Positive electrode active material blend

Abstract

The present disclosure provides a positive electrode active material blend comprising a first positive electrode active material powder having a particle size distribution value D501 lower than or equal to 2 μm, in particular measured by PSD, wherein the first positive electrode active material powder comprises Li, M', and 0, wherein M' comprises: Ni in a content x, wherein 45 at% ≤ x ≤ 98 at%, relative to M', Mn in a content y, wherein 0 at% < y ≤ 25 at%, relative to M', Co in a content z, wherein 0 at% < z ≤ 25 at%, relative to M', and D in a content a, wherein 0 at% ≤ a ≤ 5 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, wherein x, y, z, and a are measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES), wherein x+y+z+a is 100 at%; further comprising a second positive electrode active material powder having a particle size distribution value D502 higher than 2 pm and lower than or equal to 15 μm.

Description

DESCRIPTIONTitlePOSITIVE ELECTRODE ACTIVE MATERIAL BLENDTechnical field

[0001] The present invention relates to a positive electrode active material blend that can be suitably used for a lithium secondary battery using a solid electrolyte (referred to as "all solid-state lithium secondary battery"). Particularly, the positive electrode active material blend may present high pellet density.Description of related art

[0002] Solid-sate rechargeable batteries are of particular interest as they may reach particularly high energy density, combined with a higher level of safety because of the absence of flammable organic liquid electrolyte.

[0003] Various ways for improving the performance of solid-state rechargeable batteries are being explored. Improving positive electrode active materials presents particular challenges as a resistant layer may be formed of the positive electrode active material particles because of reactions with a solid electrolyte.Summary

[0004] The present disclosure concerns a positive electrode active material blend comprising a first positive electrode active material powder having a particle size distribution value D50i lower than or equal to 2 pm, in particular measured by PSD, wherein the first positive electrode active material powder comprises Li, M', and 0, wherein M' comprises: a. Ni in a content x, wherein 45 at% < x < 98 at%, relative to M', b. Mn in a content y, wherein 0 at% < y < 25 at%, relative to M', c. Co in a content z, wherein 0 at% < z < 25 at%, relative to M', and d. D in a content a, wherein 0 at% < a < 5 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, e. wherein x, y, z, and a are measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES),f. wherein x+y+z+a is 100 at%. further comprising a second positive electrode active material powder having a particle size distribution value D502 higher than 2 pm and lower than or equal to 15 pm, with D502 referring to a particle size at 50% of cumulative volume% distribution when measured by laser scattering method.

[0005] The inventors have found that such a positive electrode active material blend may provide increased tap density which may enhance cell performance in various ways, such as for example volumetric capacity.Detailed description

[0006] In the following detailed description, preferred embodiments are described in detail to enable practice of the present disclosure. Although the present disclosure is described with reference to these specific preferred embodiments, it will be understood that the present disclosure is not limited to these preferred embodiments. To the contrary, the present disclosure includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings. Unless otherwise indicated, it is not meant that the alternatives, modifications, and equivalents described herein are understood as separate, non-combinable, embodiments. That is, provided it is technically feasible, the different parts of the present disclosure may be combined with one another.

[0007] "ICP-OES" as used herein refers to Inductively Coupled Plasma - Optical Emission Spectrometry. The method of determining metal compositions using ICP- OES and its meaning are described herein below.

[0008] "XPS" as used herein refers to X-ray Photoelectron Spectroscopy. The method of determining metal compositions using XPS and its meaning are described herein below.

[0009] "at%" signifies atomic percentage. The at% or "atomic percent" of a given element means a percentage of atoms of said element among all atoms in a claimed composition. ICP-OES provides weight percent (wt%) of each element included in a material whose composition is determined by this technique. Conversion from wt% to at%, as is well known to the person skilled in the art, is as follows: at% of a first element Ei Eati) in a material can be converted from a given wt% of said first element Ei Ewti) in said material by applying the following formula,wherein Eawi is a standard atomic weight (molecular weight) of the first element Ei, Ewti is wt% of an ithelement Ei, Eawi is a standard atomic weight (molecular weight) of said ithelement Ei, and n is an integer which represents the number of types of all elements included in the material.

[0010] "about" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / -20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the present disclosure. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

[0011] "D50" as used herein refers to a particle size at 50% of cumulative volume% distribution when measured by laser scattering method. The method of measuring D50 by laser scattering method is described herein below. The same applies of course to D50i and D502, which apply to the first and second positive electrode active material powders respectively.

[0012] As used herein, a range of values "from X to Y" includes the endpoints X and Y.

[0013] "Milling" as used herein is the action of reducing the size of particles by a mechanical action submitting the particles to a stress. Some cracks will appear under the stress, and subsequently the particle will be broken in different parts.

[0014] "Homogeneous" as used herein may refer to a state of a blend with different powdered substances in which the components are uniformly distributed throughout the mixture. In other words, every sample of the homogeneous mixture may exhibit almost the same proportions of each substance.

[0015] In an embodiment, the first positive electrode active material powder comprises first particles, each of the first particles consisting of at least one first primary particles and at most twenty first primary particles.

[0016] In an embodiment, the second positive electrode active material powder comprises second particles, wherein each of the second particles consists of at least one second primary particle and at most twenty second primary particles.

[0017] The number of primary particles constituting the secondary particles is determined by scanning electron microscopy (SEM) in a field of view of at least about 45 pm x at least about 60 pm ( / .e. of at least about 2700 pm2), preferably of: at least about 100 pm x about 100 pm (J.e. of at least about 10,000 pm2). The particles in the image may be well distributed therefore avoiding overlapping 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. In the context of the present disclosure, primary particles may be 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.

[0018] In an embodiment of first positive electrode active material powder 55 at% < x < 95 at%, preferably 65 at% < x < 92 at%, and more preferably 70 at% < x < 90 at%, relative to M'.

[0019] In an embodiment of first positive electrode active material powder 2 at% < y < 20 at%, preferably 4 at% < y < 15 at%, and more preferably 5 at% < y < 10 at%, relative to M'.

[0020] In an embodiment of first positive electrode active material powder 2 at% < z < 20 at%, preferably 4 at% < z < 15 at%, and more preferably 5 at% < z < 10 at%, relative to M'.

[0021] In an embodiment of first positive electrode active material powder D comprises Nb, wherein 0 at% < a < 4 at%, or 0.0 at% < a < 4.0 at%, preferably 0.2 at% < a < 3.5 at%, and more preferably 0.3 at% < a < 3 or 0.3 at% < a < 3.0 at%, relative to M'.

[0022] In an embodiment of the positive electrode active material blend, the mass ratio M2: Ml of the second positive electrode active material powder to the first positive electrode active material powder is 60:40 < M2 / M1 < 90: 10. The first and second positive electrode active powders, with their D50 value ranges, mixed in these mass ratios, may provide significantly increased pellet densities, reaching pellet densities of more than 3.20 g / cm3, even more than 3.30 g / cm3. At ratiosbelow 60:40 and above 90: 10 pellet density improvement becomes less important. Advantageously M2 / M1 < 85: 15 or even M2 / M1 < 80:20. Also advantageously, 65:35 < M2 / M1 or even 70:30 < M2 / M1.

[0023] In an embodiment, D502 is not more than 15pm, advantageously not more than 10pm, more advantageously not more than 9.5pm.

[0024] In an embodiment, D502 is at least 3pm, advantageously at least 4pm, advantageously at least 5pm, advantageously at least 6pm.

[0025] In an embodiment, the ratio D502 / D50i ranges from 3.5: 1 to 6: 1, in particular from 3.7: 1 to 5.8: 1, in particular from 3.8: 1 to 5.5: 1.

[0026] In an embodiment, the second positive electrode active material powder comprises Li, M", and 0, wherein M" comprises: a. Ni in a content x", wherein 45 at% < x" < 98 at%, relative to M', b. Mn in a content y", wherein 0 at% < y" < 25 at%, relative to M', c. Co in a content z", wherein 0 at% < z" < 25 at%, relative to M', and d. D" in a content a", wherein 0 at% < a" < 5 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, e. wherein x", y", z", and a" are measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES), f. wherein x"+y"+z"+a" is 100 at%.

[0027] In an embodiment, the second positive electrode active material powder comprises second particles, wherein each of the second particles consists of at least one second primary particle and at most twenty second primary particles.

[0028] In an embodiment, the second positive electrode active material powder 55 at% < x" < 95 at%, preferably 65 at% < x" < 92 at%, and more preferably 70 at% < x" < 90 at%, relative to M".

[0029] In an embodiment, the second positive electrode active material powder 2 at% < y" < 20 at%, preferably 4 at% < y" < 15 at%, and more preferably 5 at% < y" < 10 at%, relative to M".

[0030] In an embodiment, the second positive electrode active material powder 2 at% < z" < 20 at%, preferably 4 at% < z" < 15 at%, and more preferably 5 at% < z" < 10 at%, relative to M".

[0031] In an embodiment, the second positive electrode active material powder, wherein D" comprises Nb, wherein 0 at% < a" < 4 at% or 0.0 at% < a" < 4.0 at%, preferably 0.2 at% < a" < 3.5 at%, and more preferably 0.3 at% < a" < 3 at% or 0.3 at% < a" < 3.0 at%, relative to M".

[0032] The present disclosure further concerns a method for preparing a positive electrode material blend, in particular a blend according to any embodiment or combination of embodiments herein above, comprising: a. For obtaining a first positive electrode active material powder: a.l providing a starting material comprising a Li source and a transition metal composite precursor; a.2 mixing the starting material to obtain a first mixture; a.3 heating the first mixture at a temperature between 650°C and 1000°C to obtain a heated material; a.4 providing a first intermediate material comprising the heated material; a.5 milling the first intermediate material to obtain a milled material; a.6 providing a second intermediate material comprising the milled material and a D-containing compound; a.7 mixing the second intermediate material to obtain a second mixture; and a.8 heating the second mixture at a temperature between 250°C and500°C so as to obtain a first positive electrode active material powder. b. For obtaining a second positive electrode active material powder: b.l providing a second starting material comprising a Li source and a second transition metal composite precursor; b.2 mixing the starting material to obtain a third mixture;b.3 heating the third mixture at a temperature between 650°C and 1000°C to obtain a second heated material; b.4 grinding and sieving the second heated material so as to obtain a second positive electrode active material powder; c. mixing the first and second positive electrode active material powders, so as to obtain the positive electrode active material blend.

[0033] A battery, in particular using a solid electrolyte, thus a solid state battery, comprising the positive electrode active material according to any embodiment or combination of embodiments herein above.

[0034] The present disclosure further concerns the use of a battery, in particular solid state battery, according to the present disclosure in any of its embodiments or combination of embodiments in a portable electronic device, such as portable computer, tablet, or mobile phone, in a power tool, in an energy storage system, in an uninterruptible power supply, an electric vehicle, or hybrid electric vehicle. Electric vehicles and hybrid electric vehicles include, Plug-in Hybrid Electric Vehicles, Extended Range Electric Vehicles. Electric vehicles include vehicles for passenger and freight, marine, air, aerospace and ground transportation and mobile machinery..

[0035] The following analysis methods are used in the Examples and the Comparative Example.A) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) measurement

[0036] The amount of Ni, Mn, Co, and D in the positive electrode active material powder is measured with the ICP-OES method by using an Agilent ICP 720-ES (Agilent Technologies). 2 grams of powder sample is dissolved into 10 mL of high purity hydrochloric acid (at least 37 wt% of HCI with respect to the total weight of solution) in an Erlenmeyer flask. The flask is covered by a glass and heated on a hot plate at 380 °C until complete dissolution of the precursor. After being cooled to room temperature, the solution of the Erlenmeyer flask is poured into a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with deionized water up to the 250 mL mark, followed by complete homogenization.B) Particle size analysis

[0037] The particle size distribution (PSD) of the positive electrode active material powder is measured by laser diffraction particle size analysis using a Malvern Mastersizer 3000 with a Hydro MV wet dispersion accessory after having dispersed each of the powder samples in an aqueous medium. In order to improve the dispersion of the powder, sufficient ultrasonic irradiation and stirring are applied, and an appropriate surfactant is introduced. D50 is defined as the particle size at 50% of the cumulative volume% distributions.C) Pellet density

[0038] The pressed density is measured as follows: 3 grams of powder is filled into a pellet die with a diameter "d" of 1.30 cm. A uniaxial load pressure of 207 MPa is applied to the powder in pellet die for 30 seconds. After relaxing the load, the thickness "t" of the pressed powder is measured. The pellet density (PD) is then calculatedD) Specific surface area analysis

[0039] The specific surface area of the positive electrode active material is measured with the Bruanauer-Emmett-Teller (BET) method by using a Micromeritics Tristar II 3020. A powder sample is heated at 300 °C under a nitrogen (N2) gas for 1 hour prior to the measurement in order to remove adsorbed species. The dried powder is put into the sample tube. The sample is then degassed at 30 °C for 10 minutes. The instrument performs the nitrogen adsorption test at 77 K. By obtaining the nitrogen isothermal absorption / desorption curve, the total specific surface area of the sample in m2 / g is derived.EXAMPLES

[0040] The present disclosure is further illustrated in the following examples.Positive electrode active material powder 1 (CAM1)

[0041] A positive electrode active material powder was obtained through following steps: a. Mixing step: Nio.9oMno.o4Coo.oe(OH)2 powder was homogeneously mixed with LiOH, ZrO2, Y2O3, and AI2O3 to prepare a mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co was 1.05, and wherein 0.32 at% of Zr, 0.11 at% of Y, and 0.55 at% of Al were added, relative to total amount of Ni, Mn, and Co.b. Heating step: the mixture was heated at 763 °C for 8 hours under oxygen atmosphere followed by cooling, grinding, and sieving so as to obtain a positive electrode active material powder CAM1.Positive electrode active material powder 2 (CAM2)

[0042] A positive electrode active material powder was obtained through following steps: a. Mixing step: Nio.85Mno.o7Coo.os(OH)2 powder was homogeneously mixed with LiOH to prepare a mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co was 1.01. b. Heating step: the mixture was heated at 780 °C for 10 hours under oxygen atmosphere followed by cooling, grinding, and sieving so as to obtain a positive electrode active material powder CAM2.Positive electrode active material powder 3 (CAM3)

[0043] A positive electrode active material powder was obtained through following steps: a. First mixing step: Nio.85Mno.o7Coo.os(OH)2 powder was homogeneously mixed with LiOH and Nb20s to prepare a first mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co was 1.01, and wherein 0.1 at% Nb was added relative to total amount of Ni, Mn, and Co. b. First heating step: the first mixture was heated at 880 °C for 10 hours under oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material. c. Second mixing step: the first heated material was mixed with CoSC Caq) in water to prepare the second mixture, wherein 0.5 at% Co was added relative to total amount of Ni, Mn, and Co in the first heated material. d. Second heating step: the second mixture was heated at 700 °C for 10 hours followed by cooling, grinding, and sieving to prepare a second heated material. e. Third mixing step: the second heated material was mixed with H3BO3 and WO3 to prepare a third mixture, wherein 500 ppm B and 4500 ppm W were added relative to total amount of Ni, Mn, and Co in the second heated material.f. Third heating step: the second mixture was heated at 350 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material powder CAM3.Positive electrode active material powder 4 (CAM4)

[0044] A positive electrode active material powder was obtained through following steps: a. First mixing step: Nio.85Mno.o7Coo.os(OH)2 powder was homogeneously mixed with LiOH and NbzOs to prepare a first mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co was 1.04, and wherein 0.5 mol% of Nb was added relative to total amount of Ni, Mn, and Co. b. First heating step: the first mixture was heated at 885 °C for 10 hours under oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material. c. Milling step: the first heated material was bead milled followed by filtering and drying at 110 °C for 15 hours under nitrogen atmosphere to prepare a milled material. d. Second mixing step: the milled material was mixed with LiOH homogeneously to prepare a second mixture, wherein molar ratio of Li to total amount of Ni, Mn, and Co in the second mixture is 0.99. e. Second heating step: the second mixture was heated at 700 °C for 10 hours followed by cooling, grinding, and sieving to prepare a second heated material. f. Third mixing step: the second heated material was mixed with H3BO3 and WO3 homogeneously to prepare a third mixture, wherein 500 ppm B and 4500 ppm W were added relative to total amount of Ni, Mn, and Co in the second heated material. g. Third heating step: the third mixture was heated at 350 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material powder CAM4.Comparative Example 1.1 (CEX1.1)

[0045] A positive electrode active material blend CEX1.1 was obtained by blending CAM1 and CAM3 homogeneously, wherein mass ratio of CAM1 to CAM3 is 80:20.Comparative Example 1.2 (CEX1.2)

[0046] A positive electrode active material blend CEX1.2 was obtained by blending CAM1 and CAM3 homogeneously, wherein mass ratio of CAM1 to CAM3 is 70:30.Example 1.1 (EX1.1)

[0047] A positive electrode active material blend EX1.1 was obtained by blending CAM1 and CAM4 homogeneously, wherein mass ratio of CAM1 to CAM4 is 80:20.Example 1.2 (EX1.2)

[0048] A positive electrode active material EX1.2 was obtained by blending CAM1 and CAM4 homogeneously, wherein mass ratio of CAM1 to CAM4 is 70:30.Comparative Example 2.1 (CEX2.1)

[0049] A positive electrode active material blend CEX2.1 was obtained by blending CAM2 and CAM3 homogeneously, wherein mass ratio of CAM2 to CAM3 is 80:20.Comparative Example 2.2 (CEX2.2)

[0050] A positive electrode active material blend CEX2.2 was obtained by blending CAM2 and CAM3 homogeneously, wherein mass ratio of CAM2 to CAM3 is 70:30.Example 2.1 (EX2.1)

[0051] A positive electrode active material blend EX2.1 was obtained by blending CAM2 and CAM4 homogeneously, wherein mass ratio of CAM2 to CAM4 is 80:20.Example 2.2 (EX2.2)

[0052] A positive electrode active material EX2.2 was obtained by blending blend CAM2 and CAM4 homogeneously, wherein mass ratio of CAM2 to CAM4 is 70:30.

[0053] Table 1 below summarizes the ICP-OES and PSD results of CAM1, CAM2, CAM3, and CAM4.

[0054] Table 1. Summary of ICP-OES and PSD results of CAM1, CAM2, CAM3, and CAM4.* The atomic contents analyzed by ICP-OES are relative to total contents of Ni, Mn,Co, and D, with x+y+z+a = 100at%, and x"+y"+z"+a"=100at%.

[0055] Table 2 below summarizes the blend information such as the used positive electrode active material powders and the blend ratio, and the pellet density of all the Examples and the Comparative Examples.

[0056] Table 2. Summary of the blend information and the pellet density of Examples and Comparative Examples* The mass ratio is the blended ratio of the first powder to the second powder in weight.Discussion of analytical results

[0057] According to Table 2, in 80 weight% CAM1 comprising mixtures, EX1.1 has a higher pellet density than CEX1.1, wherein EX1.1 comprising 20 weight% CAM4, having a D50 value of 1.70 pm while CEX1.1 comprises 20 weight% CAM3, having a D50 value of 2.96 pm. In 70 weight% CAM1 comprising mixtures, EX1.2 comprising 30 weight% CAM4 has a higher pellet density than CEX1.2 comprising 30 weight% CAM3.

[0058] Similarly, in 80 weight% CAM2 comprising mixtures, EX2.1 has a higher pellet density than CEX2.1, wherein EX2.1 comprising 20 weight% CAM4, having a D50 value of 1.70 pm while CEX2.1 comprises 20 weight% CAM3, having a D50 value of 2.96 pm. In 70 weight% CAM2 comprising mixtures, EX2.2 comprising 30 weight% CAM4 has a higher pellet density than CEX2.2 comprising 30 weight% CAM3.

[0059] These results thus surprisingly show that, although the D50 values of CAM3 and CAM4 are quite close, for mixtures comprising various coarser CAM materials powder (2nd powder), the admixture of a finer CAM material powder (1st powder) having a D501 value less than or equal to 2 pm exhibits up to about 7% higher pellet density.

Claims

CLAIMS

1. A positive electrode active material blend comprising a first positive electrode active material powder having a particle size distribution value D50i lower than or equal to 2 pm, in particular measured by PSD, wherein the first positive electrode active material powder comprises Li, M', and 0, wherein M' comprises: a. Ni in a content x, wherein 45 at% < x < 98 at%, relative to M', b. Mn in a content y, wherein 0 at% < y < 25 at%, relative to M', c. Co in a content z, wherein 0 at% < z < 25 at%, relative to M', and d. D in a content a, wherein 0 at% < a < 5 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, wherein x, y, z, and a are measured by inductively coupled plasma - optical emission spectroscopy ICP-OES, wherein x+y+z+a is 100 at%; further comprising a second positive electrode active material powder having a particle size distribution value D502 higher than 2 pm and lower than or equal to 15 pm, with D502 and D50i referring to particle sizes at 50% of cumulative volume% distribution when measured by laser scattering method.

2. The positive electrode active material blend according to claim 1, wherein the first positive electrode active material powder comprises first particles, each of the first particles consisting of at least one first primary particles and at most twenty first primary particles and / or wherein the second positive electrode active material powder comprises second particles, wherein each of the second particles consists of at least one second primary particle and at most twenty second primary particles.

3. The positive electrode active material blend according to claim 1 or 2, wherein 55 at% < x < 95 at%, preferably 65 at% < x < 92 at%, and more preferably 70 at% < x < 90 at%, relative to M'.

4. The positive electrode active material according to any one of claims 1 to 3, wherein 2 at% < y < 20 at%, preferably 4 at% < y < 15 at%, and more preferably 5 at% < y < 10 at%, relative to M'.

5. The positive electrode active material blend according to any one of claims 1 to 4, wherein 2 at% < z < 20 at%, preferably 4 at% < z < 15 at%, and more preferably 5 at% < z < 10 at%, relative to M'.

6. The positive electrode active material blend according to any one preceding claim, wherein D comprises Nb, wherein 0 at% < a < 4 at%, preferably 0.2 at% < a < 3.5 at%, and more preferably 0.3 at% < a < 3 at%, relative to M'.

7. The positive electrode active material blend according to any one preceding claim, wherein the mass ratio M2:M1 of the second positive electrode active material powder to the first positive electrode active material powder is 60:40 < M2 / M1 < 90: 10.

8. The positive electrode active material blend according to claim any one preceding claim, wherein the second positive electrode active material powder comprises Li, M", and O, wherein M" comprises: a. Ni in a content x", wherein 45 at% < x" < 98 at%, relative to M', b. Mn in a content y", wherein 0 at% < y" < 25 at%, relative to M', c. Co in a content z", wherein 0 at% < z" < 25 at%, relative to M', and d. D" in a content a", wherein 0 at% < a" < 5 at%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, wherein x", y", z", and a" are measured by inductively coupled plasma - optical emission spectroscopy ICP-OES, e. wherein x"+y"+z"+a" is 100 at%.

9. The positive electrode active material blend according to claim 8, wherein 55 at% < x" < 95 at%, preferably 65 at% < x" < 92 at%, and more preferably 70 at% < x" < 90 at%, relative to M".

10. The positive electrode active material blend according to any one of claims 8 to 9, wherein 2 at% < y" < 20 at%, preferably 4 at% < y" < 15 at%, and more preferably 5 at% < y" < 10 at%, relative to M".

11. The positive electrode active material blend according to any one of claims 8 to 10, wherein 2 at% < z" < 20 at%, preferably 4 at% < z" < 15 at%, and more preferably 5 at% < z" < 10 at%, relative to M".

12. The positive electrode active material blend according to any one of preceding claims 8 to 11, wherein D" comprises Nb, wherein 0 at% < a" < 4 at%, preferably 0.2 at% < a" < 3.5 at%, and more preferably 0.3 at% < a" < 3 at%, relative to M".

13. A method for preparing a positive electrode active material blend, preferably a positive electrode active material blend according to any one of preceding claims 1 to 12, comprising: a. For obtaining a first positive electrode active material powder: a.l providing a starting material comprising a Li source and a transition metal composite precursor; a.2 mixing the starting material to obtain a first mixture; a.3 heating the first mixture at a temperature between 650°C and 1000°C to obtain a heated material; a.4 providing a first intermediate material comprising the heated material; a.5 milling the first intermediate material to obtain a milled material; a.6 providing a second intermediate material comprising the milled material and a D-containing compound; a.7 mixing the second intermediate material to obtain a second mixture; and a.8 heating the second mixture at a temperature between 250°C and 500°C so as to obtain a first positive electrode active material powder. b. For obtaining a second positive electrode active material powder:b.l providing a second starting material comprising a Li source and a second transition metal composite precursor; b.2 mixing the starting material to obtain a third mixture; b.3 heating the third mixture at a temperature between 650°C and 1000°C to obtain a second heated material; b.4 grinding and sieving the second heated material so as to obtain a second positive electrode active material powder; c. mixing the first and second positive electrode active material powders, so as to obtain the positive electrode active material blend.

14. A solid state battery comprising the positive electrode active material according to any one of claims 1 to 12.

15. Use of the battery according to claim 14 in a portable electronic device, in a portable computer, in a tablet, in a mobile phone, in a power tool, in an energy storage system, in an uninterruptible power supply, in an electric vehicle, or in a hybrid electric vehicle.

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