WO2025233380A1

WO2025233380A1 - Method for preparing a positive electrode active material powder and a positive electrode active material powder

Info

Publication number: WO2025233380A1
Application number: PCT/EP2025/062441
Authority: WO
Inventors: Jihye Kim; Bingchao TAN; Woon-Hyoung RYU; KyoungMoon RYU; Song-Yi Han
Original assignee: Umicore NV SA
Current assignee: Umicore NV SA
Priority date: 2024-05-08
Filing date: 2025-05-07
Publication date: 2025-11-13
Anticipated expiration: 2026-11-08

Abstract

A method for preparing a positive electrode active material powder for lithium-ion rechargeable batteries, comprising: Step 1) mixing a Li source, a transition metal precursor, and a Zr-containing source to obtain a mixture; Step 2) heating the mixture at a temperature between 650 °C and 1100 °C to obtain a heated material; and Step 3) milling the heated material, wherein the transition metal precursor comprises Ni, optionally Co, and optionally Mn, and wherein the transition metal precursor has a D50 value of less than 5.0 μm, D50 being defined as a particle size at 50% of cumulative volume% distribution when measured by laser scattering method.

Description

METHOD FOR PREPARING A POSITIVE ELECTRODE ACTIVE MATERIAL POWDER AND A POSITIVE ELECTRODE ACTIVE MATERIAL POWDER

TECHNICAL FIELD AND BACKGROUND

The present invention relates to a method for preparing a positive electrode active material powder for lithium-ion rechargeable batteries, comprising milling a lithiated material.

The condition of milling a positive electrode active material powder can affect a particle size distribution ("PSD") of the positive electrode active material powder. It is well known in the art that the PSD of a positive electrode active material powder has an impact on the performance of a battery comprising the positive electrode active material powder. In particular, a positive electrode active material having a narrow PSD is advantageous to the battery performance.

However, it is difficult to obtain a positive electrode active material powder having a sufficiently narrow PSD only by milling. Accordingly, a method of further narrowing a PSD as compared to a PSD obtained only by milling is demanded.

It is a first object of the present invention to provide a method for preparing a positive electrode active material powder, the PSD of which is more uniform than the PSD obtained only by milling.

It is a second object of the present invention to provide a positive electrode active material powder prepared by one of said method according to the present invention.

It is a third object of the present invention to provide a positive electrode active material powder prepared by one of said method according to the present invention.

It is a fourth object of the present invention to provide a battery comprising said positive electrode active material powder according to the present invention.

It is a fifth object of the present invention to provide a use of said battery comprising said positive electrode active material powder according to the present invention.

SUMMARY OF THE INVENTION

The first object is achieved by providing a method for preparing a positive electrode active material powder for lithium-ion rechargeable batteries, comprising: Step 1) mixing a Li source, a transition metal composite precursor, and a Zr-containing compound to obtain a mixture;

Step 2) heating the mixture at a temperature between 650 °C and 1100 °C to obtain a heated material; and

Step 3) milling the heated material, wherein the transition metal composite precursor comprises Ni, optionally Co, and optionally Mn, and wherein D50 of the transition metal composite precursor is less than 5.0 pm, D50 being defined as a particle size at 50% of cumulative volume% distribution when measured by laser scattering method.

It is described in Zhang et al, Particuology 61, 2022, pp. 533-535 that the PSD determines the particle packing, polydispersity, and porosity of electrode materials, which directly affect the mass transfer of lithium ions during charging and discharging, as well as the final energy density of the batteries, and that a uniform PSD of the positive electrode active material powder is expected to have better electrochemical performance. The present inventors have found that the PSD of a positive electrode active material can be more narrowed if a Zr- containing compound is added to a mixture containing a transition metal composite precursor and a Li source, wherein the transition metal composite precursor having a D50 of less than 5.0 pm.

The second object is achieved by providing a positive electrode active material for lithium-ion rechargeable batteries prepared by the method, wherein the heated material in Step 3) is milled by jet milling.

The third object is achieved by providing a positive electrode active material for lithium-ion rechargeable batteries prepared by the method, wherein the heated material in Step 3) is milled by wet ball milling.

The fourth object is achieved by providing a battery comprising the positive electrode active material powder according to the present invention.

The fifth object is achieved by providing a use of the battery comprising the positive electrode active material powder according to the present invention.

DETAILED DESCRIPTION

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

Method for Manufacturing Positive Electrode Active Material Powder

In a first aspect, the present invention relates to a method of preparing a positive electrode active material powder for lithium-ion rechargeable batteries, comprising:

Step 1) mixing a Li source, a transition metal composite precursor, and a Zr-containing compound to obtain a mixture;

Step 3) milling the heated material, wherein the transition metal composite precursor comprises Ni, optionally Co, and optionally Mn, and wherein the transition metal composite precursor has a D50 value of less than 5.0 pm, D50 being defined as a particle size at 50% of cumulative volume% distribution when measured by laser scattering method as described in this specification.

The inventors of the present invention have found out that a span of a positive electrode active material powder is lowered if the positive electrode active material is prepared by the method according to the first aspect. That is, the span of a positive electrode active material powder prepared by the method, wherein the addition of a Zr-containing compound and the addition of a transition metal composite precursor having D50 of less than 5.0 pm are combined during Step 1), is much lowered than the span of a positive electrode active material powder prepared by a method, wherein one or none of the Zr-containing compound and the transition metal composite precursor having D50 of less than 5.0 pm is added during Step 1).

The span represents a particle size distribution ("PSD") of a positive electrode active material powder. As the span gets lower, the PSD gets narrower. The span is defined as (D90- D10)/D50, D10, D50 and D90 being defined as particle sizes at 10%, 50% and 90% of cumulative volume% distribution when measured by laser scattering method as described in this specification, respectively. The PSD determines the particle packing, polydispersity and porosity of a positive electrode active material powder. The lower span of a positive electrode active material powder results in better safety and cycle stability caused by homogeneous distribution of the positive electrode active material in a positive electrode. In addition, the lower span results in potentially higher energy density of a battery because it allows to design a battery electrode having a higher volumetric packing density. D99/D50 of a positive electrode active material powder is also lowered if the positive electrode active material powder is prepared by the method according to the first aspect. D99 is defined as a particle size at 99% of cumulative volume% distribution when measured by laser scattering method as described in this specification. D99 is a parameter to estimate the maximum particle size. The maximum particle size should be controlled to prevent ripping apart or breaking of current collector during electrode calendaring, which is called as "electrode biting effect." In order to reach a higher electrode density, it is preferable to maintain the ratio of D99 to D50 at a low value. Furthermore, a positive electrode active material powder having a low D99/D50 also has a low PSD, and thus, it results in better safety, cycle stability and potentially higher energy density of a battery.

In a preferred embodiment, the Zr-containing compound is at least one selected from the group consisting of zirconium oxide, zirconium hydroxide, and lithium zirconium oxide.

In a preferred embodiment, the Li source is LiOH and/or Li2COs, and preferably LiOH. Li2COs usually requires a high temperature to complete the synthesis of a positive electrode active material powder. This high temperature can damage the crystal structure of the positive electrode active material powder and change the oxidation state of Ni, leading to a poor performance of the battery. On the contrary, LiOH allows rapid and complete synthesis at lower temperature, resulting in a longer battery life cycle and enhanced safety features, and improving the throughput of the process.

In a preferred embodiment, the D50 value of the transition metal composite precursor is less than 4.5 pm, and preferably less than 4.0 pm.

In a preferred embodiment, the mixture in Step 2) is heated for 4 to 10 hours, preferably 5 to 9 hours, and more preferably 6 to 8 hours.

In a preferred embodiment, the mixture in Step 2) is heated in a single heating step for 4 to 10 hours, preferably in a single heating step for 5 to 9 hours, and more preferably in a single heating step for 6 to 8 hours. A single heating step reduces the heating time and improves the throughput of the overall process.

In a preferred embodiment, the temperature in Step 2) is between 700 °C and 1050 °C, preferably between 750 °C and 1000 °C, more preferably 800 °C and 980 °C.

In a preferred embodiment, the Zr-containing compound in Step 1) is added in a content of 0.05-0.50 mol%, preferably 0.10-0.45 mol%, and more preferably 0.15-0.40 mol%, with respect to the Zr-containing compound and the transition metal composite precursor. In a preferred embodiment, the transition metal composite precursor comprises particles comprising Li, Ml' and oxygen, wherein Ml' comprises:

Ni in a content xl, wherein 40.0 at% < xl < 98.0 at%, preferably 50.0 at% < xl < 95.0 at%, more preferably 55.0 at% < xl < 90.0 at%, still more preferably more preferably 60.0 at% < xl < 90.0 at%, relative to Ml';

Co in a content yl, wherein 0.0 at% < yl < 15.0 at%, preferably 1.0 at% < yl < 10.0 at%, more preferably 2.0 at% < yl < 8.0 at%, still more preferably 3.0 at% < yl < 7.0 at%, relative to Ml'; and

Mn in a content zl, wherein 0.0 at% < zl < 45.0 at%, preferably 5.0 at% < zl < 40.0 at%, more preferably 10.0 at% < zl < 38.0 at%, still more preferably 15.0 at% < zl < 35.0 at%, relative to Ml', wherein xl, yl, and zl are measured by ICP-OES as described in this specification, and wherein xl+yl+zl is 100.0 at%.

In the framework of the present invention, 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% 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 i^th element Ei, Eawi is a standard atomic weight (molecular weight) of said i^th element Ei, and n is an integer which represents the number of types of all elements included in the material.

In a preferred embodiment, the heated material in Step 3) is milled by jet milling.

Milling is the action of reducing the size of particles by a mechanical action. The mechanical action is submitting the particles to a stress. Some cracks will appear under the stress, and subsequently the particle will be broken into different parts.

Jet milling may achieve a size reduction by accelerating the product to be milled to give enough energy to the product and throwing the product either against a static target or against another flux of accelerated particles to break the product at the impact. Since a single pass through the apparatus of jet milling would create a very wide PSD, the apparatus of jet milling may be equipped with a classifier such that only particles below a target size should be allowed to leave the apparatus of jet milling while the other particles are recirculated, and thereby the PSD should be narrowed. The rotation speed of the classifier may range from 1000 rpm to 5000 rpm, preferably 2000 rpm to 4000 rpm, more preferably 2500 rpm to 3500 rpm. During jet milling, compressed gas is forced into a jet milling apparatus consisting of a short cylinder through nozzles tangent to the cylinder wall. The gas leaves the apparatus through a tube along the axis of the cylinder. A pressure of gas introduced into the apparatus of jet milling may range from 0.10 MPa to 0.40 MPa, preferably from 0.15 MPa to 0.35 MPa, more preferably from 0.20 MPa to 0.30 MPa.

In a preferred embodiment, the heated material in Step 3) is milled by wet ball milling.

Wet ball milling is for milling solids in wet phase by introducing a liquid. It is basically a ball milling, wherein a rotating vessel filled with a grinding media as well as a product is rotated such that the grinding media should impact and/or apply a shear stress to the product. The apparatus of wet ball milling may be equipped with an agitator, which moves to make the grinding media impact or friction the particles to be milled.

In a preferred embodiment, the heated material in Step 3) of the method according to the first aspect of the present invention is mixed with a solution comprising or consisting of deionized water. The grinding media may be at least one selected from the group consisting of ZrO?, AI2O3 and tungsten carbide beads. The grinding media may have a diameter between 0.5 mm and 20.0 mm, preferably 5.0 mm and 15.0 mm, more preferably between 8.0 mm to 12.0 mm.

Positive Electrode Active Material Powder

In a second aspect, the present invention relates to a positive electrode active material powder for lithium-ion rechargeable batteries prepared by the method according to the first aspect, wherein the heated material in Step 3) is milled by jet milling, and wherein the positive electrode active material powder has a span being lower than or equal to 1.30, preferably 1.25, and more preferably 1.20.

The inventors of the present invention have found out that the span of a positive electrode active material may be lower than or equal to 1.30, preferably 1.25, more preferably 1.20, and higher than or equal to 0.90, preferably 0.95, more preferably 1.00, when the positive electrode active material is prepared by the method according to the first aspect, and when the heated material in Step 3) of the first aspect is milled by jet milling. In a preferred embodiment, D50 of the positive electrode active material powder ranges: 2.0 pm < D50 < 10.0 pm, preferably 2.3 pm < D50 < 8.0 pm, and more preferably 2.5 pm < D50 < 6.0 pm.

In a preferred embodiment, the positive electrode active material powder has D99/D50 being lower than or equal to 2.70, preferably 2.60, more preferably 2.50, and most preferably 2.40.

In a preferred embodiment, the positive electrode active material powder comprises particles comprising Li, M2', and oxygen, wherein M2' comprises:

Ni in a content x2, wherein 40.0 at% < x2 < 98.0 at%, preferably 50.0 at% < x2 < 95.0 at%, more preferably 55.0 at% < x2 < 90.0 at%, still more preferably 60.0 at% < x2 < 90.0 at%, relative to M2';

Co in a content y2, wherein 0.0 at% < y2 < 13.0 at%, preferably 1.0 at% < y2 < 10.0 at%, more preferably 2.0 at% < y2 < 8.0 at%, still more preferably 3.0 at% < y2 < 7.0 at%, relative to M2';

Mn in a content z2, wherein 0.0 at% < z2 < 40.0 at%, preferably 5.0 at% < z2 < 40.0 at%, more preferably 10.0 at% < z2 < 38.0 at%, still more preferably 15.0 at% < z2 < 35.0 at%, relative to M2';

D in a content a, wherein 0.0 at% < a < 5.0 at%, preferably 0.0 at% < a < 4.0 at%, more preferably 0.0 at% < a < 3.0 at%, still more preferably 0.0 at% < a < 2.0 at%, relative to M2', wherein D is at least one element selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, S, Si, Sr, Ti, Y, V, W, and Zn; and

Zr in a content b, wherein 0.0 at% < b < 2.0 at%, preferably 0.0 at% < b < 1.5 at%, more preferably 0.0 at% < b < 1.0 at%, still more preferably 0.0 at% < b < 0.5 at%, relative to M2', wherein x2, y2, z2, a, and b are measured by ICP-OES, and wherein x2+y2+z2+a + b is 100.0 at%.

In a preferred embodiment, the positive electrode active material powder comprises single particles and secondary particles, wherein each of the single particles consist of only one primary particle and each of the secondary particles consist of at least two primary particles and at most twenty primary particles as observed in a SEM image.

Positive Electrode Active Material Powder

In a third aspect, the present invention relates to a positive electrode active material powder for lithium-ion rechargeable batteries prepared by the method according to the first aspect, wherein the heated material in Step 3) is milled by wet ball milling, and wherein the positive electrode active material powder has a span being lower than or equal to 0.95, preferably 0.91, and more preferably 0.87. The inventors of the present invention have found out that the span of a positive electrode active material may be lower than or equal to 0.95, preferably 0.91, more preferably 0.87, and higher than or equal to 0.75, preferably 0.79, more preferably 0.83, when the positive electrode active material is prepared by the method according to the first aspect, and when the heated material in Step 3) of the first aspect is milled by wet ball milling.

In a preferred embodiment, D50 of the positive electrode active material powder ranges: 1.0 pm < D50 < 8.0 pm, preferably 1.3 pm < D50 < 6.0 pm, and more preferably 1.5 pm < D50 < 4.0 pm.

In a preferred embodiment, the positive electrode active material powder has D99/D50 being lower than or equal to 2.05, preferably 2.00, more preferably 1.95, and most preferably 1.90.

In a preferred embodiment, the positive electrode active material powder comprises particles comprising Li, M3', and oxygen, wherein M3' comprises:

Ni in a content x3, wherein 40.0 at% < x3 < 98.0 at%, preferably 50.0 at% < x3 < 95.0 at%, more preferably 55.0 at% < x3 < 90.0 at%, still more preferably more preferably 60.0 at% < x2 < 90.0 at%, relative to M3';

Co in a content y3, wherein 0.0 at% < y3 < 13.0 at%, preferably 1.0 at% < y3 < 10.0 at%, more preferably 2.0 at% < y3 < 8.0 at%, still more preferably 3.0 at% < y3 < 7.0 at%, relative to M3';

Mn in a content z3, wherein 0.0 at% < z3 < 40.0 at%, preferably 5.0 at% < z3 < 40.0 at%, more preferably 10.0 at% < z3 < 38.0 at%, still more preferably 15.0 at% < z3 < 35.0 at%, relative to M3';

D in a content a, wherein 0.0 at% < a < 5.0 at%, preferably 0.0 at% < a < 4.0 at%, more preferably 0.0 at% < a < 3.0 at%, still more preferably 0.0 at% < a < 2.0 at%, relative to M3', wherein D is at least one element selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, S, Si, Sr, Ti, Y, V, W, and Zn; and

Zr in a content b, wherein 0.0 at% < b < 2.0 at%, preferably 0.0 at% < b < 1.5 at%, more preferably 0.0 at% < b < 1.0 at%, still more preferably 0.0 at% < b < 0.5 at%, relative to M3', wherein x3, y3, z3, a, and b are measured by ICP-OES, and wherein x3+y3+z3+a + b is 100.0 at%.

In a preferred embodiment, the positive electrode active material powder comprises single particles and secondary particles, wherein each of the single particles consist of only one primary particle and each of the secondary particles consist of at least two primary particles and at most twenty primary particles as observed in a SEM image. Battery

In a fourth aspect, the present invention relates to a battery comprising the positive electrode active material powder according to the second and third aspects.

Use of Battery

In a fifth aspect, the present invention relates to a use of the battery according to the fourth aspect.

As appreciated by a person skilled in the art, all embodiments directed to the positive electrode active material according to the first aspect may apply mutatis mutandis to the second, third and fourth aspects.

EXPERIMENTAL ANALYSIS USED IN THE EXAMPLES

The following analysis methods are used in the Examples.

A) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) measurement

The amount of Li, Ni, Co, Mn, D, and Zr in the positive electrode active material powder is measured with the inductively coupled plasma - optical emission spectrometry (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 distribution (PSD) analysis

The particle size distribution (PSD) of the positive electrode active material is measured by laser scattering method 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. PSD may be represented by D99/D50 or span = (D90-D10)/D50, where D10, D50, D90 and D99 are defined as the particle size at 10%, 50%, 90% and 99% of the cumulative volume% distributions, respectively, obtained from the Malvern Mastersizer 3000 with Hydro MV measurements.

EXAMPLES

The present invention is further illustrated in the following examples. Example 1

A positive electrode active material powder EXI was obtained through the following steps:

1) Preparing a mixture: 1200.00 kilograms of Nio.63Mno.32Coo.os(OH)2 having D50 of 3 pm was mixed homogeneously with 317.15 kilograms of LiOH and 4.04 kilograms of ZrC>2 to prepare a mixture.

2) Heating the mixture: The mixture was heated at 965 °C for 7 hours and 40 minutes under a dry air atmosphere.

3) Milling : The heated material was milled by using jet milling. The jet milling was implemented at 0.25 MPa with 3000 rpm to obtain the positive electrode active material powder EXI.

Comparative Example 1

A positive electrode active material powder CEX1 was obtained through the following steps:

1) Preparing a mixture: 1200.00 kilograms of Nio.63Mno.32Coo.os(OH)2 having D50 of 6 pm was mixed homogeneously with 317.15 kilograms of LiOH to prepare a mixture.

3) Milling : The heated material was milled by using jet milling. The jet milling was implemented at 0.25 MPa with 3000 rpm to obtain the positive electrode active material powder CEX1.

Comparative Example 2

A positive electrode active material powder CEX2 was obtained through the following steps:

1) Preparing a mixture: 1200.00 kilograms of Nio.63Mno.32Coo.os(OH)2 having D50 of 6 pm was mixed homogeneously with 317.15 kilograms of LiOH and 4.04 kilograms of ZrO2 to obtain a mixture.

3) Milling : The heated material was milled by using jet milling. The jet milling was implemented at 0.30 MPa with 3000 rpm to obtain the positive electrode active material powder CEX2.

Table 1 below summarizes the chemical compositions analyzed by ICP-OES and the particle size distribution (PSD) of the example and the comparative examples when the example and the comparative examples were milled by using jet milling.

Table 1. Summary of ICP-OES and PSD results for the example and the comparative examples milled by jet milling

* The atomic contents were relative to total contents of Ni, Co, Mn, and Zr

The span of EXI comprising 0.25 at% Zr relative to the total contents of Ni, Co, Mn, and Zr was 1.11, while the span of CEX1 comprising no Zr was 1.43. Thus, it is confirmed that the span is lowered by adding Zr-containing compound during the step of preparing a mixture. In addition, the span of CEX2 prepared by using a precursor having a D50 of 6.0 pm was 1.39, which is higher than the span of EXI prepared by using a precursor having a D50 of 3.0 pm. Thus, it is confirmed that the span is lowered by using a transition metal composite precursor having less D50 in the step of preparing a mixture.

D99/D50 of EXI comprising 0.25 at% Zr relative to the total contents of Ni, Co, Mn, and Zr was 2.28, while D99/D50 of CEX1 comprising no Zr was 2.79. Thus, it is confirmed that D99/D50 is lowered by adding Zr-containing compound during the step of preparing a mixture. In addition, D99/D50 of CEX2 prepared by using a precursor having a D50 of 6.0 pm was 2.79, which is higher than D99/D50 of EXI prepared by using a precursor having a D50 of 3.0 pm. Thus, it is confirmed that D99/D50 is lowered by using a transition metal composite precursor having less D50 in the step of preparing a mixture.

Accordingly, it is obviously observed that the combination of using a precursor which has a lower D50 than 5.0 pm and adding a Zr source during the mixing step of the precursor and a Li source can achieve the object of the present invention, which is to provide a positive electrode active material powder having a homogeneous particle size distribution.

Example 2

A positive electrode active material powder EX2 was obtained through the following steps:

1) Preparing a mixture: 150.00 grams of Nio.63Mno.32Coo.os(OH)2 having D50 of 3 pm was mixed homogeneously with 39.64 grams of LiOH and 0.50 grams of ZrC>2 to prepare a mixture.

3) Milling: 50 grams of the heated material was bead milled in 50 grams of deionized water with ZrC>2 balls having a diameter of 10 millimeters in a 250 mL bottle at 50 rpm for 15 hours followed by drying at 120 °C and sieving process so as to obtain the positive electrode active material powder EX2. Comparative Example 3

A positive electrode active material powder CEX3 was obtained through the following steps:

1) Preparing a mixture: 150.00 grams of Nio.63Mno.32Coo.os(OH)2 having D50 of 3 pm was mixed homogeneously with 39.64 grams of LiOH to prepare a mixture.

3) Milling : 50 grams of the heated material was bead milled in 50 grams of deionized water with ZrC>2 balls having a diameter of 10 millimeters in a 250 mL bottle at 50 rpm for 15 hours followed by drying at 120 °C and sieving process so as to obtain the positive electrode active material powder CEX3.

Comparative Example 4

A positive electrode active material powder CEX4 was obtained through the following steps:

1) Preparing a mixture: 150.00 grams of Nio.63Mno.32Coo.os(OH)2 having D50 of 6 pm was mixed homogeneously with 39.64 grams of LiOH and 0.50 grams of ZrO2 to prepare a mixture.

3) Milling : 50 grams of the heated material was bead milled in 50 grams of deionized water with ZrO2 balls having a diameter of 10 millimeters in a 250 mL bottle at 50 rpm for 15 hours followed by drying at 120 °C and sieving process so as to obtain the positive electrode active material powder CEX4.

Comparative Example 5

A positive electrode active material powder CEX5 was obtained through the following steps:

1) Preparing a mixture: 150.00 grams of Nio.63Mno.32Coo.os(OH)2 having D50 of 6 pm was mixed homogeneously with 39.64 grams of LiOH.

3) Milling : 50 grams of the heated material was bead milled in 50 grams of deionized water with ZrO2 balls having a diameter of 10 millimeters in a 250 mL bottle at 50 rpm for 15 hours followed by drying at 120 °C and sieving process so as to obtain the positive electrode active material powder CEX5.

Table 2 below summarizes the chemical compositions analyzed by ICP-OES and the particle size distribution (PSD) of the example and the comparative examples when the example and the comparative examples were milled by using wet ball milling. Table 2. Summary of ICP-OES and PSD results for the example and the comparative examples milled by wet ball milling

* The atomic contents were relative to total contents of Ni, Co, Mn, and Zr

The span of EX2 comprising 0.25 at% Zr relative to the total contents of Ni, Co, Mn, and Zr was 0.86, while the span of CEX3 comprising no Zr was 1.13. Thus, it is confirmed that the span is lowered by adding Zr-containing compound during the step of preparing a mixture. In addition, the span of CEX4 prepared by using a precursor having a D50 of 6.0 pm was 0.96, which is higher than the span of EX2 prepared by using a precursor having a D50 of 3.0 pm. Thus, it is confirmed that the span is lowered by using a transition metal composite precursor having less D50 in the step of preparing a mixture.

D99/D50 of EX2 comprising 0.25 at% Zr relative to the total contents of Ni, Co, Mn, and Zr was 1.87, while D99/D50 of CEX3 comprising no Zr was 2.40. Thus, it is confirmed that D99/D50 is lowered by adding Zr-containing compound during the step of preparing a mixture. In addition, D99/D50 of CEX4 prepared by using a precursor having a D50 of 6.0 pm was 2.06, which is higher than D99/D50 of EX2 prepared by using a precursor having a D50 of 3.0 pm. Thus, it is confirmed that D99/D50 is lowered by using a transition metal composite precursor having less D50 in the step of preparing a mixture.

Accordingly, it is obviously observed that the combination of using a precursor which has D50 lower than 5.0 pm and adding a Zr source during the mixing step of the precursor and a Li source can achieve the object of the present invention, which is to provide a positive electrode active material powder having a homogeneous particle size distribution.

Claims

1. A method for preparing a positive electrode active material powder for lithium-ion rechargeable batteries, comprising:

Step 1) mixing a Li source, a transition metal precursor, and a Zr-containing source to obtain a mixture;

Step 3) milling the heated material, wherein the transition metal precursor comprises Ni, optionally Co, and optionally Mn, and wherein the transition metal precursor has a D50 value of less than 5.0 pm, D50 being defined as a particle size at 50% of cumulative volume% distribution when measured by laser scattering method, and wherein the Li source is LiOH.

2. The method according to claim 1, wherein the Zr-containing source is at least one selected from the group consisting of zirconium oxide, zirconium hydroxide, and lithium zirconium oxide.

3. The method according to claim 1 or 2, the D50 value of the transition metal precursor is less than 4.5 pm, preferably less than 4.0 pm.

4. The method according to any one of the preceding claims, wherein the mixture in Step 2) is heated for 4 to 10 hours, preferably 5 to 9 hours, more preferably 6 to 8 hours.

5. The method according to any one of the preceding claims, wherein the temperature in Step 2) is between 700 °C and 1050 °C, preferably between 750 °C and 1000 °C, more preferably 800 °C and 980 °C.

6. The method according to any one of the preceding claims, wherein the Zr-containing source in Step 1) is added in a content of 0.05-0.50 mol%, preferably 0.10-0.45 mol%, and more preferably 0.15-0.40 mol%, with respect to the Zr-containing source and the transition metal precursor.

7. The method according to any one of the preceding claims, wherein the transition metal precursor comprises particles comprising Li, Ml' and oxygen, wherein Ml' comprises:

Ni in a content xl, wherein 40.0 at% < xl < 98.0 at%, relative to Ml';

Co in a content yl, wherein 0.0 at% < yl < 15.0 at%, relative to Ml'; and Mn in a content zl, wherein 0.0 at% < zl < 45.0 at%, relative to Ml', wherein xl, yl, and zl are measured by ICP-OES, and wherein xl+yl+zl is 100.0 at%.

8. The method according to any one of the preceding claims, wherein the heated material in Step 3) is milled by a jet milling.

9. The method according to claim 8, wherein a pressure of gas introduced into an apparatus of the jet milling ranges from 0.10 MPa to 0.40 MPa, preferably from 0.15 MPa to 0.35 MPa, more preferably from 0.20 MPa to 0.30 MPa.

10. The method according to claim 9, wherein the apparatus of the jet milling comprises a classifier and a rotation speed of the classifier ranges from 1000 rpm to 5000 rpm, preferably 2000 rpm to 4000 rpm, more preferably 2500 rpm to 3500 rpm.

11. The method according to any one of claims 1 to 7, wherein the heated material in Step 3) is milled by a wet ball milling.

12. The method according to claim 11, wherein the heated material in Step 3) is mixed with a solution comprising or consisting of deionized water.

13. The method according to claim 11 or 12, wherein a grinding media used in Step 3) is at least one selected from the group consisting of ZrO?, AI2O3 and tungsten carbide beads.

14. The method according to claim 13, wherein the grinding media has a diameter between 0.5 mm and 20.0 mm, preferably 5.0 mm and 15.0 mm, more preferably between 8.0 mm to 12.0 mm.