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

Abstract

The present disclosure provides a positive electrode active material suitable for lithium-ion rechargeable batteries, comprising a mixture of a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material comprises lithium, M', and oxygen, wherein M' comprises: - Mn in a content x, wherein 50 ≤ x ≤ 90 mol%, relative to M', wherein the second positive electrode active material comprises lithium, M'', and oxygen, wherein M'' comprises: - Mn in a content x', wherein 0 < x' < 50 mol%, relative to M'', wherein a weight ratio (wt% / wt%) of the first positive active material to the second positive active material in the mixture is higher than or equal to 1 and lower than or equal to 5, and wherein, after applying a pressure of 200 MPa, a volume % (V%) of fine particles having a size less than 1 μm in the mixture is lower than 2%.

Description

[0001] POSITIVE ELECTRODE ACTIVE MATERIAL AND METHOD FOR MANUFACTURING A POSITIVE ELECTRODE ACTIVE MATERIAL

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a lithium metal-based oxide cathode active material for lithium-ion secondary batteries (LIBs) suitable for electric vehicle (EV) and hybrid electric vehicle (HEV) applications, a method of manufacturing said cathode active material, a battery comprising said cathode active material and the use of said battery.

[0004] BACKGROUND

[0005] Secondary batteries have become increasingly vital in modern energy storage systems, powering a wide array of devices ranging from portable electronics to electric vehicles. As the development of small and lightweight electronic products, electronic devices, communication devices and the like have advanced rapidly and a need for electric vehicles has widely emerged with respect to environmental issues, there is a demand for improvement of performance of secondary batteries used as power sources for these products. With the growing demand for high-capacity, long-lasting, and stable rechargeable batteries, there is a critical need for the development of advanced cathode materials that can meet the stringent requirements of various battery applications.

[0006] Lithium- and manganese-rich oxides are appealing in terms of safety and energy density. In addition, in order to improve the density of electrode plates, which are cell components, large particles and small particles should be configured in a bimodal form in which they are blended in a certain fraction.

[0007] However, positive electrode active materials composed of secondary particles in which primary particles with a size of several pm are aggregated at tens of nm has a large specific surface part of the powder and a large contact part with the electrolyte, which increases the possibility of gas generation and degrades the life characteristics.

[0008] In addition, when the cathode active material layer is formed in a bimodal shape and rolled, since the strength of the secondary particles is weak, the secondary particles, which are small particles, are broken in the form of primary particles, thereby degrading life characteristics.

[0009] Therefore, there is a need for the development of a technology capable of improving the electrochemical performance of a lithium secondary battery while forming a bimodal cathode active material layer.

[0010] It is an object of the present disclosure to provide a positive electrode active material having one or more improved properties, such as an increased life characteristics and cycle performance.

[0011] It is a further object of the present disclosure to provide a method for manufacturing the positive electrode active material.

[0012] It is a further object of the present disclosure to provide a battery comprising the positive electrode active material.

[0013] It is a further object of the present disclosure to provide a use of the battery.

[0014] SUMMARY

[0015] The present disclosure provides a positive electrode active material suitable for lithium-ion rechargeable batteries, comprising a mixture of a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material comprises lithium, M', and oxygen, wherein M' comprises:

[0016] - Mn in a content x, wherein 50 < x < 90 mol%, relative to M', wherein the second positive electrode active material comprises lithium, M", and oxygen, wherein M" comprises:

[0017] - Mn in a content x', wherein 0 < x' < 50 mol%, relative to M", wherein a weight ratio (wt% / wt%) of the first positive active material to the second positive active material in the mixture is higher than or equal to 1 and lower than or equal to 5, and wherein, after applying a pressure of 200 MPa, a volume % (V%) of fine particles having a size less than 1 pm in the mixture is lower than 2%.

[0018] A further aspect of the present disclosure provides a method for manufacturing of a positive electrode active material, wherein said method comprises steps of: a. For obtaining a first positive electrode active material: i. Providing a starting material comprising a Li source and a transition metal composite precursor; ii. Mixing the starting material to obtain a mixture; iii. Heating the mixture at a temperature between 800 °C and 1100 °C to obtain a heated material; iv. Mixing the heated material with water followed by drying at a temperature between 80 °C and 120 °C so as to obtain a first positive electrode active material, b. For obtaining a second positive electrode active material: i. Providing a second starting material comprising a Li source and a second transition metal composite precursor; ii. Mixing the starting material to obtain a second mixture; iii. Heating the second mixture at a temperature between 650 °C and 1000 °C to obtain a second heated material; iv. Milling the second heated material to obtain a milled material; v. Heating the milled material at a temperature between 250 °C and 500 °C so as to obtain a second positive electrode active material, c. Mixing the first and the second positive electrode active material, so as to obtain the positive electrode active material.

[0019] A further aspect of the present disclosure provides a battery comprising the positive electrode active material.

[0020] A further aspect of the present disclosure provides a use of the battery.

[0021] DETAILED DESCRIPTION

[0022] In the following detailed description, preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. On the contrary, the invention includes numerous alternatives, modifications, and equivalents as will become apparent from consideration of the following detailed description and accompanying drawings. Furthermore, where feasible, each element of the described alternatives, modifications, and equivalents may be combined with any other element of the alternatives, modifications, or equivalents.

[0023] The term "comprising", as used herein and in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a composition comprising components A and B" should not be limited to compositions consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the composition are A and B. Accordingly, the terms "comprising" and "including" encompass the more restrictive terms "consisting essentially of" and "consisting of".

[0024] A positive electrode active material is defined as a material which is electrochemically active in a positive electrode. By active material, it must be understood a material capable of capturing and releasing Li ions when subjected to a voltage change over a predetermined period of time.

[0025] In the framework of the present disclosure, mol% signifies molar percentage. The mol% or "mol percent" of a given element expression of a concentration means how many percent of all atoms in the concerned compound are atoms of said element. The designation mol% is equivalent to at% or atomic percent.

[0026] Positive electrode active material

[0027] The present disclosure provides a positive electrode active material suitable for lithium-ion rechargeable batteries, comprising a mixture of a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material comprises lithium, M', and oxygen, wherein M' comprises:

[0028] - Mn in a content x, wherein 50 < x < 90 mol%, relative to M', wherein the second positive electrode active material comprises lithium, M", and oxygen, wherein M" comprises:

[0029] - Mn in a content x', wherein 0 < x' < 50 mol%, relative to M",

[0030] Wherein a weight ratio (wt% / wt%) of the first positive active material to the second positive active material in the mixture is higher than or equal to 1 and lower than or equal to 5.

[0031] A preferred embodiment is the positive electrode active material according to the present disclosure, wherein the first positive electrode active material comprises lithium, M', and oxygen, wherein M' comprises:

[0032] - Mn in a content x, wherein 50 < x < 90 mol%, relative to M',

[0033] - Ni in a content y, wherein 10 < y < 50 mol%, relative to M',

[0034] - D in a content z, wherein 0 < z < 5 mol%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Co, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn and Zr.

[0035] Preferably, the Mn content x is 50 mol% or more than 50 mol% relative to M', preferably more than 55 mol% relative to M', more preferably more than 60 mol% relative to M'. Preferably, the Mn content x is less than 90 mol% relative to M', preferably less than 80 mol% relative to M', more preferably less than 70 mol% relative to M'. Preferably, the Mn content x is in the range of 50 < x < 90 mol% relative to M', preferably, in the range of 55 < x < 75 mol% relative to M', more preferably, in the range of 60 < x < 70 mol% relative to M'.

[0036] Preferably, the Ni content y is more than 10 mol% relative to M', preferably more than 20 mol% relative to M', more preferably more than 30 mol% relative to M'. Preferably, the Ni content y is less than 50 mol% relative to M', preferably less than 45 mol% relative to M', more preferably less than 40 mol% relative to M'. Preferably, the Ni content y is in the range of 10 < y < 50 mol% relative to M', preferably, in the range of 20 < y < 45 mol% relative to M', more preferably, in the range of 30 < y < 40 mol% relative to M'.

[0037] Preferably, the dopant and / or coating material (D) content z is 0 mol% or more than 0 mol% relative to M'. Preferably, z is less than or equal to 5 mol% relative to M', preferably less than or equal to 4 mol% relative to M', more preferably less than or equal to 3 mol% relative to M'. Preferably, z is in the range of 0 < z < 5 mol% relative to M', preferably, in the range of 0 < z < 4 mol% relative to M', more preferably, in the range of 0 < z < 3 mol% relative to M'. Preferably, D comprises at least one element selected from Al, B, Ba, Ca, Co, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn and Zr. Preferably, D comprises at least one element selected from Al, Co, Mg, Nb, S, Ti, V, W, Zn and Zr; and more preferably, selected from Al, Co, Mg, Nb, S, Ti, W and Zr.

[0038] A preferred embodiment is the positive electrode active material according to the present disclosure, wherein a molar ratio of lithium to M' (mol / mol) of the first positive active material is higher than or equal to 0.9, preferably higher than or equal to 1, preferably higher than or equal to 1.1, and more preferably higher than or equal to 1.2. Preferably, the molar ratio of lithium to M' (mol / mol) of the first positive active material is less than or equal to 1.8, preferably less than or equal to 1.7, preferably less than or equal to 1.6, and more preferably less than or equal to 1.4. Preferably, the molar ratio of lithium to M' (mol / mol) of the first positive active material is between 0.9 and 1.8, preferably between 1 and 1.7, preferably between 1.1 and 1.6, more preferably between 1.2 and 1.4.

[0039] Preferably, a particle size distribution value (D50) of the first positive active material is higher than or equal to 8 pm, preferably higher than or equal to 9 pm, preferably higher than or equal to 10 pm, and more preferably higher than or equal to 11 pm. Preferably, the particle size distribution value (D50) of the first positive active material is less than or equal to 20 pm, preferably less than or equal to 18 pm, preferably less than or equal to 16 pm, and more preferably less than or equal to 15 pm. Preferably, the particle size distribution value (D50) of the first positive active material is between 8 and 20, preferably between 9 and 18, preferably between 10 and 16, and more preferably between 11 and 15.

[0040] A preferred embodiment is the positive electrode active material according to the present disclosure, wherein the second positive electrode active material comprises lithium, M", and oxygen, wherein M" comprises:

[0041] - Mn in a content x', wherein 0 < x' < 50 mol%, relative to M",

[0042] - Ni in a content y', wherein 50 < y' < 90 mol%, relative to M", - D' in a content z', wherein 0 < z' < 5 mol%, relative to M", wherein D' comprises at least one element selected from Al, B, Ba, Ca, Co, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn and Zr.

[0043] Preferably, the Mn content x' is more than 0 mol% relative to M", preferably more than or equal to 5 mol% relative to M", more preferably more than or equal to 10 mol% relative to M". Preferably, the Mn content x' is less than 50 mol% relative to M", preferably less than or equal to 40 mol% relative to M", preferably less than or equal to 35 mol% relative to M", more preferably less than or equal to 30 mol% relative to M". Preferably, the Mn content x' is in the range of 0 < x' < 50 mol% relative to M", preferably, in the range of 5 < x' < 40 mol%, relative to M", preferably 10 < x' < 35 mol%, relative to M", and more preferably 10 < x' < 30 mol%, relative to M".

[0044] Preferably, the Ni content y' is more than or equal to 50 mol% relative to M", preferably more than or equal to 55 mol% relative to M", more preferably more than or equal to 60 mol% relative to M". Preferably, the Ni content y' is less than or equal to 90 mol% relative to M", preferably less than or equal to 85 mol% relative to M", more preferably less than or equal to 80 mol% relative to M". Preferably, the Ni content y' is in the range of 50 < y' < 90 mol% relative to M", preferably, in the range of 55 < y' < 85 mol% relative to M", more preferably, in the range of 60 < y' < 80 mol% relative to M".

[0045] Preferably, the dopant and / or coating material (D') content z' is 0 mol% or more than 0 mol% relative to M". Preferably, z' is less than or equal to 5 mol% relative to M", preferably less than or equal to 4 mol% relative to M", more preferably less than or equal to 3 mol% relative to M". Preferably, z' is in the range of 0 < z' < 5 mol% relative to M", preferably, in the range of 0 < z' < 4 mol% relative to M", more preferably, in the range of 0 < z' < 3 mol% relative to M". Preferably, D' comprises at least one element selected from Al, B, Ba, Ca, Co, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn and Zr. Preferably, D' comprises at least one element selected from Al, Co, Mg, Nb, S, Ti, V, W, Zn and Zr; and more preferably, selected from Al, Co, Mg, Nb, S, Ti, W and Zr.

[0046] A preferred embodiment is the positive electrode active material according to the present disclosure, wherein a molar ratio of lithium to M" (mol / mol) of the second positive active material is higher than or equal to 0.9, preferably higher than or equal to 0.95, and more preferably higher than or equal to 1. Preferably, the molar ratio of lithium to M" (mol / mol) of the first positive active material is less than or equal to 1.5, preferably less than or equal to 1.4, preferably less than or equal to 1.3, and more preferably less than or equal to 1.2. Preferably, the molar ratio of lithium to M" (mol / mol) of the second positive active material is between 0.9 and 1.5, preferably between 0.95 and 1.4, preferably between 1 and 1.3, more preferably between 1 and 1.2.

[0047] Preferably, a particle size distribution value (D50) of the second positive active material is higher than or equal to 1 pm, and more preferably higher than or equal to 2 pm. Preferably, the particle size distribution value (D50) of the second positive active material is less than or equal to 8 pm, preferably less than or equal to 7 pm, preferably less than or equal to 6 pm, preferably less than or equal to 5 pm, and more preferably less than or equal to 4 pm. Preferably, the particle size distribution value (D50) of the second positive active material is between 1 and 8, preferably between 1 and 7, preferably between 2 and 6, preferably between 2 and 5, and more preferably between 2 and 4.

[0048] In a preferred embodiment the present disclosure provides the positive electrode active material comprising a mixture of the first positive electrode active material and the second positive electrode active material. Preferably in the mixture, the amount of the first positive electrode active material is higher than or equal to 10 wt% relative to the mixture, preferably higher than or equal to 15 wt% relative to the mixture, preferably higher than or equal to 20 wt% relative to the mixture, preferably higher than or equal to 25 wt% relative to the mixture, preferably higher than or equal to 30 wt% relative to the mixture, preferably higher than or equal to 35 wt% relative to the mixture, preferably higher than or equal to 40 wt% relative to the mixture, preferably higher than or equal to 45 wt% relative to the mixture, preferably higher than or equal to 50 wt% relative to the mixture, preferably higher than or equal to 55 wt% relative to the mixture. Preferably in the mixture, the amount of the first positive electrode active material is less than or equal to 95 wt% relative to the mixture, preferably less than or equal to 90 wt% relative to the mixture, preferably less than or equal to 85 wt% relative to the mixture, preferably less than or equal to 80 wt% relative to the mixture, preferably less than or equal to 75 wt% relative to the mixture. In a preferred embodiment, the amount of the first positive electrode active material is between 40 and 90, preferably between 45 and 85, preferably between 50 and 80, and more preferably between 55 and 75.

[0049] Preferably in the mixture, the amount of the second positive electrode active material is higher than or equal to 5 wt% relative to the mixture, preferably higher than or equal to 10 wt% relative to the mixture, preferably higher than or equal to 15 wt% relative to the mixture, preferably higher than or equal to 20 wt% relative to the mixture, preferably higher than or equal to 25 wt% relative to the mixture. Preferably in the mixture, the amount of the second positive electrode active material is less than or equal to 95 wt% relative to the mixture, preferably less than or equal to 90 wt% relative to the mixture, preferably less than or equal to 85 wt% relative to the mixture, preferably less than or equal to 80 wt% relative to the mixture, preferably less than or equal to 75 wt% relative to the mixture, preferably less than or equal to 70 wt% relative to the mixture, preferably less than or equal to 65 wt% relative to the mixture, preferably less than or equal to 60 wt% relative to the mixture, preferably less than or equal to 55 wt% relative to the mixture, preferably less than or equal to 50 wt% relative to the mixture, preferably less than or equal to 45 wt% relative to the mixture. In a preferred embodiment, the amount of the second positive electrode active material is between 10 and 60, preferably between 15 and 55, preferably between 20 and 50, and more preferably between 25 and 45.

[0050] In a preferred embodiment the weight ratio (wt% / wt%) of the first positive active material to the second positive active material in the mixture is higher than or equal to 0.6 and lower than to equal to 9, preferably higher than or equal to 0.8 and lower than to equal to 6, preferably higher than or equal to 1 and lower than to equal to 4.5, preferably higher than or equal to 1.1 and lower than to equal to 4, preferably higher than or equal to 1.2 and lower than or equal to 3.5, and more preferably higher than or equal to 1.2 and lower than or equal to 3.

[0051] The positive electrode active material comprising the mixture of the first positive electrode active material and the second positive electrode active material of the present disclosure can minimize the generation of fine particles and suppress the generation of additional fine particles even under high pressure condition, and thus, lower the possibility of gas generation and thereby the present disclosure provides the positive electrode active material with excellent cycle characteristics, electrochemical characteristics and life characteristics.

[0052] In a preferred embodiment the present disclosure provides the positive electrode active material comprising a mixture of the first positive electrode active material and the second positive electrode active material, wherein a volume % (V%) of fine particles less than 1 pm to the mixture of a first positive electrode active material and a second positive electrode active material is lower than 3%, preferably lower than 2%, preferably lower than 1%, preferably lower than 0.5%, preferably lower than 0.3%, and more preferably lower than 0.2%. A volume % (V%) of fine particles less than 1 pm to the mixture of a first positive electrode active material and a second positive electrode active material is defined as the cumulative volume percentage of particles with a size below 1 pm in the particle size distribution.

[0053] Preferably after 200MPa pressure applied, the present disclosure provides the positive electrode active material comprising a mixture of the first positive electrode active material and the second positive electrode active material, wherein a volume % (V%) of fine particles less than 1 pm is lower than 3%, preferably lower than 2%, preferably lower than 1%, preferably lower than 0.8%, preferably lower than 0.6%, preferably lower than 0.5%, and more preferably lower than 0.3%. To press with 200 MPa pressure, for example, about 3.0 grams of powder was filled into a pellet die having an inner diameter of 1.30 cm. A uniaxial load pressure of 200 MPa was applied to the powder in pellet die for 3 minutes and 30 seconds.

[0054] As appreciated by the skilled person the amount of Li, Ni, Mn and others measured with Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). For example, but not limiting to the invention, an Agilent ICP 720-ES is used in the ICP-OES analysis. In the framework of the present invention, "atomic content" of a given element expression of a concentration means how many percent of all atoms in the concerned compound are atoms of said element. The designation mol% is equivalent to "molar percent" or "at%".

[0055] Method for Preparing Positive Electrode Active Material

[0056] Hereinafter, a method for preparing a positive electrode active material according to an embodiment of the present disclosure will be described in detail. A positive electrode active material is prepared according to the following steps: a. For obtaining a first positive electrode active material: i. Providing a starting material comprising a Li source and a transition metal composite precursor; ii. Mixing the starting material to obtain a mixture; iii. Heating the mixture at a temperature between 800 °C and 1100 °C to obtain a heated material; iv. Mixing the heated material with water followed by drying at a temperature between 80 °C and 120 °C so as to obtain a first positive electrode active material, b. For obtaining a second positive electrode active material: i. Providing a second starting material comprising a Li source and a second transition metal composite precursor; ii. Mixing the starting material to obtain a second mixture; iii. Heating the second mixture at a temperature between 650 °C and 1000 °C to obtain a second heated material; iv. Milling the second heated material to obtain a milled material; v. Heating the milled material at a temperature between 250 °C and 500 °C so as to obtain a second positive electrode active material, c. Mixing the first and the second positive electrode active material, so as to obtain the positive electrode active material.

[0057] Battery

[0058] The present disclosure provides a battery comprising the positive electrode active material.

[0059] In a preferred embodiment the battery is a lithium-ion battery, preferably a lithium-ion rechargeable battery. The battery according to an embodiment of the present disclosure includes the positive electrode active material, a binder, a conductor, and a solvent. The positive electrode active material is as described above, and a binder, a conductor, and a solvent are not particularly limited as long as these can be used on a cathode current collector for a secondary battery.

[0060] Use

[0061] The present disclosure provides a use of the positive electrode active material. A preferred embodiment is the use of the positive electrode active material in a battery, to increase the efficiency of the battery. Furthermore, the present disclosure provides a use of the battery in either one of a portable computer, a tablet, a mobile phone, an energy storage system (ESS), an electric vehicle (EV) or in a hybrid electric vehicle (HEV), preferably in an electric vehicle or in a hybrid electric vehicle that includes the positive electrode active material according to the disclosure.

[0062] EXPERIMENTAL TESTS USED IN THE EXAMPLES

[0063] The following analysis methods are used in the Examples and the Comparative Examples:

[0064] A) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) measurement

[0065] 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.

[0066] B) Particle size analysis

[0067] 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 and <lpm (%) is defined as the cumulative volume% distributions of the particles having size below 1 pm. EXAMPLES

[0068] The present invention is further illustrated in the following examples.

[0069] Positive electrode active material 1 (CAM1)

[0070] A positive electrode active material CAM1 was obtained through following steps: a. Precursor roasting: a precursor having transition metal composition as Nio.3s4Mno.6i6 in carbonate form was roasted in an O2 atmosphere at 400 °C for 10 hours followed by cooling to room temperature naturally to prepare a roasted precursor. b. First mixing: the roasted precursor was mixed homogeneously with Li2COs and U2SO4, wherein the molar ratio of Li to total amount of Ni, Mn, and Co is 1.31, to prepare a first mixture. c. First heating : the first mixture was heated at 925 °C for 10 hours followed by cooling, grinding, and sieving to prepare a first heated material. d. Washing: the first heated material was washed in deionized water followed by filtering and drying so as to obtain CAM1.

[0071] Positive electrode active material 2 (CAM2)

[0072] A positive electrode active material CAM2 was obtained through following steps: a. First mixing: a precursor powder having transition metal composition as Nio.75Mno.25 in hydroxide or oxyhydroxide form was mixed homogeneously with LiOH and ZrC>2 to prepare a first mixture, wherein 0.1 wt% Zr relative to amount of the precursor powder was added. b. First heating: the first mixture was heated at 845 °C for 15 hours under oxygen atmosphere followed by cooling, grinding, and sieving to prepare a first heated material. c. Bead-milling: the first heated material was milled with beads in an aqueous solution containing Al2(SO4)s followed by filtering and drying to prepare a milled material, wherein 0.02 wt% Al relative to amount of the first heated material was contained in the aqueous solution and the target D50 of the milled material was 2.8-3.0 pm. d. Second mixing: the milled material was mixed homogeneously with H3BO3 and WO3 to prepare a second mixture, wherein 0.025 wt% B and 0.3 wt% W relative to amount of the milled material were added. e. Second heating: the second mixture was heated at 375 °C for 13 hours followed by cooling, grinding, and sieving so as to obtain CAM2.

[0073] Comparative Examples 1-3 (CEX1, CEX2, CEX3) and Examples 1-3 (EXI, EX2, EX3) The positive electrode active material CEX1, CEX2, CEX3, EXI, EX2, and EX3 were prepared by blending CAM1 and CAM2 according to the weight ratios in Table 1 below. Table 1. Blending ratio to prepare CEX1, CEX2, CEX3, EXI, EX2, and EX3

[0074] The elemental composition of CAM1 and CAM2 were analyzed by ICP-OES and D50 of CAM1 and CAM2 were analyzed by PSD. The results of ICP-OES and PSD are summarized in Table 2.

[0075] Table 2. Summary of ICP-OES and PSD results of CAM1 and CAM2

[0076] CAM1 and relative to total contents of Ni, Mn, and D' for CAM2. Table 3 summarizes volume% of fine particles having lower size than 1 pm before and after pressing with 200 MPa pressure of Comparative Examples and Examples. To press with 200 MPa pressure, about 3.0 grams of powder was filled into a pellet die having an inner diameter of 1.30 cm. A uniaxial load pressure of 200 MPa was applied to the powder in pellet die for 3 minutes and 30 seconds.

[0077] Table 3. PSD results for CEX1, CEX2, CEX3, EXI, EX2, and EX3 before and after pressing

[0078] According to Table 3, the fine particle having lower size than 1 pm increased as 2.43 vol% when CEX1 was pressed with 200 MPa pressure. CEX1 consisted of Mn-based transition metal oxide CAM1 which could implemented in a high voltage cycling, however, the generation of fine particles after pressing should be solved. CEX3 comprises 85 wt% CAM1 and 15 wt% CAM2, wherein fine particles were generated as 2.04 vol% alike CEX1. The generation of fine particles has been significantly reduced In EXI, EX2, and EX3 which comprise 75 wt%, 65 wt%, and 55 wt% CAM1 where vol% of the increased fine particle were improved as 0.18 vol%, 0.21 vol%, and 0.16 vol% respectively.

[0079] These results show that the present disclosure comprising mixture of a Mn-based transition metal oxide and a positive electrode active material comprising lower Mn than 50 at% relative to total amount of Ni, Mn, and D' exhibits the lower volume% of fine particle generation after pressing.

Claims

CLAIMS1. A positive electrode active material suitable for lithium-ion rechargeable batteries, comprising a mixture of a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material comprises lithium, M', and oxygen, wherein M' comprises:- Mn in a content x, wherein 50 < x < 90 mol%, relative to M', wherein the second positive electrode active material comprises lithium, M", and oxygen, wherein M" comprises:- Mn in a content x', wherein 0 < x' < 50 mol%, relative to M", wherein a weight ratio (wt% / wt%) of the first positive active material to the second positive active material in the mixture is higher than or equal to 1 and lower than or equal to 5, and wherein, after applying a pressure of 200 MPa, a volume % (V%) of fine particles having a size less than 1 pm in the mixture is lower than 2%.

2. The positive electrode active material according to claim 1, wherein a molar ratio of lithium to M' (mol / mol) of the first positive active material is between 0.9 and 1.8, preferably between 1 and 1.7, preferably between 1.1 and 1.6, more preferably between 1.2 and 1.4.

3. The positive electrode active material according to any of the previous claims, wherein the first positive active material is polycrystalline consisting of a plurality of primary particles, wherein M' comprises:Ni in a content y, wherein 10 < y < 50 mol%, relative to M', Wherein the second positive active material comprises single crystal particles, wherein M" comprises:Ni in a content y', wherein 50 < y' < 90 mol%, relative to M".

4. The positive electrode active material according to any of the previous claims, wherein a particle size distribution value (D50) of the first positive active material is higher than or equal to 8 pm and lower than or equal to 20 pm, preferably higher than or equal to 9 pm and lower than or equal to 18 pm, preferably higher than or equal to 10 pm and lower than or equal to 16 pm, and more preferably higher than or equal to 11 pm and lower than or equal to 15 pm.

5. The positive electrode active material according to any of the previous claims, wherein a particle size distribution value (D50) of the second positive active material is higher than or equal to 1 pm and lower than or equal to 8 pm, preferably higher than or equal to 1 pm and lower than or equal to 7 pm, preferably higher than or equal to 2 pm and lower than or equal to 6 pm, preferably higher than or equal to 2 pm and lower than or equal to 5 pm, and more preferably higher than or equal to 2 pm and lower than or equal to 4 pm.

6. The positive electrode active material according to any of the previous claims, wherein, after applying a pressure of 200 MPa, the volume % (V%) of fine particles having a size less than 1 pm in the mixture is lower than 1%, preferably 0.6%, and more preferably 0.3%.

7. The positive electrode active material according to any of the previous claims, wherein the weight ratio (wt% / wt%) of the first positive active material to the second positive active material in the mixture is preferably higher than or equal to 1.1 and lower than or equal to 4, preferably higher than or equal to 1.2 and lower than or equal to 3.5, and more preferably higher than or equal to 1.2 and lower than or equal to 3.

8. The positive electrode active material according to any of the previous claims, wherein the first positive active material comprises D in a content z, wherein 0 < z < 5 mol%, relative to M', wherein D comprises at least one element selected from Al, B, Ba, Ca, Co, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn and Zr.

9. The positive electrode active material according to any of the previous claims, wherein the second positive active material comprises D' in a content z', wherein 0 < z' < 5 mol%, relative to M", wherein D' comprises at least one element selected from Al, B, Ba, Ca, Co, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn and Zr.

10. The positive electrode active material according to any of the previous claims, wherein 50 < x < 80 mol%, relative to M', preferably 55 < x < 75 mol%, relative to M', and more preferably 60 < x < 70 mol%, relative to M'.

11. The positive electrode active material according to any of the previous claims, wherein 5< x' < 40 mol%, relative to M", preferably 10 < x' < 35 mol%, relative to M", and more preferably 10 < x' < 30 mol%, relative to M",12. A method of preparing a positive electrode active material, preferably a positive electrode active material according to any one of preceding claims, comprising:A. For obtaining a first positive electrode active material: i. Providing a starting material comprising a Li source and a transition metal composite precursor; ii. Mixing the starting material to obtain a mixture; iii. Heating the mixture at a temperature between 800 °C and 1100 °C to obtain a heated material; iv. Mixing the heated material with water followed by drying at a temperature between 80 °C and 120 °C so as to obtain a first positive electrode active material,B. For obtaining a second positive electrode active material: i. Providing a second starting material comprising a Li source and a second transition metal composite precursor; ii. Mixing the starting material to obtain a second mixture; iii. Heating the second mixture at a temperature between 650 °C and 1000 °C to obtain a second heated material; iv. Milling the second heated material to obtain a milled material; v. Heating the milled material at a temperature between 250 °C and 500 °C so as to obtain a second positive electrode active material,C. Mixing the first and the second positive electrode active material, so as to obtain the positive electrode active material.

13. The method of preparing a positive electrode active material according to claim 12, the milling step for the second positive electrode active material is one method selected from wet bead-mill and jet-mill.

14. A battery comprising the positive electrode active material according to any one of claims 1 to 11.

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

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