Positive Electrode Active Material and Method for Producing Positive Electrode Active Material

Abstract

A positive electrode active material, wherein the metal has a composition M, M consists of Ni with a content of x, Mn with a content of y, Co with a content of z, and A with a content of a, A is at least one chemical element other than Li, Ni, Mn, Co, and O, x, y, z, and a are expressed as molar contents, x + y + z + a = 100%, wherein x ≥ 70.0%, 0 ≤ y ≤ 30.0%, 0 ≤ z ≤ 30.0%, 0 ≤ a ≤ 5.0%, the X-ray diffractogram of the positive electrode active material from a Cu K-α X-ray source has a (003) peak located at 2θ = 17.0° to 20.0° and a (104) peak located at 2θ = 43.0° to 46.0°, and the ratio ((maximum intensity of the (003) peak) / ((maximum intensity of the (104) peak)) is at least 1.880. A method for manufacturing such a positive electrode active material is further disclosed.

Description

Technical Field

[0001] The present invention relates to a positive electrode active material containing lithium, a metal other than lithium, and oxygen, and in particular to a positive electrode active material in which the metal has a high Ni content, typically 70 mol% or more based on the total transition metal content.

Background Art

[0002] Such a positive electrode active material is known, for example, from Korean Patent Application Publication No. 20210018139(A).

[0003] The positive electrode active material preferably has a regular crystal structure. However, in materials according to the prior art, Ni 2+ is present on the Li + sites in the crystal lattice, which reduces the performance (increase in the soluble base content on the surface and formation of an insulating surface layer due to Li 2+ substitution from Ni + ).

[0004] The peak intensity ratio of the (003) / (104) peaks in the XRD diffractogram is well known to be useful as a reliable indicator of the degree of cation mixing, in other words, the occupancy of Ni + on the Li 2+ sites in the layered oxide.

[0005] This is particularly relevant for monolithic positive electrode active materials produced at a higher temperature than polycrystalline positive electrode active materials.

[0006] In the production of such a positive electrode active material, a certain amount of unreacted Li compound may remain (usually as LiOH). This is undesirable for the performance of the positive electrode active material in the battery, and it also means that more lithium source material needs to be used than is strictly necessary, leading to waste of the lithium source material.

[0007] Several attempts have been described to improve battery performance through the temperature profile during heating of the positive electrode active material. However, most of these efforts have focused on a stepwise increase in the heating temperature.

[0008] In contrast, there are only very few publications directed towards managing the cooling profile.

[0009] For example, International Publication No. WO 2020 / 216888 (A1) of Umicore describes a three-step cooling: · Cooling to below 700 °C, · Cooling to below 550 °C at a cooling rate of 2 - 10 °C / min, · Cooling to ambient temperature.

[0010] Chinese Patent Application Publication No. CN 110233250 (A) describes a method of performing a second heating step at a low temperature of 600 °C to 800 °C after stepwise increasing the heating temperature.

[0011] U.S. Patent Application Publication No. US 2009 / 299922 (A1) of Toda Kogyo describes the cooling rate of the positive electrode active material at a cooling rate of less than 20 °C / min, more specifically, between 3 °C / min and 20 °C / min, or between 3 °C / min and 14 °C / min, or between 3 °C / min and 10 °C / min, or between 3 °C / min and 9 °C / min, or less than 8 °C / min.

[0012] U.S. Patent Application Publication No. US 2013 / 011726 (A1) of Mitsubishi describes generally reducing the temperature inside the furnace at a cooling rate of 0.1 - 15 °C / min. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, there is still a need to provide an improved industrial-scale process that enables a positive electrode active material with reduced impurity levels and improved lithium distribution in order to achieve improved battery performance. MEANS FOR SOLVING THE PROBLEMS

[0014] The inventors have now surprisingly found that the method according to the present invention reduces the level of lithium impurities and improves the cathode active material.

[0015] Accordingly, a first aspect of the present invention is a cathode active material containing lithium, a metal other than lithium, and oxygen, wherein the metal has a composition M, M consists of Ni with a content of x, Mn with a content of y, Co with a content of z, and A with a content of a, A is at least one chemical element other than Li, Ni, Mn, Co, and O, x, y, z, and a are represented as molar contents, and x + y + z + a = 100 mol%, · wherein x ≥ 70.0 mol%, · 0 ≤ y ≤ 30.0 mol%, · 0 ≤ z ≤ 30.0 mol%, · 0 ≤ a ≤ 5.0 mol%, The X-ray diffractogram of the cathode active material obtained from a Cu K-α X-ray source has a (003) peak located at 2θ = 17.0° to 20.0° and a (104) peak located at 2θ = 43.0° to 46.0°, and the ratio ((maximum intensity of the (003) peak) / (maximum intensity of the (104) peak)) is at least 1.880 or more, which is the cathode active material.

[0016] The advantage is that such a cathode active material has better performance than known cathode active materials.

[0017] Preferably, x, y, z, and a are measured by ICP-OES (inductively coupled plasma).

[0018] In one embodiment, the element A is selected from the group consisting of Ag, Al, As, Au, B, Ba, Bi, Ca, Ce, Cd, Cr, Cs, Eu, Fe, Ga, Ge, Hg, Sb, Se, In, Ir, K, La, Mg, Mo, Na, Nb, Nd, Os, P, Pb, Pd, Pr, Pt, Rb, Re, Rh, Ru, S, Sc, Se, Si, Sm, Sr, Ta, Te, Ti, Y, V, W, Zn, and Zr, or a combination thereof.

[0019] Preferably, element A is selected from the group consisting of Al, As, B, Ba, Ca, Ce, Cd, Cr, Cs, Fe, Ga, Ge, Se, In, Ir, K, Mg, Mo, Na, Nb, Nd, P, Pd, Pt, S, Sc, Se, Si, Sr, Ta, Te, Ti, Y, V, W, Zn, and Zr, or combinations thereof.

[0020] Even more preferably, element A is selected from the group consisting of Al, Ba, Ca, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, W, and Zn, or combinations thereof.

[0021] Preferably, 0 < y ≤ 30.0 mol% and 0 < z ≤ 30.0 mol%.

[0022] XRD diffractogram In a preferred embodiment, the ratio (maximum intensity of (003) peak) / (maximum intensity of (104) peak) is at least 1.900, more preferably at least 1.920.

[0023] Thereby, the beneficial effects of the present invention exist to a greater extent.

[0024] In a preferred embodiment, the ratio (maximum intensity of (003) peak) / (maximum intensity of (104) peak) is at most 3.000.

[0025] In a certain preferred embodiment, the molar ratio: Li / (metal elements other than Li) in the first positive electrode active material is at least 0.90 and at most 1.10.

[0026] High-nickel positive electrode active material The present invention particularly relates to a high-nickel positive electrode active material.

[0027] Therefore, in a preferred embodiment, x, y, z are: ·x > 80.0 mol%, more preferably x > 85.0 mol%, even more preferably x > 88.0 mol%, and / or ·x < 98.5 mol%, preferably x < 97.0 mol%, and / or ·y ≤ 20.0 mol%, preferably y ≤ 10.0 mol%, and / or ·z ≤ 20.0 mol%, preferably z ≤ 10.0 mol%, and / or ·(y + z) > 1.0 mol%, preferably (y + z) > 2.5 mol%, and / or ·y > 0.5 mol%, z > 0.5 mol%.

[0028] LiOH content In a preferred embodiment, the cathode active material contains LiOH at a content of at most 0.20 wt%, preferably at most 0.15 wt%, based on the total weight of the cathode active material, and the content of LiOH is measured by acid-base titration as described herein.

[0029] LiOH impurities in the cathode active material significantly reduce the performance of the final battery, and therefore, it is necessary to reduce them as much as possible.

[0030] In a preferred embodiment, the molar ratio: Li / (metal elements other than Li) in the first cathode active material is at least 0.90 and at most 1.10.

[0031] Monolithic Preferably, the cathode active material is a powder, in other words, a plurality of particles. More preferably, the cathode active material is a powder, and most of the particles therein are monolithic particles. Such a powder is also known as a monolithic particle-based powder.

[0032] Particles are considered monolithic when they consist of only one primary particle or at most four, preferably at most three, constituent primary particles as observed in SEM images. An example of a powder having monolithic particles is shown in Figure 3.

[0033] In the determination of monolithic particles, primary particles having a maximum linear dimension observed by SEM that is less than 20% of the median particle diameter D50 of the particles determined by laser diffraction are ignored. This avoids inadvertently considering as non-monolithic particles that are essentially monolithic but may have some very small other primary particles deposited thereon.

[0034] Preferably, in the SEM image of the positive electrode active material powder, at least 50%, more preferably at least 80% of the particles within a field of view of at least 45 μm × at least 60 μm (i.e., at least 2700 μm 2 ) and preferably at least 100 μm × 100 μm (i.e., at least 10,000 μm 2 ) are monolithic.

[0035] Since primary particles can also be called granules, by observing grain boundaries, primary particles can be distinguished from each other.

[0036] The present invention also provides a first method for producing a positive electrode active material containing lithium, a metal other than lithium, and oxygen, wherein the metal has a composition M, M consists of Ni with a content of x, Mn with a content of y, Co with a content of z, and A with a content of a, A is at least one chemical element other than Li, Ni, Mn, Co, and O, x, y, z, and a are expressed as molar contents, x + y + z + a = 100 mol%, wherein x ≥ 70.0 mol%, 0 ≤ y ≤ 30.0 mol%, 0 ≤ z ≤ 30.0 mol%, 0 ≤ a ≤ 5.0 mol%, the following continuous steps: a. Heating the precursor material at a heating temperature T1 between 750 °C and 1000 °C, preferably between 800 °C and 950 °C, more preferably between 850 °C and 925 °C for a period t1 between 2 and 20 hours, preferably between 3 and 15 hours, and even more preferably between 4 and 10 hours to obtain a heated product; b. Cool the heated product to a second temperature T2 between 600 °C and 800 °C, preferably between 625 °C and 775 °C, more preferably between 650 °C and 750 °C, even more preferably between 675 °C and 725 °C, to obtain a second heated product, and obtain a first cooled product with an average cooling rate between 10 °C / hour and 50 °C / hour, preferably between 20 °C / hour and 40 °C / hour, more preferably between 25 °C / hour and 35 °C / hour. c. A step of further cooling the first cooled product, preferably to ambient temperature, to obtain a second cooled product, wherein the further cooling is preferably natural cooling. d. A step of milling and pulverizing the second cooled product to obtain a pulverized product. e. A step of heating the pulverized product at a temperature T3 between 200 °C and 900 °C to obtain a positive electrode active material, which relates to a first method.

[0037] In a preferred variant of the first method, during step b, the heated product is subjected to a temperature that is decreased at an average rate of at most 45 °C / hour, preferably at most 35 °C / hour, over the duration of the second heat treatment step.

[0038] In a preferred variant of the first method, throughout the duration of step b, the heated product is subjected to a temperature that either decreases over time or remains constant over time. Obviously, such a method can be carried out in an industrial furnace where rapid temperature changes are not possible, so these terms must be understood in the context of what is actually possible in an industrial-scale furnace.

[0039] In one embodiment, the temperature of the method of the present invention is the set temperature of the furnace.

[0040] In a preferred variant of the first method, during at least a part of the duration of step b, preferably throughout the duration of step b, the heated product is subjected to a temperature that decreases at a constant rate over time.

[0041] The present invention also provides a second method for manufacturing a cathode active material, which comprises lithium, a metal other than lithium, and oxygen, wherein the metal has a composition M, and M consists of Ni with a content of x, Mn with a content of y, Co with a content of z, and A with a content of a. A is at least one chemical element other than Li, Ni, Mn, Co, and O. x, y, z, and a are expressed as molar contents, and x + y + z + a = 100 mol%. Wherein, x ≥ 70.0 mol%, 0 ≤ y ≤ 30.0 mol%, 0 ≤ z ≤ 30.0 mol%, and 0 ≤ a ≤ 5.0 mol%. The following continuous steps: a. Heating the precursor material at a heating temperature T1 between 750°C and 1000°C, preferably between 800°C and 950°C, more preferably between 850°C and 900°C, for a period t1 between 2 and 20 hours, preferably between 3 and 15 hours, even more preferably between 4 and 10 hours, to obtain a heated product; b. Cooling the heated product to a second temperature T2 between 650°C and 900°C, preferably between 700°C and 875°C, even more preferably between 750°C and 850°C, even more preferably between 775°C and 825°C, and maintaining the plateau temperature T2 for a time t2 between 5 and 20 hours, preferably between 7.5 and 17.5 hours, more preferably between 10 and 15 hours, to obtain a first cooled product; c. Further cooling the first cooled product, preferably to ambient temperature, to obtain a second cooled product, wherein the further cooling is preferably natural cooling; d. Milling and pulverizing the second cooled product; e. Heating the pulverized product at a temperature T3 between 200°C and 900°C to obtain a cathode active material. The present invention relates to a second method.

[0042] The inventors have found that the cooling profile significantly improves the product characteristics and results in the cathode active material of the present invention.

[0043] The cooling profile results in a cathode active material having a reduced LiOH content in accordance with the present invention. As a result, the cathode active material has better electrochemical performance. Furthermore, the cathode active material requires little or no post-treatment such as washing.

[0044] Also, compared with the conventional method, it does not require an excessive lithium source material or requires less excessive lithium source material.

[0045] A high heating temperature is required to obtain a monolithic product. At such a temperature, due to the natural thermodynamic equilibrium, a small amount of unreacted Li remains in the form of Li2O. When exposed to an atmosphere containing moisture, Li2O forms LiOH. Step b at a reduced temperature shifts the thermodynamic equilibrium. As a result, Li2O re-enters the cathode active material lattice, and thus the amount of lithium impurity compounds in the cathode active material decreases.

[0046] Also, the method enables the production of a cathode active material, preferably a cathode material, in accordance with the present invention.

[0047] The following preferred variations are applicable to both the first and second methods.

[0048] In a preferred variation, x, y, z, and a are measured by ICP-OES (Inductively Coupled Plasma).

[0049] In a preferred variation, ΔT defined as T1 - T2 is between 20°C and 400°C, preferably between 50°C and 350°C.

[0050] Milling In one embodiment, the cathode active material powder form is obtained by milling. Both wet milling and dry milling are in accordance with the present invention. Preferably, wet milling is performed in water or an aqueous solution.

[0051] In a preferred modification, the method includes heating the ball-milled positive electrode active material at a temperature T3 between 200 and 900 °C.

[0052] In a preferred modification, the method includes heating the ball-milled positive electrode active material at a temperature T3 between 200 and 500 °C for a duration of at least 30 minutes and at most 1200 minutes.

[0053] Positive electrode active material composition In a preferred modification, x ≥ 80.0 mol%, more preferably x ≥ 85.0 mol%, and even more preferably x ≥ 88.0 mol%.

[0054] In a preferred modification, x < 100.0 mol%, more preferably x < 98.5 mol%, and even more preferably x < 97.0 mol%.

[0055] In a preferred modification, (y + z) > 0, more preferably (y + z) > 1.5 mol%, and even more preferably (y + z) > 3.0 mol%.

[0056] In a preferred modification, x < 97.0 mol%, and y > 1.0 mol%, and z > 1.0 mol%.

[0057] In a preferred modification, the positive electrode active material is in powder form.

[0058] In a preferred modification, the molar ratio Li / (metal elements other than Li) in the positive electrode active material is at least 0.90 and at most 1.10.

[0059] In a preferred modification, the precursor contains an M source and an Li source, preferably both in an oxidized state.

[0060] In a preferred modification, y ≤ 15.0 mol%, more preferably y ≤ 7.5 mol%.

[0061] In a preferred modification, z ≤ 15.0 mol%, more preferably z ≤ 7.5 mol%.

[0062] In a preferred variant of the first method or the second method, the positive electrode active material is a positive electrode active material according to the present invention.

[0063] In a preferred embodiment of the positive electrode active material according to the present invention, the positive electrode active material is produced by the method according to the present invention.

Brief Description of the Drawings

[0064]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0065] Experimental tests used in the examples In the examples, the following analysis methods are used.

[0066] A) Particle Size Distribution (PSD) Analysis After dispersing the examples of the positive electrode active material powder described below in an aqueous medium, the PSD is measured using a Malvern Mastersizer 3000 equipped with a Hydro MV wet dispersion accessory. To improve the dispersion of the positive electrode active material powder examples, sufficient ultrasonic irradiation and stirring are applied, and an appropriate surfactant is introduced. D50 is defined herein as the particle size at 50% of the cumulative volume % distribution.

[0067] B) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) Analysis The examples of the positive electrode active materials described below are measured by inductively coupled plasma optical emission spectrometry (ICP-OES) using an Agillent ICP 720-OES. In an Erlenmeyer flask, 1 gram of the powder sample of each example is dissolved in 50 mL of high-purity hydrochloric acid. The flask is covered with a watch glass and heated on a hot plate at 380 °C until the sample is completely dissolved. After cooling to room temperature, the solution and the rinsing water in the Erlenmeyer flask are transferred to a 250 mL volumetric flask. Then, the volumetric flask is filled with DI water up to the 250 mL mark and subsequently homogenized. An appropriate amount of the solution is taken out with a pipette and transferred to a 250 mL volumetric flask for the second dilution. The volumetric flask is filled with an internal standard substance and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this solution is used for ICP-OES measurement. The contents of Ni, Mn, and Co are expressed as mol% of the total of these contents.

[0068] C) Coin cell test C1. Preparation of coin cell In the preparation of the positive electrode, a slurry containing a positive electrode active material powder, a conductive agent (Super P, Timcal), and a binder (KF#9305, Kureha) in a weight ratio of 96.5:1.5:2.0 is prepared by a high-speed homogenizer in a solvent (NMP, Mitsubishi). The homogenized slurry is spread on one side of an aluminum foil using a doctor blade coater with a 170 μm gap. The foil coated with the slurry is dried in an oven at 120 °C and then pressed using a calender tool. Then, this is dried again in a vacuum oven to completely remove the residual solvent in the electrode film. The coin cell is assembled in a glove box filled with argon. A separator (Celgard 2320) is placed between the positive electrode and a lithium foil piece used as the negative electrode. 1 M LiPF6 in EC / DMC (1:2) is used as the electrolyte and dropped between the separator and the electrode. Then, the coin cell is completely sealed to prevent electrolyte leakage.

[0069] C2. Test method The test method is the 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 cycle-tested at 25 °C using a Toscat-3100 computer-controlled galvanostatic cycling station (manufactured by Toyo).

[0070] The schedule uses a 1C current definition of 220 mA / g in the range of 4.3 V to 3.0 V / Li metal window. The capacity degradation rate (QF) is obtained by the following formula.

[0071]

Equation

[0072] In the formula, DQ1 is the discharge capacity at the first cycle, DQ7 is the discharge capacity at the seventh cycle, and DQ34 is the discharge capacity at the 34th cycle.

[0073]

Table 1

[0074] D) Surface base analysis In the measurement of the soluble base content by pH titration, two steps: (a) solution preparation, and (b) pH titration are carried out. The detailed description of each step is as follows: Step (a): Solution preparation: The powder is immersed in deionized water and stirred for 10 minutes in a sealed glass flask containing 100 mL of deionized water. The amount of the positive electrode active material powder is 4 grams. After stirring to dissolve the base, the suspension of the powder in water is filtered to obtain a transparent solution.

[0075] Step (b): pH titration: 90 mL of the clear solution prepared in step (a) is used for pH titration by using 0.1 M HCl. The flow rate is 0.5 mL / min, and the pH value is recorded every 3 seconds. The pH titration profile (pH value as a function of the added HCl) shows two distinct equivalence (or inflection) points. The first equivalence point around pH 7.4 (corresponding to the amount of HCl of EP1) results from the reaction of OH - and CO3 2- with H + . The second equivalence point around pH 4.7 (corresponding to the amount of HCl of EP2) results from the reaction of HCO3 - with H + . Assume that the base dissolved in deionized water is either LiOH (having an amount of 2*EP1 - EP2) or Li2CO3 (having an amount of 2*(EP2 - EP1)). The values obtained for LiOH and Li2CO3 are the result of the reaction of the surface with deionized water.

[0076] E) X-ray powder diffraction (XRD) E1) XRD measurement The X-ray diffraction patterns of the cathode active material powder examples described below are collected using a Rigaku X-ray diffractometer Ultima 4 with a Cu Kα radiation source emitting at a wavelength of 1.5418 Å (40 kV, 40 mA). The instrument configuration is set to a 1° Soller slit (SS), a 10 mm divergent height limiting slit (DHLS), a 1° divergence slit (DS), and a 0.3 mm reception slit (RS). The diameter of the goniometer is 185 mm. In XRD, the diffraction pattern is obtained in the range of 15 - 50° (2θ) at a scan speed of 3° / min and a step size of 0.02° / scan.

[0077] E2) X-ray diffractogram analysis The diffraction pattern obtained from E1) is analyzed in Origin 2018b Version b9.5.5.409 according to the following steps: 1. Subtract the baseline using endpoint weighting mode and 10% endpoint. 2. For the (003) peak, perform non-linear curve fitting using a Voigt line for the peak located at 2θ between 17.0° and 20.0°, and for the (104) peak, perform non-linear curve fitting using a Voigt line for the peak located at 2θ between 43.0° and 46.0°. The shape of the Voigt line follows the following equation:

[0078]

Equation

[0079] 3. For each of the (003) and (104) peaks, identify the maximum y-value from the obtained fitting curve. The intensity ratio (003) / (104) is obtained by dividing the maximum y-value of the (003) peak by the maximum y-value of the (104) peak.

[0080] F) Field Emission Scanning Electron Microscope (FE-SEM) Analysis The morphology of the positive electrode active material is analyzed by field emission scanning electron microscope (FE-SEM) technology. This measurement is performed using a JEOL JSM7100F under a high vacuum environment of 9.6×10 -5 Pa at 25°C.

[0081] [Examples] The present invention will be further described in the following examples.

[0082] Comparative Example 1 The positive electrode active material CEX1.1 is prepared by a solid-state reaction between a lithium source and a transition metal-based source precursor according to the following steps.

[0083] 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.90 Mn 0.05 Co 0.05 is prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0084] 2) Mixing: The precursor prepared in step 1) is mixed with LiOH and ZrO2 in an industrial blender to obtain a mixture containing 0.25 mol% Zr and having a lithium-to-metal ratio of 1.02.

[0085] 3) Heating: The mixture from step 2) is heated under an oxygen flow at a first temperature of 700 °C for a first duration of 10 hours, and then the temperature is raised to a second temperature of 840 °C for a second duration of 10 hours.

[0086] 4) Post-treatment: The heated powder from step 3) is pulverized and sieved to obtain the positive electrode active material CEX1.1.

[0087] CEX1.2 is prepared in the same manner as CEX1.1, except that the first temperature is 840 °C, the first duration is 10 hours, and then the temperature is decreased to a second temperature of 700 °C for a second duration of 2 hours. CEX1.2 follows the prior art KR20210018139 A.

[0088] Comparative Example 2 CEX2.1 is prepared in the same manner as CEX1.2, except that the second duration is 10 hours.

[0089] CEX2.2 is prepared in the same manner as CEX1.2, except that the second duration is 5 hours.

[0090] CEX2.3 is prepared in the same manner as CEX1.2, except that the first duration is 5 hours and the second duration is 10 hours.

[0091] CEX2.4 is prepared in the same manner as CEX1.2, except that the first duration is 5 hours and the second duration is 5 hours.

[0092] CEX2.5 is prepared in the same manner as CEX1.2, except that the second temperature is 660 °C and the second duration is 10 hours.

[0093] CEX2.6 is prepared in the same manner as CEX1.2, except that the second temperature is 740 °C and the second duration is 10 hours.

[0094] CEX2.7 is prepared in the same manner as CEX1.2, except that the second temperature is 760 °C and the second duration is 10 hours.

[0095] CEX2.8 is prepared in the same manner as CEX1.2, except that the second temperature is 660 °C and the second duration is 5 hours.

[0096] CEX2.9 is prepared in the same manner as CEX1.2, except that the second temperature is 740 °C and the second duration is 5 hours.

[0097] CEX2.10 is prepared in the same manner as CEX1.2, except that the second temperature is 760 °C and the second duration is 5 hours.

[0098] Comparative Example 3 The positive electrode active material CEX3 is obtained by a solid-phase reaction between a lithium source and a transition metal-based source precursor in the following method steps: 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.92 Mn 0.03 Co 0.05 is prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0099] 2) Mixing: The precursor prepared in step 1) and LiOH as a lithium source were homogeneously blended in an industrial blending apparatus at a lithium to metal M' (Li / M') ratio of 0.99.

[0100] 3) Heating: The mixture obtained from step 2) was heated at 820 °C for 10 hours under a stream of oxygen.

[0101] 4) Post-treatment: The heated powder from step 3) was pulverized and sieved to obtain CEX3.

[0102] Comparative Example 4 CEX4 was prepared in the same manner as CEX3, except that the heating in step 3) was carried out at a first temperature of 820 °C for a first duration of 10 hours and then the temperature was decreased to a second temperature of 700 °C for a second duration of 5 hours.

[0103] Comparative Example 5 The positive electrode active material CEX5 was prepared by a solid-state reaction between a lithium source and a transition metal-based source precursor according to the following steps.

[0104] 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.94 Mn 0.03 Co 0.03 was prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0105] 2) Mixing: The precursor prepared in step 1) was mixed with LiOH, ZrO2, and Al2O3 in an industrial blender to obtain a mixture containing 1500 ppm of Zr and 700 ppm of Al based on the total weight of Ni, Mn, and Co and having a lithium to metal ratio of 0.95.

[0106] 3) Heating: The mixture from step 2) is heated at a first temperature of 830 °C for 10 hours under an oxygen stream, and then the temperature is decreased to a second temperature of 710 °C for 10 hours.

[0107] 4) Post-treatment: The heated powder from step 3) is pulverized and sieved to obtain the positive electrode active material CEX5.

[0108] Comparative Example 6 The positive electrode active material CEX6.1 is prepared by a solid-phase reaction between a lithium source and a transition metal-based source precursor according to the following steps.

[0109] 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.88 Mn 0.05 Co 0.07 is prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0110] 2) Mixing: The precursor prepared from step 1) is mixed with LiOH and ZrO2 in an industrial blender to obtain a mixture containing 0.25 mol% of Zr based on the total molar content of Ni, Mn, and Co and having a lithium-to-metal ratio of 0.98.

[0111] 3) Heating: The mixture from step 2) is heated at a first temperature of 880 °C for 5 hours under an oxygen stream, and then the temperature is decreased to a second temperature of 760 °C for 7.5 hours.

[0112] 4) Post-treatment: The heated powder from step 3) is pulverized and sieved to obtain the positive electrode active material CEX6.1.

[0113] CEX6.2 is prepared in the same manner as CEX6.1, except that after the first heating at 880 °C, the temperature is slowly decreased to 700 °C at a rate of 30 °C / hour and then cooled to room temperature.

[0114] Comparative Example 7 The positive electrode active material CEX7.1 is obtained by a solid-phase reaction between a lithium source and a transition metal-based source according to the following steps.

[0115] 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.90 Mn 0.05 Co 0.05 is prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0116] 2) First mixing: The precursor prepared in step 1) is mixed with LiOH in an industrial blender to obtain a first mixture having a lithium-to-metal ratio of 1.06.

[0117] 3) Heating: The first mixture from step 2) is heated at 890 °C for 10 hours under an oxygen stream.

[0118] 4) Post-treatment: The heated powder from step 3) is pulverized and sieved to obtain the positive electrode active material CEX7.1.

[0119] 5) Wet bead mill pulverization: CEX7.1 is pulverized in a bead mill in a solution containing 0.5 mol% Co with respect to the total molar content of Ni, Mn, and Co in the first heated product, followed by drying and sieving to obtain a pulverized product. The weight ratio of solid to solution for bead mill pulverization was 6:4 and it was carried out for 20 minutes.

[0120] 6) Second mixing: The pulverized product from step 4) is mixed with H3BO3 as the B source and WO3 as the W source to obtain a third mixture containing 250 ppm of B and 2000 ppm of W.

[0121] 7) Heat treatment: The second mixture from step 5) was heated at 350 °C for 7 hours in an oxygen atmosphere to obtain CEX7.2 containing Ni, Mn, and Co with a ratio of Ni:Mn:Co of 0.89:0.05:0.06 as measured by ICP-OES. CEX7.2 has a D50 of 4 μm.

[0122] By wet milling in step 4), CEX7.2 is a monolithic powder.

[0123] Example 1 The positive electrode active material EX1 is obtained by a solid-state reaction between a lithium source and a transition metal-based source according to the following steps.

[0124] 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.90 Mn 0.05 Co 0.05 was prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0125] 2) First mixing: The precursor prepared from step 1) was mixed with LiOH and ZrO2 in an industrial blender to obtain a mixture containing 0.125 mol% of Zr and having a lithium-to-metal ratio of 1.02.

[0126] 3) Heating: The first mixture from step 2) was heated at a first temperature of 870 °C for 10 hours under an oxygen stream, and then the temperature was lowered to a second temperature of 700 °C and kept constant for 10 hours.

[0127] 4) Post-treatment: The heated powder from step 3) was pulverized and sieved to obtain the positive electrode active material EX1.1.

[0128] 5) Wet bead mill grinding: EX1.1 was bead mill ground in a solution containing 0.5 mol% Co with respect to the total molar content of Ni, Mn, and Co in the first heating product, followed by drying and sieving to obtain a ground product. The weight ratio of solid to solution for bead mill grinding was 6:4 and it was carried out for 20 minutes.

[0129] 6) Second mixing: The ground product from step 4) was mixed with H3BO3 as the B source and WO3 as the W source to obtain a third mixture containing 125 ppm of B and 1000 ppm of W.

[0130] 7) Heat treatment: The second mixture from step 5) was heated at 350 °C for 7 hours in an oxygen atmosphere to obtain EX1.2 containing Ni, Mn, and Co with a Ni:Mn:Co ratio of 0.89:0.05:0.05 as measured by ICP - OES. EX1.2 has a D50 of 4 μm.

[0131] Due to wet milling in step 4), EX1.2 is a monolithic powder.

[0132] Results The results of the experimental tests used for the examples described above are as follows.

[0133]

Table 2

[0134]

Table 3

[0135] Table 2 summarizes the heating conditions, compositions, and XRD peak analyses of the examples and comparative examples.

[0136] Compared with CEX2.1 to CEX2.10, which are cathode active materials containing the same amount of Ni, CEX1.1 prepared without a second heat treatment at low temperature contains a greater amount of LiOH. Furthermore, in XRD diffractogram analysis showing that the peak intensity ratio (003) / (104) of CEX2.1 to CEX2.10 exceeds 1.53, the maximum intensity of peak (003) is located between 2θ of 17.0° and 20.0°, and the maximum intensity of peak (104) is located between 2θ of 43.0° and 46.0°. The intensity ratio of (003) / (104) indicates the degree of structural irregularity, and the smaller this intensity ratio, the greater the structural irregularity due to cation mixing between Li atoms and Ni atoms. Furthermore, CEX1.2 prepared with a short t2 of 2 hours shows 1.43 wt% LiOH base, indicating that sufficient time at the second temperature is required to reduce both structural irregularity and surface base issues.

[0137] CEX2.1 to CEX2.4 were prepared by varying t1 and t2, indicating that a t2 of 10 hours is beneficial for reducing LiOH. On the other hand, an extended t2 is associated with a lower furnace throughput. CEX2.5 to CEX2.10 are cathode active materials prepared by varying the second heating time in the period of 5 to 10 hours. Comparative examples showing ΔT in the range of 50 to 300 °C are necessary to reduce LiOH impurities.

[0138] CEX3 and CEX4 are cathode active materials containing approximately 92 mol% Ni, prepared without and with the application of a second heat treatment at a reduced temperature, respectively. The comparison shows that the application of a second heat treatment at a reduced temperature reduces the LiOH base and maintains an XRD peak ratio of (003) / (104) higher than 1.53.

[0139] CEX7.1 and EX1.1 are, respectively, cathode active materials containing about 89 mol% Ni, prepared without and with the application of a second heat treatment at a reduced temperature. The comparison shows that the application of the second heat treatment at a reduced temperature reduces the LiOH base and maintains an (003) / (104) XRD peak ratio higher than 1.53.

[0140] Table 3 summarizes the heating conditions, composition, XRD peak analysis, and electrochemical properties of CEX7.2 and EX1.2. CEX7.2 and EX1.2 are, respectively, monolithic cathode active materials prepared from CEX7.1 and EX1.1 without and with the application of a second heat treatment. The comparison shows that the application of the second heat treatment reduces the LiOH base and maintains an (003) / (104) XRD peak ratio higher than 1.88. Furthermore, the capacity fade QF of EX1.2 is significantly improved compared to CEX7.2.

Claims

1. A positive electrode active material containing lithium, a metal other than lithium, and oxygen, wherein the metal has a composition M, M consists of Ni with a content of x, Mn with a content of y, Co with a content of z, and A with a content of a, A is at least one chemical element other than Li, Ni, Mn, Co, and O, x, y, z, and a are expressed as molar contents, and x + y + z + a = 100 mol%, - wherein, x ≥ 70.0 mol%, - 0 < y ≤ 30.0 mol%, - 0 < z ≤ 30.0 mol%, - 0 ≤ a ≤ 5.0 mol%, - the X-ray diffractogram of the positive electrode active material obtained from a Cu K-α X-ray radiation source has a (003) peak located at 2θ of 17.0° to 20.0° and a (104) peak located at 2θ of 43.0° to 46.0°, and the ratio ((maximum intensity of the (003) peak)) / ((maximum intensity of the (104) peak)) is at least 1.880, The positive electrode active material is monolithic.

2. The positive electrode active material according to claim 1, wherein the ratio ((maximum intensity of the (003) peak)) / ((maximum intensity of the (104) peak)) is at least 1.

900.

3. The positive electrode active material according to claim 1, wherein the ratio ((maximum intensity of the (003) peak)) / ((maximum intensity of the (104) peak)) is at least 1.

920.

4. The positive electrode active material according to any one of claims 1 to 3, wherein the molar ratio Li / (metal element other than Li) in the first positive electrode active material is at least 0.90 and at most 1.

10.

5. The positive electrode active material according to any one of claims 1 to 4, wherein x > 80.0 mol%.

6. The positive electrode active material according to any one of claims 1 to 5, wherein x < 98.5 mol%.

7. The positive electrode active material according to any one of claims 1 to 6, wherein (y + z) > 1.0 mol%.

8. The positive electrode active material according to any one of claims 1 to 7, wherein y > 0.5 mol% and z > 0.5 mol%.

9. The positive electrode active material according to any one of claims 1 to 8, wherein the positive electrode active material contains LiOH at a content of at most 0.20% by weight based on the total weight of the positive electrode active material, and the content of the LiOH is measured by acid-base titration.

10. A method for manufacturing the positive electrode active material according to any one of claims 1 to 9, comprising the following continuous steps: a. heating the precursor material at a heating temperature T1 between 750 °C and 1000 °C, preferably between 800 °C and 950 °C, more preferably between 850 °C and 925 °C, for a period t1 between 2 and 20 hours, preferably between 3 and 15 hours, even more preferably between 4 and 10 hours, to obtain a heated product; b. cooling the heated product to a second temperature T2 to obtain a first cooled product; c. further cooling the first cooled product to obtain a second cooled product, wherein the further cooling is preferably to ambient temperature and the further cooling is preferably natural cooling; d. ball-milling the second cooled product to obtain a milled product; e. heating the milled product at a temperature T3 between 200 °C and 900 °C to obtain the positive electrode active material, wherein step b cools the heated product to a second temperature T2 between 600 °C and 800 °C, preferably between 625 °C and 775 °C, even more preferably between 650 °C and 750 °C, even more preferably between 675 °C and 725 °C, to obtain a second heated product, and the average cooling rate is between 10 °C / h and 50 °C / h, preferably between 20 °C / h and 40 °C / h, more preferably between 25 °C / h and 35 °C / h; or step b cools the heated product to a second temperature T2 between 650 °C and 900 °C, preferably between 700 °C and 875 °C, even more preferably between 750 °C and 850 °C, even more preferably between 775 °C and 825 °C, and maintains the temperature T2 for a time t2 between 5 and 20 hours, preferably between 7.5 and 17.5 hours, even more preferably between 10 and 15 hours, in a manufacturing method.

11. The method according to claim 10, wherein ΔT=(T1 - T2), and 20 °C ≤ ΔT ≤ 400 °C, preferably 50 °C ≤ ΔT ≤ 350 °C.

12. The method according to claim 10 or 11, wherein 300 °C ≤ T3 ≤ 800 °C.

13. The method according to any one of claims 10 to 12, wherein the ball-milling is wet ball-milling in a ball-milling solution, and the ball-milling solution is preferably an aqueous solution, more preferably water.

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