and Mn at a center of the primary particle, and wherein MnCenter is measured by cross-sectional SEM-EDS.

[0110] In a more preferred embodiment the positive electrode active material is according to the invention, wherein the MnCenter value > 15.0 at%, preferably the MnCenter value > 18.0 at%, more preferably the MnCenter value > 20.0 at%. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the MnCenter value < 35.0 at%, preferably the MnCenter value < 30.0 at%, more preferably the MnCenter value < 25.0 at%. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the Mncenter value is between 15.0 and 35.0 at% 5preferably the M ncenter value is between 18.0 and 30.0 at%, more preferably the M ncenter value is between 20.0 and 25.0 at%.

[0111] In a preferred embodiment the positive electrode active material is according to the invention, wherein at least one of the primary particles has a Cocenter value > 5.0 at%, wherein Cocenter is an atomic ratio of Co to the sum of Ni, Co and Mn at a center of the primary particle, and wherein Cocenter is measured by cross-sectional SEM-EDS.

[0112] In a more preferred embodiment the positive electrode active material is according to the invention, wherein the Cocenter value > 10.0 at%, preferably the Cocenter value > 12.0 at%, more preferably the Cocenter value > 15.0 at%. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the Cocenter value < 30.0 at%, preferably the Cocenter value < 25.0 at%, more preferably the Cocenter value < 20.0 at%. In a more preferred embodiment the positive electrode active material is according to the invention, wherein the Cocenter value is between 10.0 and 35.0 at%, preferably the Cocenter value is between 18.0 and 30.0 at%, more preferably the Cocenter value is between 20.0 and 25.0 at%.

[0113] In a certain highly preferred embodiment the positive electrode active material is according to invention,

[0114] • wherein at least one of the primary particles has the N icenter value is between 50.0 and 75.0 at%, preferably the N icenter value is between 55.0 and 70.0 at%, more preferably the N icenter value is between 60.0 and 65.0 at%;

[0115] • wherein at least one of the primary particles has the M ncenter value is between 15.0 and 35.0 at%, preferably the M ncenter value is between 18.0 and 30.0 at%, more preferably the M ncenter value is between 20.0 and 25.0 at%; and

[0116] • wherein at least one of the primary particles has the Cocenter value is between 10.0 and 35.0 at%, preferably the Cocenter value is between 18.0 and 30.0 at%, more preferably the Cocenter value is between 20.0 and 25.0 at%.

[0117] In a certain highly preferred embodiment the positive electrode active material is according to invention, wherein at least one of the primary particles • has the N icenter value is between 50.0 and 75.0 at%, preferably the N icenter value is between 55.0 and 70.0 at%, more preferably the N icenter value is between 60.0 and 65.0 at%;

[0118] • has the Mncenter value is between 15.0 and 35.0 at%, preferably the Mncenter value is between 18.0 and 30.0 at%, more preferably the Mncenter value is between 20.0 and 25.0 at%; and

[0119] • the Cocenter value is between 10.0 and 35.0 at%, preferably the Cocenter value is between 18.0 and 30.0 at%, more preferably the Cocenter value is between 20.0 and 25.0 at%.

[0120] Morphology

[0121] In certain preferred embodiments the present invention provides the positive electrode active material according to the invention, wherein said positive electrode active material is a powder comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0122] Preferably, at least 30% of the particles, more preferably at least 50% of the particles, constituting the powder observed in a SEM image are the single particles and / or the secondary particles. The number of primary particles constituting the single particles and / or the secondary particles are determined in a field of view of at least 45 pm x at least 60 pm (i.e. of at least 2700 pm2), preferably of: at least 100 pm x 100 pm (i.e. of at least 10,000 pm2).

[0123] The particles in the image should be well distributed therefore avoiding overlap between particles. This can be achieved by pouring a small amount of powder sample to the adhesive attached on the SEM sample holder and blowing air to remove the excess powder.

[0124] In the context of the present invention primary particles are distinguished from each other in a SEM image by observing grain boundaries between the primary particles. A grain boundary is defined as the interface between two primary particles, preferably wherein the atomic planes of the two primary particles are aligned to different orientations and meet as a crystalline discontinuity. Certain preferred embodiments concern the positive electrode active material of the invention being said powder comprising the single particles and / or the secondary particles, wherein said powder has a median particle size D50 value of less than 15 .m, preferably less than 10 .m, more preferably less than 8 p.m. Certain preferred embodiments concern the positive electrode active material of the invention , wherein said powder has a median particle size D50 value of more than 1 .m, preferably more than 2 .m, more preferably more than 4 .m. Certain preferred embodiments concern the positive electrode active material of the invention, wherein said powder has a median particle size D50 value between 1 and 15 .m, preferably between 2 and 10 .m, more preferably between 4 and 8 p.m.

[0125] As appreciated by the skilled person the particle size distribution (PSD) D50 of the positive electrode active material powder is measured by laser diffraction particle size analysis. Preferably, the D50 is defined as a volume median particle size, more preferably the particle size at 50% of the cumulative volume% distributions obtained from the Malvern Mastersizer 3000 with Hydro MV measurements. For example, but not limiting to the invention, the particle median D50 can be measured using a Malvern Mastersizer 3000.

[0126] Method

[0127] In a second aspect the invention provides a method for manufacturing a positive electrode active material comprising the steps of: providing a lithium transition metal-based oxide core comprising lithium, oxygen, nickel, cobalt, and optionally manganese, and comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image, mixing the lithium transition metal-based oxide core with a first Co-containing compound so as to obtain a first mixture; heating said first mixture at a first heating temperature of at least 500 °C and at most 1000 °C so as to obtain a first heat-treated mixture; mixing a second Co-containing compound with said first heat-treated mixture so as to obtain a second mixture; heating said second mixture at a second heating temperature of at least 500 °C and at most 1000 °C so as to obtain a second heat-treated mixture; mixing a first Al-containing compound with said second heat-treated mixture so as to obtain a third mixture; heating said third mixture at a third heating temperature of at least 500 °C and at most 1000 °C so as to obtain a third heat-treated mixture; mixing a fluorine-containing compound and a second Al-containing compound with said third heat-treated mixture so as to obtain a fourth mixture; heating said fourth mixture at a fourth heating temperature of at least 200 °C and at most 500 °C to afford the positive electrode active material.

[0128] In a highly preferred embodiment of the method for manufacturing a positive electrode active material of the invention the positive electrode active material is according to the first aspect of the invention. As appreciated by the skilled person, in case the method for manufacturing a positive electrode active material of the invention affords the positive electrode material according to the first aspect of the invention, all embodiments directed to the positive electrode active material according to the first aspect of the invention apply mutatis mutandis to the method for manufacturing the positive electrode active material according to the first aspect of the invention. For example, the various embodiments relating to the identity and amounts of Al, Co, F and to the morphology as explained herein in the context of the positive electrode active material are equally applicable to the method for the preparation of said positive electrode active material.

[0129] In a preferred embodiment of the method the lithium transition metal-based oxide core comprises Li, M3 and oxygen, wherein M3 comprises Ni, Mn, Co and D3, wherein D3 is an element different from Li, Ni, Mn and Co, preferably D3 is at least one element selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, La, Mg, Mo, Nb, S, Sr, Ti, V, W, Y, Zn, Zr, and Zr; preferably Ti, Cr, Nb, S, Y, W and Zr; more preferably Ti, Nb, W, and Zr.

[0130] Preferably, the lithium transition metal-based oxide core used is typically prepared according to a lithiation process, which is the process wherein a mixture of a transition metal (oxidized) hydroxide precursor and a further source of lithium is heated at a temperature preferably of at least 500 °C and at most 1000 °C. Typically, the transition metal (oxidized) hydroxide precursor is prepared by coprecipitation of one or more transition metal sources, such as salts, preferably sulfates or nitrates, more preferably sulfates; of the elements Ni, Mn and / or Co, in the presence of an alkali compound, such as an alkali hydroxide e.g. sodium hydroxide and / or ammonia. Preferably, the further source of lithium is metallic lithium or a lithium salt, preferably a lithium salt such as LiOH or U2CO3.

[0131] In a preferred embodiment said lithium transition metal-based oxide core comprises Li, M3 and oxygen, wherein M3 comprises Ni, Mn, Co and D3, wherein

[0132] - Ni in a content x3, wherein 75.0 at% < x3 < 92.0 at%, preferably 78.0 at%

[0133] < x3 < 90.0 at%, more preferably 80.0 at% < x3 < 88.0 at%, relative to M3;

[0134] - Mn in a content y3, wherein 0.0 at% < y3 < 20.0 at%, preferably 1.0 at% < y3 < 15.0 at%, more preferably 2.0 at% < y3 < 10.0 at%, relative to M3;

[0135] - Co in a content z3, wherein 0.0 at% < z3 < 20.0 at%, preferably 1.0 at% < z3 < 15.0 at%, more preferably 2.0 mol% < z3 < 10.0 mol%, relative to M3,

[0136] - D3 in a content d3, wherein 0.0 at% < d3 < 1.75 at%, preferably 0.0 at% < d3 < 1.5 at%, more preferably 0.0 at% < d3 < 1.25 at%, most preferably d3 is about 0.0 at%, relative to M3;

[0137] - wherein x3, y3, z3 and d3 are measured by ICP-OES, and

[0138] - wherein x3 + y3 + z3 + d3 = 100.0 at%.

[0139] In a preferred embodiment the atomic content of Co from the Co-containing compound mixed with the lithium transition metal-based oxide core is at least 0.1 at% and at most 4.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core, preferably at least 0.5 at% and at most 3.0 at%, more preferably at least 1.0 at% and at most 2.5 at%, even more preferably at least 1.5 at% and at most 2.5 at%, most preferably about 2.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core.

[0140] In a preferred embodiment the atomic content of Co from the Co-containing compound mixed with the second heat-treated mixture is at least 0.1 at% and at most 4.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core, preferably at least 0.2 at% and at most 3.0 at%, more preferably at least 0.5 at% and at most 2.5 at%, most preferably at least 1.0 at% and at most 2.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core.

[0141] In a preferred embodiment said first and second Co-containing compound is CO3O4, CoO, CO2O3, CoSO4, CO(OH)2, CO(NO3)2, COCOS, preferably CO3O4.

[0142] In a preferred embodiment LiOH is mixed with the lithium transition metal-based oxide core with the first Co-containing compound so as to obtain the first mixture, preferably in a range between 1.0 and 10.0 at% relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core, preferably 3.0 and 7.0 at%, most preferably in a range between 4.0 and 6.0 at%, most preferably about 5.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metalbased oxide core.

[0143] In a preferred embodiment LiOH is mixed with said second Co-containing compound with said first heat-treated mixture so as to obtain the second mixture, preferably in a range between 1.0 and 10.0 at% relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core, preferably 3 and 7 at%, most preferably in a range between 4 and 6 at%, most preferably about 5 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core.

[0144] In a preferred embodiment the atomic content of Al from the first Al-containing compound mixed with the second heat-treated mixture is at least 0.05 at% and at most 1.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core, preferably at least 0.1 at% and at most 0.8 at%, more preferably at least 0.15 at% and at most 0.6 at%, most preferably at least 0.2 at% and at most 0.5 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core.

[0145] In a preferred embodiment the atomic content of Al from the second Al-containing compound mixed with the third heat-treated mixture is at least 0.05 at% and at most 1.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metalbased oxide core, preferably at least 0.1 at% and at most 0.8 at%, more preferably at least 0.15 at% and at most 0.6 at%, most preferably at least 0.2 at% and at most 0.5 at%, relative to the total amount of N i, Co, and Mn in the lithium transition metalbased oxide core.

[0146] In a preferred embodiment said first and second Al-containing compound is AI2O3, AI(OH)3, AIO(OH), Al2(SO4)3, preferably AI2O3.

[0147] In a preferred embodiment the atomic content of F from the F-containing compound mixed with the third heat-treated mixture is at least 0.1 at% and at most 2.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metal-based oxide core, preferably at least 0.5 at% and at most 1.5 at%, more preferably at least 0.7 at% and at most 1.3 at.%, most preferably at least 0.8 at % and at most 1.0 at%, relative to the total amount of Ni, Co, and Mn in the lithium transition metalbased oxide core.

[0148] In a preferred embodiment said F-containing compound is PVDF homopolymer, a PVDF copolymer, a PVDF-HFP polymer (hexa-fluoro propylene), and a PTFE polymer, preferably PVDF.

[0149] In a preferred embodiment the heating said first mixture at the first heating temperature of at least 700 °C and at most 800 °C, preferably about 775 °C, between 1-20 h, preferably about 12 h, so as to obtain the first heat-treated mixture.

[0150] In a preferred embodiment the heating said second mixture at the second heating temperature of at least 700 °C and at most 800 °C, preferably about 750 °C, between 1-20 h, preferably about 12 h, so as to obtain the second heat-treated mixture.

[0151] In a preferred embodiment the heating said third mixture at the third heating temperature of at least 700 °C and at most 800 °C, preferably about 750 °C, between 1-20 h, preferably about 10 h, so as to obtain the third heat-treated mixture.

[0152] In a preferred embodiment the heating said fourth mixture at the fourth heating temperature of at least 300 °C and at most 450 °C, preferably about 375°C, between 1-10 h, preferably about 5 h, so as to obtain the fourth heat-treated mixture.

[0153] Product-by-process In a third aspect the invention concerns the positive electrode active material obtainable by the method according to the second aspect of the invention. As appreciated by the skilled person all embodiments directed to the positive electrode active material according to the first aspect of the invention and / or the method according to the second aspect of the invention apply mutatis mutandis to the positive electrode active obtainable by the method according to the invention. For example, the various embodiments relating to the identity and amounts Al, Co, F and to the morphology as explained herein in the context of the positive electrode active material or the method for manufacturing said positive electrode active material are equally applicable to the positive electrode active material obtainable by the method for the preparation of the positive electrode active material.

[0154] Battery

[0155] In a fourth aspect the invention concerns a battery comprising the positive electrode active material according to the first aspect of the invention and / or the positive electrode active material obtainable by the method according to the third aspect of the invention.

[0156] In a preferred embodiment the battery is a solid-state battery.

[0157] In a preferred embodiment, the solid-state battery comprises a polymer-based electrolyte, preferably a polymer-based solid electrolyte, more preferably the polymer-based solid electrolyte is polymer comprising oxyethylene units, most preferably the polymer-based solid electrolyte is polyethylene oxide. The present invention is not limited to a particular polyethylene oxide having a specific weight average molecular weight Mw. Such polymers are commercially available in a variety of different number average molecular weight. Preferably the polyethylene oxide has a weight average molecular weight Mwof less than 5,000,000 g / mol and more than 50,000 g / mol, preferably a weight average molecular weight Mwof less than 3,000,000 g / mol and more than 100,000 g / mol, more preferably a weight average molecular weight Mwof less than 2,000,000 g / mol and more than 500,000 g / mol, most preferably a weight average molecular weight Mwof about 1,000,000 g / mol.

[0158] In a highly preferred embodiment, the battery is a polymer solid-state battery. Preferably, the solid-state battery further comprises an anode comprising anode active material. Suitable electrochemically active anode materials are those known in art. For example, the anode may comprise graphitic carbon, metallic lithium or a metal alloy comprising lithium, such as Li-In alloy, as the anode active material.

[0159] In a preferred embodiment the battery according to the invention, has a DCR.2-DCR.1 value of less than 400 Q, preferably less than 300 Q, more preferably less than 200 Q, most preferably less than 150 Q. As appreciated by the skilled person the DCR.1 and DR.C2 value are determined as explained under point E2) of the examples described below

[0160] Use

[0161] In a fifth aspect the present invention concerns a use of the positive electrode active material according to the first aspect of the invention and / or the positive electrode active material obtainable by the method according to the third aspect of the invention in a battery.

[0162] A preferred embodiment is the use of the positive electrode active material in a battery, preferably a solid-state-battery, more preferably a polymer solid-state- battery, to reduce the DCR. value of the battery.

[0163] In a sixth aspect the present invention concerns a use of the battery according to invention in either one of a portable computer, a tablet, a mobile phone, an energy storage system, an electric vehicle or in a hybrid electric vehicle, preferably in an electric vehicle or in a hybrid electric vehicle.

[0164] EXAMPLES

[0165] EXPERIMENTAL TESTS USED IN THE EXAMPLES

[0166] The following analysis methods are used in the Examples:

[0167] A) Inductively coupled plasma - optical emission analysis (ICP-OES)

[0168] The contents of the elements in positive electrode active material examples and comparative example as described herein below are measured by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method using an Agillent ICP 720-OES. 1 gram of a powder sample is dissolved into 50 mL high purity hydrochloric acid in an Erlenmeyer flask. The flask is covered by a watch glass and heated on a hot plate at 380 °C until complete dissolution of the sample. After being cooled to room temperature, the solution and the rinsing water of Erlenmeyer flask are transferred to a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with DI water up to the 250 mL mark, followed by complete homogenization. An appropriate amount of solution is taken out by pipette and transferred into a 250 mL volumetric flask for the 2nddilution, where the volumetric flask is filled with internal standard and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this solution is used for ICP-OES measurement. The contents of Ni, Mn, Co, and Al are expressed as wt.% of the total of these contents.

[0169] B) Particle size

[0170] The PSD is measured using a Malvern Mastersizer 3000 with Hydro MV wet dispersion accessory after dispersing examples as described herein below of positive electrode active material powders in an aqueous medium. To improve the dispersion of the positive electrode active material powder examples, sufficient ultrasonic irradiation and stirring is applied, and an appropriate surfactant is introduced. D50 is defined as the particle size at 50% of the cumulative volume % distribution.

[0171] C) X-ray Photoelectron Spectroscopy (XPS)

[0172] In the present invention, X-ray photoelectron spectroscopy (XPS) is used to analyze the surface of positive electrode active material powder particles. In XPS measurement, the signal is acquired from the first few nanometers (e.g., 1 nm to 10 nm) of the uppermost part of a sample, i.e., surface layer. Therefore, all elements measured by XPS are contained in the surface layer.

[0173] For the surface analysis of positive electrode active material powder particles, XPS measurement is carried out using a Thermo K-o+ spectrometer. Monochromatic Al Ko radiation (hu = 1486.6 eV) is used with a spot size of 400 p.m and measurement angle of 45 °. A wide survey scan to identify elements present at the surface is conducted at 200 eV pass energy. Cis peak having a maximum intensity (or centered) at a binding energy of 284.8 eV is used as a calibrate peak position after data collection. Accurate narrow scans are performed afterwards at 50 eV for at least 10 scans for each identified element to determine the precise surface composition. Curve fitting is done with CasaXPS Version2.3.19PR1.0 using a Shirley-type background treatment and Scofield sensitivity factors. The fitting parameters are according to Table la. Line shape GL(30) is the Gaussian / Lorentzian product formula with 70% Gaussian line and 30% Lorentzian line.

[0174] Table la. XPS fitting parameter for Ni2p3, Mn2p3, Co2p3, AI2p3, and FIs.

[0175] For Al, Ni, Co, and Mn peaks, constraints are set for each defined peak according to Table lb.

[0176] Table lb. XPS fitting constraints for Al, Ni, Co, and Mn peak fitting.

[0177] The Al and F surface contents as determined by XPS are expressed as atomic fractions of Al and F, respectively, in the surface layer of the particles divided by the total content of Ni, Mn, and Co, in said surface layer.

[0178] D) Cross-section energy-dispersive X-ray spectroscopy (CS-EDS)

[0179] DI) Cross-section preparation

[0180] Cross-sections of the positive electrode active material examples and comparative examples as described herein below are prepared by an ion beam cross-section polisher (CP) instrument JEOL (IB-19530CP). The instrument uses argon gas as beam source.

[0181] To prepare the specimen, a small amount of a positive electrode active material powder is mixed with a resin and hardener, then the mixture is heated for 10 minutes on a hot plate. After heating, it is placed into the ion beam instrument for cutting and the settings are adjusted in a standard procedure, with a voltage of 6.5 kV for a 3 hour duration. D2) Energy-dispersive X-ray spectroscopy (EDS) analysis

[0182] Using the sample of the positive electrode active materials prepared according to method DI) above, the concentrations of Ni, Mn, Co, Al, and F from the edge to the center of the positive electrode active material particles are analyzed by energy- dispersive X-ray spectroscopy (EDS). A particle with a diameter around D50 value as measured by PSD according to Section B) is selected for analysis for each sample. The EDS is performed by JEOL JSM 7100F SEM equipment with a 50 mm2X-MaxN EDS sensor from Oxford instruments. An EDS analysis of the positive electrode active material particles provides the quantitative element analysis of the cross-section wherein it is assumed that particles are spherical or approximately spherical. So that the center point of a particle's cross-section is approximately the center point of the particle. Typically, the cross-sections geometric center may be taken as their center. A straight line is set from an edge to the center point of the particle and Ni, Mn, Co, Al, and F concentrations are measured at edge and center and expressed as an at% relative to the sum of Ni, Mn, and Co content at each point.

[0183] E) Polymer cell test

[0184] El) Polymer cell preparation

[0185] El.l) Solid polymer electrolyte (SPE) preparation

[0186] A solid polymer electrolyte (SPE) is prepared according to the process as follows: Step 1) Mixing polyethylene oxide (PEO, 1,000,000 g / mol, Alfa Aesar) with lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI, > 98.0 %, TCI) in acetonitrile anhydrous 99.8 wt% (Aldrich), using a mixer for 30 minutes at 2,000 revolutions per minute (rpm). The mass ratio of polyethylene oxide to LiTFSI is 3.0.

[0187] Step 2) Pouring the mixture from Stepl) into a Teflon dish and drying at 25 °C for 12 hours.

[0188] Step 3) Detaching the dried SPE from the dish and punching the dried SPE in order to obtain SPE disks having a thickness of 300 pm and a diameter of 19 mm.

[0189] El.2) Positive electrode preparation

[0190] A positive electrode is prepared according to the process as follows:

[0191] Step 1) Preparing a polymer electrolyte mixture comprising polyethylene oxide (PEO, 100,000 g / mol, Alfa Aesar) solution in anisole anhydrous 99.7 wt% (Sigma-Aldrich) and Lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI, > 98.0 %, TCI) in acetonitrile. The mixture has a ratio of PEO : LiTFSI of 74 : 26 by weight.

[0192] Step 2) Mixing the polymer electrolyte mixture prepared from Step 1) with a positive electrode active material and a conductor powder (Super P, Timcal) in acetonitrile solution with a ratio of 21 : 75 : 4 by weight so as to prepare a slurry mixture. The mixing is performed by a homogenizer for 45 minutes at 5,000 rpm.

[0193] Step 3) Casting the slurry mixture from Step 2) on one side of a 20 pm-thick aluminum foil with 100 pm coater gap.

[0194] Step 4) Drying the slurry-casted foil at 30 °C for 12 hours followed by punching in order to obtain catholyte electrodes having a diameter of 14 mm.

[0195] E1.3) Negative electrode preparation

[0196] A Li foil (diameter 16 mm, thickness 500 pm) is prepared as a negative electrode.

[0197] El.4) Polymer cell assembling

[0198] The coin-type polymer cell is assembled in an argon-filled glovebox with an order from bottom to top: a 2032 coin cell can, a positive electrode prepared from section Cl.2, a SPE prepared from section Cl.l, a gasket, a negative electrode prepared from section Cl.3, a spacer, a wave spring, and a cell cap. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.

[0199] E2) Testing method

[0200] Each cell is cycled at 80 °C using a Toscat-3100 computer-controlled galvanostatic cycling stations (Toyo). The coin cell testing procedure uses a 1C current definition of 160 mA / g in the 4.4-3.0 V / Li metal window range according to the schedule below: Step 1) Charging in a constant current mode with C-rate of 0.05 with an end condition of 4.4 V followed by 10 minutes rest.

[0201] Step 2) Discharging in a constant current mode with C-rate of 0.05 with an end condition of 3.0 V followed by 10 minutes rest.

[0202] Step 3) Charging in a constant current mode with C-rate of 0.05 up to SOC 50% and measure the DCR at a pulse current in 0.15C and the pulse length 10s to obtain DCR1.

[0203] The DCR. is calculated by following equation:

[0204] DCR = (V before pulse - V after pulse) / applied pulse current)

[0205] After DCR measurement, charging is continued with an end condition of 4.4 V. Step 4) Switching to a constant voltage mode and keeping 4.4 V for 60 hours.

[0206] Step 5) Discharging in a constant current mode with C-rate of 0.05 with an end condition of 3.0 V.

[0207] 6) Repeat the step 3 to obtain DCR2.

[0208] The present invention is further illustrated in the following examples:

[0209] Comparative Example 1

[0210] A positive electrode active material powder labelled as CEX1 was obtained through a solid-state reaction between a lithium source and a nickel-based transition metal source. The process was running as follows:

[0211] Step 1) Precursor preparation: A transition metal oxidized-hydroxide powder having a metal composition Ni0.63Mn0.22Co0.15 was prepared by a co-precipitation process in a large-scale continuous stirred tank reactor (CSTR) with mixed nickel manganese cobalt sulfates, sodium hydroxide, and ammonia.

[0212] Step 2) First mixing: the precursor prepared from Step 1) was mixed with U2CO3 in an industrial blender so as to obtain a first mixture having a lithium to metal ratio of 0.85.

[0213] Step 3) First firing: The first mixture from Step 2) was fired at 900°C for 10 hours in dry air atmosphere so as to obtain a first fired cake. The first fired cake was grinded so as to obtain a first fired powder.

[0214] Step 4) Second mixing: the first fired powder from Step 3) was mixed with LiOH in an industrial blender so as to obtain a second mixture having a lithium to metal ratio of 1.05.

[0215] Step 5) Second firing: the second mixture from Step 4) was fired at 930°C for 10 hours in dry air, followed by a crushing (bead milling) and sieving process so as to obtain a second fired powder.

[0216] Step 6) Third mixing: the second fired powder from Step 5) was mixed with 2 mol% of Co from CO3O4 powder and 5 mol% of LiOH with respect to the total molar contents of Ni, Mn, and Co in an industrial blender so as to obtain a third mixture.

[0217] Step 7) Third firing: the third mixture from Step 6) was fired at 775°C for 12 hours in dry air so as to produce a third fired powder labelled as CEX1. The powder has a D50 of 6.4 pm, as determined by laser diffraction. CEX1 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0218] Comparative Example 2

[0219] A positive electrode active material CEX2 was prepared according to the following process:

[0220] Step 1) Mixing 1 kg of the CEX1 powder with 2 grams of alumina (AI2O3) nano-powder for 30 minutes at 1000 rpm.

[0221] Step 2) Firing the mixture obtained from Step 1) in a furnace under the flow of an oxidizing atmosphere at 750°C for 10 hours.

[0222] Step 3) Mixing 1 kg powder from Step 2) with 2 grams of alumina (AI2O3) nanopowder and 3 grams of polyvinylidene fluoride (PVDF) powder for 30 minutes at 1000 rpm.

[0223] Step 4) Firing the mixture obtained from Step 3) in a furnace under the flow of oxidizing atmosphere at 375°C for 5 hours to produce a fired powder labelled as CEX2. The powder has a D50 of 6.4 pm, as determined by laser diffraction. CEX2 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0224] Comparative Example 3

[0225] A positive electrode active material CEX3 was prepared according to the following process:

[0226] Step 1) Mixing CEX1 with 1 mol% of Co from CO3O4 powder and 5 mol% of LiOH with respect to the total molar contents of Ni, Mn, and Co in an industrial blender so as to obtain a mixture.

[0227] Step 2) Firing: the mixture from Step 1) was fired at 750°C for 12 hours in dry air so as to produce a fired powder labelled as CEX3. The powder has a D50 of 6.4 pm, as determined by laser diffraction. CEX3 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image. Comparative Example 4

[0228] A positive electrode active material CEX4 was prepared according to the following process:

[0229] Step 1) Mixing CEX1 with 2 mol% of Co from CO3O4 powder and 5 mol% of LiOH with respect to the total molar contents of Ni, Mn, and Co in an industrial blender so as to obtain a mixture.

[0230] Step 2) Firing: the mixture from Step 1) was fired at 750°C for 12 hours in dry air so as to produce a fired powder labelled as CEX4. The powder has a D50 of 6.4 pm, as determined by laser diffraction. CEX4 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0231] Comparative Example 5

[0232] A positive electrode active material CEX5 was prepared according to the following process:

[0233] Step 1) Mixing CEX1 with 3 mol% of Co from CO3O4 powder and 5 mol% of LiOH with respect to the total molar contents of Ni, Mn, and Co in an industrial blender so as to obtain a mixture.

[0234] Step 2) Firing: the mixture from Step 1) was fired at 750°C for 12 hours in dry air so as to produce a fired powder labelled as CEX5. The powder has a D50 of 6.4 pm, as determined by laser diffraction. CEX5 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0235] Comparative Example 6

[0236] A positive electrode active material CEX6 was prepared according to the same method as CEX2, except that CEX5 is used in step 1) instead of CEX1. The powder has a D50 of 6.4 pm, as determined by laser diffraction. CEX6 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image. Example 1

[0237] A positive electrode active material EXI was prepared according to the same method as CEX2, except that CEX3 is used in step 1) instead of CEX1. The powder has a D50 of 6.4 pm, as determined by laser diffraction. EXI comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0238] Example 2

[0239] A positive electrode active material EX2 was prepared according to the same method as CEX2, except that CEX4 is used in step 1) instead of CEX1. The powder has a D50 of 6.2 pm, as determined by laser diffraction. EX2 comprises single particles and secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image.

[0240] Results

[0241] Table 2. Summary of the SEM-EDS analysis of the examples and comparative example. n.a. = not available

[0242] * the respective amounts of Co, Al, F, Ni and Mn are determined relative to the total atomic fraction of Ni+Mn+Co. Table 3. Summary of the properties of the examples and comparative example.

[0243] * as determined by ICP-OES measurement relative to the total fraction of Ni + Mn + Co + Al ** as determined by XPS measurement relative to the total atomic fraction of Ni + Mn + Co. n.a. = not available

[0244] Table 2 summarizes the cross sectional SEM-EDS analysis of examples and comparative examples with main variation in concentration of elements especially for Co, Al and F.. The edge / center values higher than 1 indicates that element is enriched on surface than center and with higher value, elements enriched more.

[0245] Table 3 summarizes the properties of examples and comparative examples. Composition of contents measured by ICP-OES indicates contents of entire particles. On the other hand, in the XPS analysis, Al or F value higher than 0 indicates that Al or F present on the surface of the positive electrode active material as associated with the XPS measurement which signal is acquired from the first few nanometers (e.g. lnm to lOnm) of the uppermost part of a sample, i.e. surface layer. The battery performance was measured with the DCR (Direct Current internal Resistant) analysis. This provides information about internal state of battery, and it is known as that with smaller value, it has better performance.

[0246] EXI and EX2 are positive electrode active materials having higher value of Coedge / Cocenter than the comparative examples. As confirmed by XPS, the EXs simultaneously have an Al and / or F enriched surface. Comparing with other CEXs, they exhibit improved electrochemical properties as indicated by lower DCR1 and DCR2 values.

Claims

CLAIMS1. A positive electrode active material for rechargeable batteries, wherein the positive electrode active material comprises lithium, oxygen, nickel, cobalt, and manganese, wherein the positive electrode active material is a powder comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image in a field of view of at least 45 pm x at least 60 pm, wherein the atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 45.0 to 95.0 at%, as determined by ICP-OES; having an atomic content of Al, relative to the total amount of Ni, Co, and Mn, of 0.3 to 3.0 at%, as determined by ICP-OES; wherein the atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 3.0 to 30.0 at%, as determined by ICP-OES; wherein the atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 3.0 to 35.0 at%, as determined by ICP-OES; wherein the positive electrode active material further comprises:- aluminum and has an atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.0 to 7.0, as determined by XPS analysis, and- cobalt and has an atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis.

2. The positive electrode active material according to claim 1 having a ratio COXPS / COICP of 1.50 to 2.30, wherein COXPS is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by XPS analysis; and COICP is the atomic ratio of Co to the total amount of Ni, Co, and Mn of 0.25 to 0.45, as determined by ICP-OES.

3. The positive electrode active material according to claim 1 or 2, wherein at least one of the primary particles has a ratio Coedge / Cocenter > 1.55, wherein Coedge is an atomic ratio of Co to the total amount of Ni, Co, and Mn at an edge of the primary particle, Cocenter is an atomic ratio of Co to the sum of Ni, Co and Mn at acenter of the primary particle, and wherein Coedge and Cocenter are measured by cross-sectional SEM-EDS.

4. The positive electrode active material according to any one of claims 1-3 further comprising fluorine and has an atomic ratio of F to the total amount of Ni, Co, and Mn of 0.5 to 6.0, as determined by XPS analysis.

5. The positive electrode active material according to claim 3 or 4, wherein the ratio COedge / COcenter > 1.60, preferably the ratio COedge / COcenter > 1.65, more preferably the ratio Coedge / Cocenter > 1.70.

6. The positive electrode active material according to any one of claims 1-5, wherein the atomic ratio of Al to the total amount of Ni, Co, and Mn of 1.5 to 6.0, as determined by XPS analysis.

7. The positive electrode active material according to any of claims 4-6, wherein the atomic ratio of F to the total amount of Ni, Co, and Mn of 1.0 to 5.0, as determined by XPS analysis.

8. The positive electrode active material according to any one preceding claim having a composition comprises F and a lithium transition metal oxide according to formula (I):Liw2Nix2Mny2COz2Ala2D2d2O2 (I) wherein 0.90 < w2 < 1.10,; wherein 0.45 < x2 < 0.75,; wherein 0.03 < y2 < 0.30; wherein 0.03 < z2 < 0.30; wherein 0.003 < a2 < 0.03; wherein 0.0 < d2 < 0.02; and wherein x2+y2+z2+a2+d2 = 1.

09. The positive electrode active material according to any of the previous claims having an atomic content of Ni, relative to the total amount of Ni, Co, and Mn, of 50.0 to 90.0 at%, more preferably 55.0 to 85.0 at%, as determined by ICP-OES.

10. The positive electrode active material according to any of the previous claims having an atomic content of Co, relative to the total amount of Ni, Co, and Mn, of 5.0 to 25.0 at%, more preferably 10.0 to 20.0 at%, as determined by ICP- OES.

11. The positive electrode active material according to any of the previous claims having an atomic content of Mn, relative to the total amount of Ni, Co, and Mn, of 5.0 to 25.0 at%, more preferably 10.0 to 20.0 at%, as determined by ICP-OES.

12. The positive electrode active material according to any one of the previous claims, wherein at least one of the primary particles has a ratio Aledge / Alcenter > 20.0, preferably the ratio Aledge / Alcenter > 30.0, more preferably the ratio Aledge / Alcenter > 40.0, wherein Aledge is an atomic ratio of Al to the total amount of Ni, Co, and Mn at an edge of the primary particle, Alcenter is an atomic ratio of Al to the total amount of Ni, Co, and Mn at a center of the primary particle, wherein Aledge, and Alcenter are measured by cross-sectional SEM-EDS.

13. The positive electrode active material according to any one of the previous claims, wherein at least one of the primary particles has a ratio Fedge / Fcenter > 1.4, preferably the ratio Fedge / Fcenter > 1.5, more preferably the ratio Fedge / Fcenter > 1.6, wherein Fedge is an atomic ratio of F to the total amount of Ni, Co, and Mn at an edge of the primary particle, Fcenter is an atomic ratio of F to the total amount of Ni, Co, and Mn at a center of the primary particle, wherein Fedge and Fcenter are measured by cross-sectional SEM-EDS.

14. A method for manufacturing a positive electrode active material, preferably the positive electrode active material according to any one of the previous claims, comprising the steps of:- providing a lithium transition metal-based oxide core comprising lithium, oxygen, nickel, cobalt, and optionally manganese, and comprising single particles and / or secondary particles, wherein each of the single particles consists of only one primary particle and each of the secondary particles consists of at least two primary particles and at most twenty primary particles as observed in a SEM image,- mixing the lithium transition metal-based oxide core with a first Co-containing compound so as to obtain a first mixture;- heating said first mixture at a first heating temperature of at least 500 °C and at most 1000 °C so as to obtain a first heat-treated mixture;- mixing a second Co-containing compound with said first heat-treated mixture so as to obtain a second mixture;- heating said second mixture at a second heating temperature of at least 500 °C and at most 1000 °C so as to obtain a second heat-treated mixture;- mixing a first Al-containing compound with said second heat-treated mixture so as to obtain a third mixture;- heating said third mixture at a third heating temperature of at least 500 °C and at most 1000 °C so as to obtain a third heat-treated mixture;- mixing a fluorine-containing compound and a second Al-containing compound with said third heat-treated mixture so as to obtain a fourth mixture;- heating said fourth mixture at a fourth heating temperature of at least 200 °C and at most 500 °C to afford the positive electrode active material.

15. A battery, preferably a polymer battery, comprising the positive electrode active material according to any of claims 1 to 13.

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