Positive electrode active material for rechargeable lithium-ion battery

Abstract

A positive electrode active material containing 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, where x, y, z, and a are expressed as molar contents and x + y + z + a = 100%, wherein x ≥ 70.0%, 0 ≤ y ≤ 30.0%, 0 ≤ z ≤ 30.0%, 0 ≤ a ≤ 2.0 mol, and the X-ray diffraction pattern of the positive electrode active material 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 1.530. Positive electrode active material.

Description

Technical Field

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

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

[0003] Such a positive electrode active material preferably has a highly regular crystal structure. However, in practice, Ni 2+ may be present on the Li + sites in the crystal lattice, which deteriorates the battery performance, such as a high capacity drop during cycling.

[0004] The peak intensity ratio of the (003) / (104) peaks in the XRD diffractogram can serve 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, as is well known.

[0005] Such a positive electrode active material can be used as a positive electrode active material for a Li-based battery, but can also be regarded as an intermediate product that can undergo additional processing steps to improve its performance as a positive electrode active material.

Summary of the Invention

Means for Solving the Problems

[0006] The present invention relates to a cathode active material for a lithium rechargeable battery that improves the cathode active material and thus contains lithium, a metal other than lithium, and oxygen. The metal has a composition M, where 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 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°. The ratio ((maximum intensity of the (003) peak) / (maximum intensity of the (104) peak)) is at least 1.530. The object is to provide a cathode active material.

[0007] The advantage is that such a cathode active material has better performance than known cathode active materials.

[0008] Preferably, x, y, z, and a are measured by ICP-OES (inductively coupled plasma).

[0009] Preferably, the cathode active material is in powder form.

[0010] 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.

[0011] 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 a combination thereof.

[0012] 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 a combination thereof.

[0013] In a preferred embodiment, the ratio (maximum intensity of the (003) peak) / (maximum intensity of the (104) peak) is at least 1.540, more preferably at least 1.550.

[0014] Thereby, the beneficial effects of the present invention exist to a greater extent.

[0015] In a preferred embodiment, the molar ratio: Li / (metal element other than Li) in the positive electrode active material is at least 0.90 and at most 1.10.

[0016] In a preferred embodiment, the positive electrode active material is represented by formula (1): Li m Ni x Mn y Co z A a O2 Formula (1) Wherein m is at least 0.90 and at most 1.10.

[0017] In a preferred embodiment, ● x > 80.0 mol%, preferably x > 85.0 mol%, 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% and z > 0.5 mol%.

[0018] In a preferred embodiment, the positive electrode active material contains LiOH at a content of at most 1.40% by weight, more preferably at most 1.30% by weight, and even more preferably at most 1.20% by weight, based on the total weight of the positive electrode active material, and the content of LiOH is measured by acid-base (pH) titration as described herein.

[0019] LiOH impurities in the positive electrode active material significantly reduce the performance of the final battery, and therefore, it is necessary to reduce them as much as possible.

[0020] In a preferred embodiment, 0 ≤ a ≤ 2.0 mol%.

[0021] Preferably, the positive electrode active material is a powder, in other words, a plurality of particles.

[0022] More preferably, the positive electrode active material is a powder, and most of the particles therein are polycrystalline particles. Such a powder is also known as a polycrystalline particle-based powder.

[0023] When the particles are composed of 5 or more primary particles, preferably 10 or more primary particles, and more preferably 50 or more primary particles, as observed in the SEM image, they are considered to be polycrystalline. An example of polycrystalline particles is shown in Figure 3.

[0024] Since the primary particles can also be called granules, the primary particles can be distinguished from each other by observing the grain boundaries.

[0025] Preferably, in the SEM image of the positive electrode active material powder, at least 45 μm × at least 60 μm (i.e., at least 2700 μm 2) Preferably, at least 50%, more preferably at least 80% of the particles within a field of view of at least 100 μm × 100 μm (i.e., at least 10,000 μm 2 ) are polycrystalline.

[0026] The present invention further provides a first method for producing a positive electrode active material according to the present invention, comprising the following consecutive steps: a) heating a 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 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 obtaining a first cooled product with an average cooling rate 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; c) further cooling the first cooled product to obtain a positive electrode active material.

[0027] 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.

[0028] In a preferred variant of the first method, throughout the duration of step b, the heated product is subjected to a temperature that 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, and these terms must be understood in the context of what is actually possible in an industrial-scale furnace.

[0029] In one embodiment, the temperature of the method of the present invention is the set temperature of the furnace.

[0030] In a preferred variant of the first method, during at least part of the duration of step b, preferably during the entire duration of step b, the heating product is subjected to a temperature that decreases over time at a constant rate.

[0031] The present invention further relates to a second method for producing a positive electrode active material according to the present invention, the following consecutive steps: a) heating a 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 heating product; b) cooling the heating 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 cooling product; c) further cooling the first cooling product to obtain a positive electrode active material.

[0032] The inventors have found that the cooling profile significantly improves the product characteristics and results in the positive electrode active material of the present invention.

[0033] The cooling profile results in a positive electrode active material having a reduced LiOH content according to the present invention. As a result, the positive electrode active material has better electrochemical performance. Further, the positive electrode active material requires little or no post-treatment such as washing.

[0034] Also, compared with the conventional method, it does not require an excessive lithium source material or requires less excessive lithium source material.

[0035] Moreover, this method enables the production of a positive electrode active material, preferably a positive electrode material, according to the present invention.

[0036] The following preferred variations are applicable to both the first and second methods.

[0037] In a preferred variation, x, y, z, and a are measured by ICP-OES (Inductively Coupled Plasma).

[0038] In a preferred variation, ΔT defined as T1 - T2 is between 20°C and 400°C, preferably between 50°C and 350°C.

[0039] In a preferred variation, x ≥ 80.0 mol%, more preferably x ≥ 85.0 mol%, and even more preferably x ≥ 88.0 mol%.

[0040] In a preferred variation, x < 100.0 mol%, more preferably x < 98.5 mol%, and even more preferably x < 97.0 mol%.

[0041] In a preferred variation, (y + z) > 0, more preferably (y + z) > 1.5 mol%, and even more preferably (y + z) > 3.0 mol%.

[0042] In a preferred variation, x < 97.0 mol%, and y > 1.0 mol%, and z > 1.0 mol%.

[0043] In a preferred variation, the positive electrode active material is in powder form.

[0044] In a preferred variation, 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.

[0045] In a preferred variation, the precursor material contains an M source and a Li source, preferably both in an oxidized state.

[0046] In a preferred modification, y ≦ 15.0 mol%, more preferably, y ≦ 7.5 mol%.

[0047] In a preferred modification, z ≦ 15.0 mol%, more preferably, z ≦ 7.5 mol%.

[0048] In a preferred modification of the first method or the second method, the positive electrode active material is a positive electrode active material according to the present invention.

[0049] 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

[0050]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0051] Experimental tests used in the examples In the examples, the following analysis methods are used.

[0052] 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 a suitable surfactant is introduced. D50 is defined herein as the particle size at 50% of the cumulative volume% distribution.

[0053] B) Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) Analysis The examples of the positive electrode active material 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. Cover the flask with a watch glass and heat it on a hot plate at 380 °C until the sample is completely dissolved. After cooling to room temperature, transfer the solution and the rinsing water in the Erlenmeyer flask to a 250 mL volumetric flask. Then, fill the volumetric flask to the 250 mL mark with DI water and subsequently homogenize it completely. Pipette out an appropriate amount of the solution, transfer it to a 250 mL volumetric flask for the second dilution, fill the volumetric flask to the 250 mL mark with an internal standard substance and 10% hydrochloric acid, and then homogenize it. Finally, use this solution for ICP-OES measurement. The contents of Ni, Mn, and Co are expressed as mol% of the total of these contents.

[0054] 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). Spread the homogenized slurry on one side of an aluminum foil using a doctor blade coater with a 170 μm gap. Dry the foil coated with the slurry in an oven at 120 °C and then press it using a calendar tool. Then, dry it 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. Place a separator (Celgard 2320) between the positive electrode and a piece of lithium foil used as the negative electrode. Use 1 M LiPF6 in EC / DMC (1:2) as the electrolyte and drop it between the separator and the electrode. Then, completely seal the coin cell to prevent electrolyte leakage.

[0055] 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).

[0056] 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.

[0057]

Number

[0058] 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.

[0059]

Table 1

[0060] 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 clear solution.

[0061] 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 near pH 7.4 (corresponding to the amount of HCl at EP1) results from the reaction of OH - , and CO3 2- with H + . The second equivalence point near pH 4.7 (corresponding to the amount of HCl at 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.

[0062] 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 (40 kV, 40 mA) that emits at a wavelength of 1.5418 Å. 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) with a scan speed of 3° / min and a step size of 0.02° / scan.

[0063] 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 by endpoint weighting mode and 10% endpoint. 2. For the (003) peak, perform non-linear curve fitting using the 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 the Voigt line for the peak located at 2θ between 43.0° and 46.0°. The shape of the Voigt line follows the following equation:

[0064] [Number]

[0065] 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.

[0066] F) Scanning Electron Microscope (SEM) Analysis The morphology of the positive electrode active material can also be performed by a scanning electron microscope (SEM) using a benchtop device JEOL JCM-6100Plus. [Examples]

[0067] The present invention will be further described in the following examples.

[0068] 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.

[0069] 1. Coprecipitation: In a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia, the coprecipitation process is used to obtain a metal composition of Ni 0.90 Mn0.05 Co 0.05 Prepare a transition metal-based metal hydroxide precursor having

[0070] 2. Mixing: Mix the precursor prepared from step 1) 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.

[0071] 3. Heating: Heat the mixture from step 2) under an oxygen flow at a first temperature of 700 °C for a first duration of 10 hours, and then raise the temperature to a second temperature of 840 °C for a second duration of 10 hours.

[0072] 4. Post-treatment: Grind and sieve the heated powder from step 3) to obtain the cathode active material CEX1.1.

[0073] 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 Korean Patent Application Publication No. 20210018139(A).

[0074] Example 1 EX1.1 is prepared in the same manner as CEX1.2, except that the second duration is 10 hours.

[0075] EX1.2 is prepared in the same manner as CEX1.2, except that the second duration is 5 hours.

[0076] EX1.3 is prepared in the same manner as CEX1.2, except that the first duration is 5 hours and the second duration is 10 hours.

[0077] EX1.4 is prepared in the same manner as CEX1.2, except that the first duration is 5 hours and the second duration is 5 hours.

[0078] EX1.5 is prepared according to the same method as CEX1.2, except that the second temperature is 660 °C and the second duration is 10 hours.

[0079] EX1.6 is prepared according to the same method as CEX1.2, except that the second temperature is 740 °C and the second duration is 10 hours.

[0080] EX1.7 is prepared according to the same method as CEX1.2, except that the second temperature is 760 °C and the second duration is 10 hours.

[0081] EX1.8 is prepared according to the same method as CEX1.2, except that the second temperature is 660 °C and the second duration is 5 hours.

[0082] EX1.9 is prepared according to the same method as CEX1.2, except that the second temperature is 740 °C and the second duration is 5 hours.

[0083] EX1.10 is prepared according to the same method as CEX1.2, except that the second temperature is 760 °C and the second duration is 5 hours.

[0084] Comparative Example 2 The positive electrode active material CEX2 is obtained by a solid-state reaction between a lithium source and a transition metal-based source precursor in the following method steps.

[0085] 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) into which mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia are introduced.

[0086] 2. Mixing: The precursor prepared from Step 1) and LiOH as a lithium source are homogeneously blended in an industrial blending apparatus at a lithium to metal M (Li / M) ratio of 0.99.

[0087] 3. Heating: The mixture obtained from Step 2) is heated at 820 °C for 10 hours under a stream of oxygen.

[0088] 4. Post-treatment: The heated powder from Step 3) is pulverized and sieved to obtain CEX2.

[0089] Example 2 EX2 is prepared in the same manner as CEX2, except that the heating in Step 3) is carried out at a first temperature of 820 °C for a first duration of 10 hours, and then the temperature is lowered to a second temperature of 700 °C for a second duration of 5 hours.

[0090] Example 3 The positive electrode active material EX3 is prepared by a solid-state reaction between a lithium source and a transition metal-based source precursor according to the following steps.

[0091] 1. Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.94 Mn 0.03 Co 0.03 is prepared by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia.

[0092] 2. Mixing: The precursor prepared from Step 1) is mixed in an industrial blender with LiOH, ZrO2, and Al2O3 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.

[0093] 3. Heating: The mixture from Step 2) is heated at a first temperature of 830 °C for 10 hours under a stream of oxygen, and then the temperature is lowered to a second temperature of 710 °C for 10 hours.

[0094] 4. Post-treatment: The heated powder from Step 3) is pulverized and sieved to obtain the positive electrode active material EX3.

[0095] Example 4 The positive electrode active material EX4.1 is prepared by a solid-phase reaction between a lithium source and a transition metal-based source precursor according to the following steps.

[0096] 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.

[0097] 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% of Zr based on the total molar content of Ni, Mn, and Co and having a lithium-to-metal ratio of 0.98.

[0098] 3. Heating: The mixture from Step 2) is heated in an oxygen stream at a first temperature of 880 °C for 5 hours, and then the temperature is lowered to a second temperature of 760 °C for 7.5 hours.

[0099] 4. Post-treatment: The heated powder from Step 3) is pulverized and sieved to obtain the positive electrode active material EX4.1.

[0100] EX4.2 is prepared in the same manner as EX4.1 except that after the first heating at 880 °C, the temperature is slowly lowered to 700 °C at a rate of 30 °C / hour and then cooled to room temperature.

[0101] 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 according to the following steps.

[0102] 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.

[0103] 2. First mixing: The precursor prepared from step 1) is mixed with LiOH in an industrial blender to obtain a mixture having a lithium-to-metal ratio of 1.06.

[0104] 3. Heating: The first mixture from step 2) is heated at 890 °C for 10 hours under an oxygen stream.

[0105] 4. Post-treatment: The heated powder from step 3) is pulverized and sieved to obtain a positive electrode active material CEX3.1.

[0106] 5. Wet bead mill grinding: CEX3.1 is ground 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 ground product. The weight ratio of solid to solution in bead mill grinding is 6:4 and it is carried out for 20 minutes.

[0107] 6. Second mixing: The ground 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.

[0108] 7. Heat treatment: The second mixture from step 5) is heated at 350 °C for 7 hours in an oxygen atmosphere to obtain CEX3.2 containing Ni, Mn, and Co with a ratio of Ni:Mn:Co of 0.89:0.05:0.06 as measured by ICP-OES. CEX3.2 has a D50 of 4 μm.

[0109] Example 5 The positive electrode active material EX5 is obtained by a solid-phase reaction between a lithium source and a transition metal-based source according to the following steps.

[0110] 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.

[0111] 2. First mixing: The precursor prepared from step 1) is 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.

[0112] 3. Heating: The first mixture from step 2) is heated in an oxygen stream at a first temperature of 870 °C for 10 hours, then the temperature is lowered to a second temperature of 700 °C and kept constant for 10 hours.

[0113] 4. Post-treatment: The heated powder from step 3) is pulverized and sieved to obtain the positive electrode active material EX5.1.

[0114] 5. Wet bead mill pulverization: The heated product from step 3) is pulverized in a bead mill in a solution containing 0.5 mol% of Co based on 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 is 6:4 and it is carried out for 20 minutes.

[0115] 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 125 ppm of B and 1000 ppm of W.

[0116] 7. Heat treatment: The second mixture from step 5) was heated at 350 °C for 7 hours in an oxygen atmosphere to obtain EX5.2 containing Ni, Mn, and Co with a Ni:Mn:Co ratio of 0.89:0.05:0.05 as measured by ICP-OES. EX5.2 has a D50 of 4 μm.

[0117] Results The results of the experimental tests used for the examples described above are as follows.

[0118] [Table 2]

[0119] [Table 3]

[0120] Table 2 summarizes the heating conditions, compositions, and XRD peak analysis of the examples and comparative examples.

[0121] Compared with EX1.1 - EX1.10, which are cathode active materials containing the same amount of Ni, CEX1.1 prepared without the second heat treatment at low temperature contains a larger amount of LiOH. Furthermore, in the XRD diffractogram analysis showing that the peak intensity ratio (003) / (104) of EX1.1 - EX1.10 exceeds 1.53, the maximum intensity of peak (003) is located between 2θ = 17.0° and 20.0°, and the maximum intensity of peak (104) is located between 2θ = 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% of LiOH base, indicating that sufficient time at the second temperature is required to reduce both the structural irregularity and the problem of surface base.

[0122] EX1.1 to EX1.4 were prepared by varying t1 and t2, and it is shown 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. EX1.5 to EX1.10 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 for reducing LiOH impurities.

[0123] CEX2 and EX2 are cathode active materials containing about 92 mol% of 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 (003) / (104) XRD peak ratio higher than 1.53.

[0124] CEX3.1 and EX5.1 are cathode active materials containing about 89 mol% of 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 (003) / (104) XRD peak ratio higher than 1.53.

[0125] Table 3 summarizes the heating conditions, compositions, XRD peak analysis, and electrochemical properties of CEX3 and EX5. CEX3 and EX5 are cathode active materials prepared without and with the application of a second heat treatment, respectively. The comparison shows that the application of a 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 EX5 is significantly improved compared to CEX3.

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 = 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 1.530, the positive electrode active material contains LiOH at a content of at most 1.40% 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, a positive electrode active material.

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.

550.

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 most 3.

000.

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 positive electrode active material is at least 0.90 and at most 1.

10.

5. The positive electrode active material is represented by formula (1): Li ｍ Ni ｘ Mn ｙ Co ｚ A ａ O ２ Formula (1) wherein m is at least 0.90 and at most 1.10, the positive electrode active material according to any one of claims 1 to 4.

6. The positive electrode active material according to any one of claims 1 to 5, wherein x > 85.0 mol%.

7. The positive electrode active material according to any one of claims 1 to 6, wherein x > 88.0 mol%.

8. The positive electrode active material according to any one of claims 1 to 7, wherein x < 98.5 mol%.

9. The positive electrode active material according to any one of claims 1 to 8, wherein (y + z) > 1.0 mol%.

10. The positive electrode active material according to any one of claims 1 to 9, wherein y > 0.5 mol% and z > 0.5 mol%.

11. The positive electrode active material contains LiOH at a content of at most 1.30% 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. The positive electrode active material according to any one of claims 1 to 10.

12. The positive electrode active material contains LiOH at a content of at most 1.20% 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. The positive electrode active material according to any one of claims 1 to 11.

13. The positive electrode active material according to any one of claims 1 to 12, wherein the positive electrode active material is polycrystalline.

14. A method for manufacturing the positive electrode active material according to any one of claims 1 to 13, comprising the following continuous steps: a) Heating a precursor material containing an M source and a Li source 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 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. The manufacturing method.

15. ΔT = (T1 - T2), and 20 °C ≤ ΔT ≤ 400 °C, preferably 50 °C ≤ ΔT ≤ 350 °C, more preferably 300 °C ≤ T3 ≤ 800 °C. The method according to claim 14.

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