Coated positive electrode material

Abstract

The present invention relates to a coated positive electrode active material, having a composition comprising Li, M, and O, wherein M comprises: Ni in a content x, wherein 40 at% ≤ x < 100 at%, relative to M; Mn in a content y, wherein 0 at% < y ≤ 35 at%; Co in a content z, wherein 0 at% < z ≤ 30 at%; D in a content d, wherein 0.0 at% ≤ a d ≤ 2 5.0 at%, wherein D is at least one element selected from Al, B, Co, Cu, Mn, Mo, Sr, Ti, V, W, Y, Zn and Zr; and coating element Si in a content b, wherein 0.000 at% < b ≤ 2.000 at%, and coating element P in a content c, wherein 0.000 at% < c ≤ 2.000 at%; and having a content SiXPS such that the ratio SiXPS / b ranges from 90 to 340, and having a content PXPS such that the ratio PXPS / c ranges from 45 to 250, wherein PXPS and SiXPS are respectively contents of P and Si in at% relative to M measured by X-ray Photoelectron Spectroscopy XPS.

Description

DescriptionTitleCOATED POSITIVE ELECTRODE MATERIALTechnical Field

[0001] The present disclosure concerns a coated positive electrode active material, in particular for solid state secondary batteries and a method for making the same.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. One of the drawbacks of solid state batteries is the appearance of polarization, where the charge voltage is higher than the discharge voltage.Summary

[0004] The present disclosure concerns a coated positive electrode active material, having a composition comprising Li, M, and O, wherein M comprises:i. Ni in a content x, wherein 40 at%x < 100 at%, relative to M; ii. Mn in a content y, wherein 0 at% < y35 at%, relative to M;iii. Co in a content z, wherein 0 at% < z30 at%, relative to M;iv. D in a content d, wherein 0.00 at%5.0 at%, relative to M, wherein D is at least one element selected from Al, Zr, B, W, Sr, Sb, Ti, Ba, Ca, Cr, F, Fe, Mg, Mo, Y, Zn, and S; andv. coating element Si in a content b, wherein 0.000 at% < b2.000 at%, relative to M,vi. coating element P in a content c, wherein 0.000 at% < c2.000 at%, relative to M;wherein x, y, z, d, b, c are measured by ICP-OES and x+y+z+b+c+d is 100 at%. andb. having a content Si XPS such that the ratio Sixps / b ranges from 90 to 340, wherein Sixps is a content of Si in at% relative to M measured by X-ray Photoelectron Spectroscopy (XPS);c. having a content PXPS such that the ratio PXPS / C ranges from 45 to 250, wherein PXPS is a content of P in at% relative to M measured by X-ray Photoelectron Spectroscopy (XPS);

[0005] It was surprisingly found that in a secondary battery, the coated positive electrode active material of the present disclosure may lead to increased first-cycle charge capacity CQ1, increased first-cycle discharge capacity DQ1, increased cell efficiency, and / or decreased polarization value CV1-DV1.

[0006] The present disclosure further concerns a method for preparing a coated positive electrode active material comprising:a. providing a coating material consisting ofi. a Si precursorii. a P precursor, wherein the P precursor is selected from a water-soluble P source, in particular from triethylphosphate, phosphorus pentoxide, phosphoric acid H3PO4, and ammonium phosphate ;andiii. a Li precursoriv. wherein the Si, P and Li precursors are optionally dissolved and / or suspended in a solventb. providing a positive electrode active material source powder, having a composition comprising Li, M’, and O, wherein M’ comprises:i. Ni in a content x’, wherein 40 at% < x’ < 100 at%, relative to M’; ii. Mn in a content y’, wherein 0 at% < y’ < 35 at%, relative to M’; iii. Co in a content z’, wherein 0 at% < z’ < 30 at%, relative to M’;iv. D’ in a content d’, wherein 0.00 at% < d’ < 5.0 at%, relative to M’, wherein D’ is at least one element selected from Al, Zr, B, W, Sr, Sb, Ti, Ba, Ca, Cr, F, Fe, Mg, Mo, Y, , Zn, and S,wherein x’, y’, z’, d’ are measured by ICP-OES;c. mixing the coating material and the positive electrode active material source powder so as to obtain a first mixture;d. heating the first mixture up to a temperature T, wherein 150°C < T <700 °C ; e. sieving or filtering the first mixture so as to separate the first slurry’s solids and liquid;f. drying the first mixture’s solids,so as to obtain the coated positive electrode active material

[0007] The inventors have found that the coated positive electrode active material obtained by the method of the present disclosure may lead to secondary batteries having increased first- cycle charge capacity CQ1, increased first-cycle discharge capacity DQ1, increased cell efficiency, and / or decreased polarization value CV1-DV1.

[0008] It is understood that the first mixture is a mixture of solids and a liquid, in other words a slurry, and may alternately be designated first slurry.Detailed disclosure

[0009] 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. 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.

[0010] “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.

[0011] "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.

[0012] “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.

[0013] As used herein, a range of values “from X to Y” and “between X and Y” include the endpoints of X and Y.

[0014] “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.

[0015] In an embodiment of the coated positive electrode active material of the present disclosure, 70 at% < x <90 at%, more preferably 80 at% < x < 90 at%, 82 at% < x < 90 at% relative to M. Without wishing to be bound by any theory, lesser amounts of Ni may lead to insufficient capacity and / or energy density in a battery.

[0016] In an embodiment of the coated positive electrode active material of the present disclosure, wherein 2 at% < y < 35 at%, preferably 4 at% < y < 30 at%, and more preferably 5 at% < y < 10 at%, relative to M. Without wishing to be bound by any theory, excessive amounts of Mn may lead to decreased structural battery stability resulting in poor cycling stability.

[0017] In an embodiment of the coated positive electrode active material of the present disclosure, 2 at% < z < 30 at%, preferably 4 at% < z < 20 at%, and more preferably 5 at% < z < 15 at%, relative to M. Without wishing to be bound by any theory, excessive amounts of Co leads to high costs and / or may promote side reactions with certain electrolytes.

[0018] In an embodiment of the coated positive electrode active material of the present disclosure, D is at least one element selected from the group consisting of Al, Sr, Zr, B and W.

[0019] In an embodiment of the coated positive electrode active material of the present disclosure, d is at least 0.05 at%, advantageously at least 0.10 at%, at least 0.15 at%, or even at least 0.20 at%.

[0020] In an embodiment of the coated positive electrode active material of the present disclosure, d is at most 4.0 at%, advantageously at most 3.5 at% or less, at most 3.0 at%, or even at most 2.5 at%.

[0021] In an embodiment of the coated positive electrode active material of the present disclosure, b is at least 0.005 at%, at least 0.010 at%, at least 0.015 at%, at least 0.020 at%, or even at least 0.025 at%.

[0022] In an embodiment of the coated positive electrode active material of the present disclosure, b is at most 1.000 at%, at most 0.700 at%, at most 0.500 at%, or even at most 0.400 at%.

[0023] In an embodiment of the coated positive electrode active material of the present disclosure, c is at least 0.005 at%, at least 0.010 at%, at least 0.015 at%, at least 0.020 at%, or even at least 0.025 at%.

[0024] In an embodiment of the coated positive electrode active material of the present disclosure, c is at most 1.700 at%, at most 1.400 at%, at most 1.000 at%, at most 0.700 at%, at most 0.500 at%, or even at most 0.400 at%.

[0025] In an embodiment of the coated positive electrode active material of the present disclosure, the ratio Sixps / b ranges from 100 to 330, from 110 to 320, or from 120 to 310.

[0026] In an embodiment of the coated positive electrode active material of the present disclosure, the ratio PXPS / C ranges from 55 to 240, from 65 to 230, or from 75 to 220.

[0027] In an embodiment of the coated positive electrode active material of the present disclosure, Sixps ranges from 5 to 50 at%.

[0028] In an embodiment of the coated positive electrode active material of the present disclosure, PXPS ranges from 5 to 50 at%.

[0029] In an embodiment of the coated positive electrode active material of the present disclosure, b / c ranges from 0.2 to 5.0, advantageously from 0.3 to 4.0, from 0.4 to 3.5, from 0.5 to 3, or even from 0.6 to 2.5.

[0030] In an embodiment of the coated positive electrode active material of the present disclosure, the Li / M molar ratio ranges from 0.9 to 1.1.

[0031] In an embodiment of the coated positive electrode active material of the present disclosure, it has a PSD D50 value ranging from 0.5 pm to 10 pm.

[0032] In an embodiment of the coated positive electrode active material of the present disclosure, it comprises single primary particles and / or secondary particles comprising 2 or more secondary particles. The number of primary particles constituting a secondary particle may be determined by counting the primary particles observed in a Scanning Electron Microscope (SEM) image at a magnification of 2000 from a top view, where the whole shape of the secondary particle is taken. 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.

[0033] In an embodiment of the present disclosure, the coated positive electrode active material is monolithic, that is it comprises single primary particles and / or secondary particles comprising at most twenty primary particles, preferably comprising at most 4 primary particles. Here within, “Monolithic” refers to particles, wherein each of the particles consists of at least one primary particle and at most twenty primary particles.

[0034] In an embodiment of the present disclosure, the coated positive electrode active material comprises secondary particles consisting of more than 20 primary particles. It this case it is not considered to be a monolithic material.

[0035] In an embodiment of the method of the present disclosure, the coated positive electrode active material is a coated positive electrode active material according to any embodiment or combination of embodiments of the present disclosure.

[0036] In an embodiment of the method of the present disclosure, the solvent is selected from one or more of H2O, ethanol, propanol, iso-propanol, and butanol.

[0037] In an embodiment of the method of the present disclosure, the Si precursor is selected from SiC>2, tetra-ethyl orthosilicate (TEOS), silicon sulfide, and silicon nitride.

[0038] In an embodiment of the method of the present disclosure, the Li precursor is selected from Lithium hydroxide LiOH, Lithium ethoxide, lithium acetate, lithium sulfate, lithium chloride and lithium carbonate.

[0039] In an embodiment of the method of the present invention lithium phosphate U3PO4 is used as P precursor and as Li precursors. Additional P and / or Li precursors may be used in combination with U3PO4.

[0040] In an embodiment of the method of the present disclosure, x’+y’+z’+d’ is 100 at%.

[0041] In an embodiment of the method of the present disclosure, 55 at% < x’ < 95 at%, preferably 65 at% < x’ < 95 at%, and more preferably 70 at% < x’ <95 at%, more preferably 80 at% < x’ < 95 at%, 82 at% < x’ < 90 at% relative to M’.

[0042] In an embodiment of the method of the present disclosure, wherein 2 at% < y’ < 35 at%, preferably 4 at% < y’ < 30 at%, and more preferably 5 at% < y’ < 10 at%, relative to M’.

[0043] In an embodiment of the method of the present disclosure, 2 at% < z’ < 30 at%, preferably 4 at% < z’ < 20 at%, and more preferably 5 at% < z’ < 15 at%, relative to M’.

[0044] In an embodiment of the method of the present disclosure, D’ is at least one element selected from of Al, Sr, Zr, B and W.

[0045] In an embodiment of the method of the present disclosure, d’ is at least 0.05 at%, advantageously at least 0.10 at%, at least 0.15 at%, or even at least 0.20 at%.

[0046] In an embodiment of the method of the present disclosure, d’ is at most 4.0 at%, advantageously at most 3.5 at% or less, at most 3.0 at%, or even at most 2.5 at%.

[0047] In an embodiment of the method of the present disclosure, the Li / M ’ molar ratio of the positive electrode active material source powder ranges from 0.9 to 1.1.

[0048] In an embodiment of the method of the present disclosure, PSD D50 value of the positive electrode active material source powder ranges from 0.5 pm to 10 pm.

[0049] In an embodiment of the method of the present disclosure, the coating material comprises Si and P in a molar ratio of Si / P ranging from 0.2 to 5.0, advantageously from 0.3 to 4.0, from 0.4 to 3.5, from 0.5 to 3, or even from 0.6 to 2.5.

[0050] In an embodiment of the method of the present disclosure, the coating material comprises Li, Si and P in a molar ratio Li:Si:P of (3+t) : t : (1-t), wherein 0.3 < t < 0.9.

[0051] In an embodiment of the method of the present disclosure, mixing the coating material and the positive electrode active material source powder so as to obtain a first mixture comprising a weight ratio of the sum of Si precursor, P precursor, and Li precursor to the positive electrode active material source powder of between 1 and 20%.

[0052] In an embodiment of the method of the present disclosure, in step d. 200°C < T <350 °C, alternately 200°C < T <250 °C or 250°C < T <350 °C.

[0053] In an embodiment of the method of the present disclosure, the first mixture may be kept at temperature T for a duration of 3h to 15h, advantageously of 5h to 7h.

[0054] The present disclosure further concerns a battery comprising the coated positive electrode active material according to any embodiment or combination of embodiments of the present disclosure.

[0055] The battery of the present disclosure may in particular be a solid state secondary battery, in particular a lithium ion solid state secondary battery.

[0056] A lithium secondary battery generally includes a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and the negative electrode include an active material capable of intercalation and deintercalation of lithium ions.

[0057] The battery of the present disclosure may comprise a solid electrolyte selected from a sulfide solid electrolyte and an oxide solid electrolyte.

[0058] The present disclosure further concerns the use of the battery of the present disclosure in an electric vehicle or in a hybrid electric vehicle.EXPERIMENTAL ANALYSIS USED IN THE EXAMPLES AND THE COMPARATIVE EXAMPLE

[0059] The following analysis methods are used in the Examples and the Comparative Example. A) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) measurement

[0060] The amount of Ni, Mn, and Co 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

[0061] 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 Aero S unit. A quantity of solid powder is introduced into a venturi with flowing compressed air (~3 atm) to break up agglomerates and introduce a well dispersed sample stream into the detection unit. D50 is defined as the particle size at 50% of the cumulative volume% distributions.C) X-ray Photoelectron Spectroscopy (XPS)

[0062] In the present disclosure, 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.Therefore, all elements measured by XPS are contained in the surface layer.

[0063] For the surface analysis of positive electrode active material powder particles, XPS measurement is carried out using a Thermo K-a+ spectrometer. Monochromatic Al Ka radiation (hu=1486.6 eV) is used with a spot size of 400 mm and measurement angle of 45 °. A wide survey scan to identify elements present at the surface is conducted at 200 eV pass energy. C1s 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.

[0064] 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 1a. Line shape GL(30) is the Gaussian / Lorentzian product formula with 70%Gaussian line and 30% Lorentzian line. Line shape LA(a,p,m) is an asymmetric line-shape, wherein a and p define the spread of the tail on either side of the Lorentzian component and wherein m specifies the width of the Gaussian used to convolute the Lorentzian curve. Full width at half maximum (FWHM) are useful indicators of chemical state changes and physical influences. That is, broadening of a peak may indicate: a change in the number of chemical bonds contributing to a peak shape, a change in the sample condition (x-ray damage) and / or differential charging of the surface (localized differences in the charge state of the surface)

[0065] Table 1a. XPS fitting parameter for Ni2p, Mn2p, Co2p, and Zr3d.

[0066] For Ni peaks, constraints are set for each defined peak according to Table 1b.

[0067] Table 1b. XPS fitting constraints for Ni peak fitting.

[0068] The Si and P surface contents as determined by XPS is expressed as atomic fractions of Si and P respectively in the surface layer of the particles divided by the total contents of Ni, Mn, Co, Si, P and optional dopants in said surface layer. It is calculated as following: atomic ratio oatomic ratio <D) Sulfide solid-state rechargeable cell testD1) Sulfide solid-state rechargeable cell preparationD1.1) Positive electrode preparation

[0069] For the preparation of a positive electrode, a slurry contains positive electrode active material powder, Li-P-S based solid electrolyte, carbon (Super-P, Timcal), and binder (RC- 10, Arkema) - with a formulation of 64.0 : 30.0 : 3.0 : 3.0 by weight - in butyl acetate solvent is mixed in Ar-filled glove box. The slurry is casted on one side of an aluminum foil followed by drying the slurry coated foil in a vacuum oven to obtain a positive electrode. The obtained positive electrode is punched with a diameter of 10 mm wherein the active material loading amount is around 4 mg / cm2.D1.2) Negative electrode preparation

[0070] For the preparation of a negative electrode, Li foil (diameter 3 mm, thickness 100 pm) is placed centered on the top of In foil (diameter 9 mm, thickness 100 pm) and pressed to form Li-ln alloy negative electrode.D1.3) Separator preparation

[0071] For the preparation of a separator which also has a function of the solid electrolyte in a battery, the Li-P-S based solid electrolyte is pelletized with a pressure of 250 MPa to obtain 100 pm pellet thickness.D1.4) Cell assembling

[0072] A sulfide solid-state rechargeable battery is assembled in an Ar-filled glovebox with such order from bottom to top: positive electrode comprising Al current collector with the coated part on the top - separator - negative electrode with Li side on the top - Cu current collector. The stacked components are pressed together with a pressure of 250 MPa and placed in an external cage to prevent air exposure.D2) Testing method

[0073] The testing method is a conventional “constant cut-off voltage” test. Each cell is cycled at 60 °C using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo).

[0074] The schedule uses a 1C current definition of 160 mA / g. The initial charge capacity (CQ1) and discharge capacity (DQ1) are measured in constant current mode (CC) at C rate of 0.1C in voltage range from 4.3 V to 2.5 V (Li / Li+) or from 3.7 V to 1.9 V (ln-Li / Li+). The efficiency (%) of the irreversible capacity is obtained according to an equation below:100(%).

[0075] The difference between the average voltage of the initial charge (CV1) and the average voltage of the initial discharge (DV1) is used to determine the amount of polarization of the positive electrode. To calculate CV1, a capacity in terms of power, in Watt-hours (Wh), is divided with CQ1. The capacity in terms of power of the discharge in the first cycle (Wei) is calculated from the area beneath the plotted graph of voltage (V) versus capacity (mAh / g). DV1 is calculated by dividing the capacity in terms of power of the discharge in the first cycle (WDI) with DQ1:Polarization value (m7) = CV1 (mV) — DV1 (mV).E) Coin Cell TestingE-1) Coin Cell Preparation

[0076] For the preparation of a , a slurry that contains a cathode active material powder, a conductor (Li-435, ANP), a binder (KF#9700, Kureha), with a formulation of 96.22:1.98:1.8 by weight - in a solvent (NMP, Mitsubishi) is prepared by a high-speed homogenizer. The homogenized slurry is spread on one side of an aluminum foil using a doctor blade coater with a 170 pm gap. The slurry coated foil is dried in an oven at 120°C and then pressed using a calendaring tool. Then it is dried again in a vacuum oven to completely remove the remaining solvent in the electrode film. A coin cell is assembled in an argon-filled glovebox. A separator (Celgard 2320) is located between a cathode and a piece of lithium foil used as an anode. 1M LiPFe in EC (ethylene carbonate) / DMC (dimethyl carbonate) (1:2) + FEC (fluoroethylene carbonate) is used as electrolyte and is dropped between separator and electrodes. Then, the coin cell is completely sealed to prevent leakage of the electrolyte. E-2) Testing Method

[0077] The testing method is a conventional “constant cut-off voltage” test. The conventional coin cell test in the present invention follows the schedule shown in Table 1. Each cell is cycled at 25°C using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo).

[0078] The schedule uses a 1C current definition of 200mA / g in the 4.3V to 2.5V / U metal window range. The efficiency (%) of the irreversible capacity is obtained according to an equation below:Efficiency (%) = — x 100(%).

[0079] The difference between the average voltage of the initial charge (CV1) and the average voltage of the initial discharge (DV1) is used to determine the amount of polarization of the positive electrode. To calculate CV1, a capacity in terms of power, in Watt-hours (Wh), is divided with CQ1. The capacity in terms of power of the discharge in the first cycle (Wei) is calculated from the area beneath the plotted graph of voltage (V) versus capacity (mAh / g). DV1 is calculated by dividing the capacity in terms of power of the discharge in the first cycle (WDI) with DQ1:Polarization value (m7) = CV1 (mV) — DV1 (mV).

[0080] Table 2. Cycling schedule for Coin cell testing methodEXAMPLES

[0081] The present invention is further illustrated in the following examples.

[0082] Two different positive electrode active material source powders were used, CAM1 and CAM2.

[0083] Table 3: Composition of CAM 1 and CAM2Positive electrode active material powder (CAM1)

[0084] A positive electrode active material CAM1, or positive electrode active material source, was obtained through following steps:a. Mixing: a precursor having transition metal composition as Ni0.85Mn0.07Co0.08 in hydroxide or oxyhydroxide form was mixed homogeneously with LiOH, wherein the molar ratio of Li to total amount of Ni, Mn, and Co is 1.01 , to prepare a first mixture. b. Heating: the first mixture was heated at 765 °C for 10 hours followed by cooling, grinding, and sieving to prepare a positive electrode active material CAM1. The resulting CAM 1 is not a monolithic material, but comprises secondary particles comprising a plurality of primary particles.Positive electrode active material powder (CAM2)

[0085] A positive electrode active material CAM2, or positive electrode active material source, was obtained through following steps:a. First mixing: a precursor having transition metal composition as Ni0.92Mn0.07Co0.08 in hydroxide or oxyhydroxide form was mixed homogeneously with LiOH and ZrO2 to prepare a first mixture, wherein 0.125 at% Zr relative to total amount of Ni, Mn, and Co was added and a molar ratio of Li to total amount of Ni, Mn, and Co is 1.00. b. First heating: the first mixture was heated at 835 °C for 6 hours in an oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material.c. Wet milling: the first heated material was bead milled in an aqueous solution containing COSO4 followed by filtering and drying to prepare a milled material having D50 of between 2.9 pm and 3.3 pm, wherein 0.5 at% Co relative to total amount of Ni, Mn, and Co in the first heated material was contained in the aqueous solution.d. Second mixing: the milled material was mixed homogeneously with LiOH and CO3O4 to prepare a second mixture, wherein 3 at% Co relative to total amount of Ni, Mn, and Co in the milled material was added and a molar ratio of Li to total amount of Ni, Mn, and Co of the second mixture was 1.00.e. Second heating: the second mixture was heated at 720 °C for 8 hours in an oxygen atmosphere followed by cooling, grinding, and sieving so as to obtain a positive electrode active material CAM2. The resulting CAM 2 is a monolithic material. Comparative Example 1 (CEX1)

[0086] Unmodified CAM1 was used as CEX1.Example 1.1 (EX1.1)

[0087] A positive electrode active material EX1.1 was obtained through following steps:a. Mixing: CAM1 was mixed with an aqueous solution containing LiOH, tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 700 ppm Si and 1182 ppm P relative to weight of CAM1 were contained in the aqueous solution and wherein a molar ratio of Li relative to Si is 8.5.b. Heating: the mixture was heated at 250 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX1.1. Example 1.2 (EX1.2)

[0088] A positive electrode active material EX1.2 was obtained through following steps:a. Mixing: CAM1 was mixed with an aqueous solution containing LiOH, tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 1225 ppm Si and 591 ppm P relative to weight of CAM1 were contained in the aqueous solution and wherein a molar ratio of Li relative to Si is 5.3.b. Heating: the mixture was heated at 250 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX1.2. Example 2.1 (EX2.1)

[0089] A positive electrode active material EX2.1 was obtained through following steps:a. Mixing: CAM1 was mixed with an aqueous solution containing LiOH, tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 700 ppm Si and 1182 ppm P relative to weight of CAM1 were contained in the aqueous solution and wherein a molar ratio of Li relative to Si is 8.5.b. Heating: the mixture was heated at 350 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX2.1. Example 2.2 (EX2.2)

[0090] A positive electrode active material EX2.2 was obtained through following steps:a. Mixing: CAM1 was mixed with an aqueous solution containing LiOH, tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 1225 ppm Si and 591 ppm P relative to weight of CAM1 were contained in the aqueous solution and wherein a molar ratio of Li relative to Si is 5.3.b. Heating: the mixture was heated at 350 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX2.2. Comparative Example 2.1 (CEX2.1)

[0091] A positive electrode active material CEX2.1 was obtained through following steps:a. Mixing: a precursor having transition metal composition as Ni0.85Mn0.07Co0.08 in hydroxide or oxyhydroxide form was mixed homogeneously with LiOH, SiC>2, and U3PO4 to prepare a mixture, wherein 700 ppm Si and 1182 ppm P relative to weight of the precursor were added and wherein a molar ratio of Li relative to Si is 8.5.b. Heating: the first mixture was heated at 785 °C for 10 hours in an oxygen atmosphere followed by cooling, grinding, and sieving so as to obtain a positive electrode active material CEX2.1.Comparative Example 2.2 (CEX2.2)

[0092] A positive electrode active material CEX2.2 was obtained through following steps:a. Mixing: a precursor having transition metal composition as Ni0.85Mn0.07Co0.08 in hydroxide or oxyhydroxide form was mixed homogeneously with LiOH, SiO2, and U3PO4 to prepare a mixture, wherein 1225 ppm Si and 591 ppm P relative to weight of the precursor were added and wherein a molar ratio of Li relative to Si is 5.3.b. Heating: the first mixture was heated at 785 °C for 10 hours in an oxygen atmosphere followed by cooling, grinding, and sieving so as to obtain a positive electrode active material CEX2.2.Comparative Example 3 (CEX3)

[0093] A positive electrode active material CEX3 was obtained through following steps:

[0094] Mixing: CAM1 was mixed with an aqueous solution containing LiOH and triethyl phosphate followed by evaporating water to prepare a mixture, wherein 1969 ppm P relative to the amount of CAM1 were contained in the aqueous solution and wherein a molar ratio of Li relative to P is 3.0.a. Heating: the mixture was heated at 800 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material CEX3. Example 3.1 (EX3.1)

[0095] A positive electrode active material EX3.1 was obtained through following steps:a. Mixing: CAM2 was mixed with an aqueous solution containing tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 150 ppm Si and 253 ppm P relative to weight of CAM2 were contained in the aqueous solution. b. Heating: the mixture was heated at 250 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX3.1. Example 3.2 (EX3.2)

[0096] A positive electrode active material EX3.2 was obtained through following steps:a. Mixing: CAM2 was mixed with an aqueous solution containing tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 225 ppm Si and 169 ppm P relative to weight of CAM2 were contained in the aqueous solution. b. Heating: the mixture was heated at 250 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX3.2. Example 4 (EX4)

[0097] A positive electrode active material EX4 was obtained through following steps:a. Mixing: CAM2 was mixed with an aqueous solution containing tetraethyl orthosilicate, and triethyl phosphate to prepare a mixture, wherein 300 ppm Si and 506 ppm P relative to weight of CAM2 were contained in the aqueous solution. b. Heating: the mixture was heated at 250 °C for 6 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material EX4. Comparative Example 4.1 (CEX4.1)

[0098] A positive electrode active material CEX4.1 was obtained through following steps:a. First mixing: a precursor having transition metal composition as Ni0.92Mn0.07Co0.08 in hydroxide or oxyhydroxide form having D50 between 3.0 pm and 3.5 pm was mixed homogeneously with LiOH, SiC>2, and U3PO4 to prepare a first mixture, wherein 150 ppm Si and 253 ppm P relative to weight of the precursor were added and a molar ratio of Li to total amount of Ni, Mn, and Co is 1.00.b. First heating: the first mixture was heated at 835 °C for 6 hours in an oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material.c. Second mixing: the first heated material was mixed with an aqueous solution containing 3.5 mol% Co(NC>3)2 relative to total amount of Ni, Mn, and Co in the first heated material followed by filtering and drying to prepare a second mixture.d. Second heating: the second mixture was heated at 700 °C for 15 hours followed by cooling, grinding, and sieving so as to obtain a positive electrode active material CEX4.1Comparative Example 4.2 (CEX4.2)

[0099] A positive electrode active material CEX4.2 was obtained following the same process of preparing CEX4.1 except that 225 ppm Si and 169 ppm P were added in step a.Comparative Example 5 (CEX5)

[0100] Unmodified CAM2 was used as CEX5.Example 5 (EX5)

[0101] A positive electrode active material EX5 was obtained following the same process of preparing EX3.1 except that the mixture was heated at 350 °C for 6 hours followed by cooling, grinding, and sieving in step b.

[0102] Table 4: compositional data

[0103] Table 5: battery performance - sulfide SSB

[0104] Table 6: battery performance - coin cell

[0105] As can be seen from the Table 5 above, CEX1 which is prepared using a positive electrode active material without Si and without P, the polarization value is too high at 88.7mV. In comparison with CEX1, invention examples EX1.1, EX1.2, EX2.1 and EX2.2 show smaller polarization values and in addition increased efficiencies.

[0106] Comparative examples CEX2.1 and CEX2.2, which are prepared using a positive electrode active material having low Sixps / b ratios as well as low PXPS / C ratios, show high polarization values as well as low efficiency values. Comparative example CEX2, without Si and having a low PXPS / C ratio has a low efficiency as well.

[0107] In Table 5, Comparative examples CEX4.1 and CEX4.2, prepared using a positive electrode active material having a Sixps / b ratio in the desired range, but a low PXPS / C ratio also show low efficiency as well as high polarization values. In comparison, invention examples EX3.1, EX3.2, and EX4 show low polarization values as well as high efficiencies.

[0108] As can be seen in Table 6, Even from coin cell testing with liquid electrolyte, example EX5 shows higher charge and discharge capacity and lower polarization value compared to CEX5, wherein EX5 was prepared using a positive electrode active material with Si and P.

[0109] This thus shows that coated positive electrode active material of the present disclosure leads to batteries having lower polarization values and higher efficiencies.

Claims

Claims

1. Coated positive electrode active material, having a composition comprising Li, M, and O, wherein M consists :i. Ni in a content x, wherein 65 at% < x < 92 at%, relative to M; ii. Mn in a content y, wherein 0 at% < y35 at%, relative to M;iii. Co in a content z, wherein 0 at% < z30 at%, relative to M; iv. D in a content d, wherein 0.00 at%5.0 at%, relative to M, wherein D is at least one element selected from Al, B, Co, Cu, Mn, Mo, Sr, Ti, W, Y, Zn and Zr; andv. coating element Si in a content b, wherein 0.000 at% < b1.400 at%, relative to M,vi. coating element P in a content c, wherein 0.000 at% < c2.000 at%, relative to M;wherein x, y, z, b, c and dare measured by ICP-OES and x+y+z+b+c+d is 100 at%; andb. having a content Si XPS such that the ratio Sixps / b ranges from 90 to 340, wherein Sixps is a content of Si in at% relative to M measured by X-ray Photoelectron Spectroscopy (XPS);c. having a content PXPS such that the ratio PXPS / C ranges from 45 to 250, wherein PXPS is a content of P in at% relative to M measured by X-ray Photoelectron Spectroscopy (XPS).

2. Coated positive electrode active material according to claim 1, wherein b / c ranges from 0.2 to 5.0.

3. Coated positive electrode active material according to claim 1 or claim 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. Coated positive electrode active material according to any one preceding claim wherein 2 at% < y < 35 at%, preferably 4 at% < y < 30 at%, and more preferably 5 at% < y < 10 at%, relative to M.

5. Coated positive electrode active material according to any one preceding claim 2 at% < z < 30 at%, preferably 4 at% < z < 20 at%, and more preferably 5 at% < z < 15 at%, relative to M.

6. Coated positive electrode active material according to any one preceding claim wherein d is at least 0.05 at% and / or at most 4.0 at%.

7. Coated positive electrode active material according to any one preceding claim wherein the ratio Sixps / b ranges 100 to 330.

8. Coated positive electrode active material according to any one preceding claim wherein the ratio PXPS / C ranges from 55 to 240.

9. Method for preparing a coated positive electrode active material comprising: a. providing a coating material consisting ofi. a Si precursorii. a P precursor, wherein the P precursor is selected from a water-soluble P source, in particular from triethylphosphate, phosphorus pentoxide, phosphoric acid H3PO4, and ammonium phosphate; and iii. a Li precursoriv. wherein the Si, P and Li precursors are optionally dissolved and / or suspended in a solventb. providing a positive electrode active material source powder, having a composition comprising Li, M’, and O, wherein M’ comprises:i. Ni in a content x’, wherein 40 at% < x’ < 100 at%, relative to M’;ii. Mn in a content y’, wherein 0 at% < y’ < 35 at%, relative to M’;iii. Co in a content z’, wherein 0 at% < z’ < 30 at%, relative to M’;iv. D’ in a content d’, wherein 0.00 at% < d’ < 5.0 at%, relative to M’, wherein D’ is at least one element selected from Al, Zr, B, W, Sr, Sb, Ti, Ba, Ca, Cr, F, Fe, Mg, Mo, Y, Zn, and S,wherein x’, y’, z’, d’ are measured by ICP-OES;c. mixing the coating material and the positive electrode active material source powder so as to obtain a first mixture;d. heating the first mixture up to a temperature T, wherein 150°C < T <700 °C;e. sieving or filtering the heated first mixture so as to separate the first mixture’s solids and liquid;f. drying the first mixture’s solids,so as to obtain the coated positive electrode active material.

10. Method according to claim 9 wherein the coated positive electrode active material is a coated positive electrode active material according to any one of claims 1 to 8.

11. Method according to claim 9 wherein the solvent is selected from H2O, ethanol, propanol, iso-propanol, and butanol.

12. Method according to any one of claims 9 to 10 wherein the Si precursor is selected from SiC>2, tetra-ethyl orthosilicate , silicon sulfide, and silicon nitride.

13. Method according to any one of claims 9 to 12 wherein the Li precursor is selected from Lithium ethoxide, lithium hydroxide LiOH , lithium acetate, lithium sulfate, lithium chloride, and / or lithium carbonate.

14. Battery comprising a coated positive electrode active material according to any one of claims 1 to 8.

15. Use of a according to claim 14 in an electric vehicle or in a hybrid electric vehicle.

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