Lithium nickel-based composite oxide as a positive electrode active material for a rechargeable lithium-ion battery

Abstract

The present invention relates to a lithium nickel-based oxide positive electrode active material for lithium ion secondary batteries, comprising lithium transition metal-based oxide particles containing zirconium, suitable for electric vehicle and hybrid electric vehicle applications, and a preparation method for this positive electrode material.

Description

Technical Field

[0001] The present invention relates to a lithium nickel-based oxide cathode active material for a lithium-ion secondary battery (LIB) containing lithium transition metal-based oxide particles containing zirconium, which is suitable for use in electric vehicles (EV) and hybrid electric vehicles (HEV), and a preparation method for this cathode material.

Background Art

[0002] The cathode active material is defined as a material that is electrochemically active in the cathode. It should be understood that the active material is a material that can capture and release Li ions when exposed to a voltage change over a predetermined period.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, when used in a full cell, it is an object of the present invention to provide a cathode active material in which one or more characteristics such as no expansion (i.e., an increase in the thickness of the full cell) or a reduction in expansion, an increase in cycle life, and an increase in life cycle are improved.

Means for Solving the Problems

[0004] This object is a cathode active material for a lithium-ion battery, containing Li, M', and O, where M' is Ni with a content x of 60.0 mol% to 95.0 mol% with respect to M', Co with a content y of 0 ≤ y ≤ 40.0 mol% with respect to M', Mn with a content z of 0 ≤ z ≤ 70.0 mol% with respect to M', W with a content a of 0 ≤ a ≤ 4.0 mol% with respect to M', Zr with a content b of 0.01 mol% to 0.20 mol% with respect to M', For M', elements other than Li, O, Ni, Co, Mn, W, Al, S, and Zr with a content c of 0 ≦ c ≦ 2.0 mol%, and S with a content d of 0.01 ≦ d ≦ 3.0 mol% for M', Al with a content e of 0 ≦ e ≦ 2.0 mol% for M' consisting of x, y, z, a, b, c, d, and e are measured by ICP, x + y + z + a + b + c + d + e is 100.0 mol%, The positive electrode active material is

[0005]

Number

[0006] The content S of S defined as A having The positive electrode active material has the content S of S determined by XPS analysis B having S B S is represented as the molar fraction compared with the total of the molar fractions of Co, Mn, Ni, W, and S measured by XPS analysis, Ratio S B / S A > 1.0, is achieved by providing a positive electrode active material.

[0007] In the framework of the present invention, ppm means parts per million for the unit of concentration and represents 1 ppm = 0.0001 wt%.

[0008] Another aspect is a positive electrode active material powder for a lithium-ion rechargeable battery, wherein the positive electrode active material contains Li, M', and O, and M' is Ni with a content x of 60.0 mol% to 95.0 mol% for M', Co with a content y of 0 ≦ y ≦ 40.0 mol% for M', Mn with a content z of 0 ≦ z ≦ 70.0 mol% for M', W with a content a of 0.01 mol% to 4.0 mol% for M', Zr having a content b of 0.01 mol% to 0.20 mol% with respect to M', elements other than Li, O, Ni, Co, Mn, W, Al, S and Zr having a content c of 0 ≦ c ≦ 2.0 mol% with respect to M', and S having a content d of 0.00 ≦ d ≦ 3.0 mol% with respect to M', Al having a content e of 0 ≦ e ≦ 2.0 mol% with respect to M' comprising, x, y, z, a, b, c, d and e are measured by ICP, x + y + z + a + b + c + d + e is 100.0 mol%, the positive electrode active material has a content WA of W defined as a / ((x + y + z + a + d)), the positive electrode active material has a content WB of W determined by XPS analysis, and WB is expressed as a molar fraction compared to the total molar fraction of Co, Mn, Ni, W and S measured by XPS analysis, the ratio WB / WA > 1.0, is a positive electrode active material powder.

[0009] The present invention relates to the following embodiments.

[0010] Embodiment 1 In the first aspect, the present invention contains Li, M' and O, and M' is Ni having a content x of 60.0 mol% to 95.0 mol% with respect to M', Co having a content y of 0 ≦ y ≦ 40.0 mol% with respect to M', Mn having a content z of 0 ≦ z ≦ 70.0 mol% with respect to M', W having a content a of 0 ≦ a ≦ 4.0 mol% with respect to M', Zr having a content b of 0.01 mol% to 0.20 mol% with respect to M', elements other than Li, O, Ni, Co, Mn, W, Al, S and Zr having a content c of 0 ≦ c ≦ 2.0 mol% with respect to M', and S having a content d of 0.01 ≦ d ≦ 3.0 mol% with respect to M', Al having a content e of 0 ≦ e ≦ 2.0 mol% with respect to M' comprising, x, y, z, a, b, c, d and e are measured by ICP, x + y + z + a + b + c + d + e is 100.0 mol%, the positive electrode active material has

[0011] [Number]

[0012] the content S of S defined as A having, the positive electrode active material has the content S of S determined by XPS analysis B having S B S is represented as the molar fraction compared with the total molar fraction of Co, Mn, Ni, W and S measured by XPS analysis, ratio S B / S A > 1.0, relates to a positive electrode active material for a lithium ion battery.

[0013] Preferably, S B / S A > 2.0.

[0014] Preferably, the positive electrode material of the present invention contains 0.01 mol% ≦ a ≦ 4.0 mol%, and the positive electrode active material has

[0015] [Number]

[0016] the content W of W defined as A having, the positive electrode active material has the content W of W determined by XPS analysis B having W B W is represented as the molar fraction compared with the total molar fraction of Co, Mn, Ni, W and S measured by XPS analysis, ratio W B / W A > 1.0.

[0017] Preferably, Ni has a content of x ≧ 65.0 mol%, more preferably x ≧ 70.0 mol%, even more preferably x ≧ 75.0 mol%, and most preferably x ≧ 80.0 mol% with respect to M'.

[0018] Preferably, Ni has a content of x ≦ 93.0 mol%, more preferably x ≦ 91.0 mol%, and most preferably x ≦ 90.0 mol% with respect to M'.

[0019] Preferably, Co has a content of y > 0 mol%, more preferably y ≧ 1.0 mol%, and even more preferably y ≧ 5.0 mol% with respect to M'.

[0020] Preferably, Co has a content of y ≦ 35 mol%, more preferably y ≦ 30.0 mol%, and most preferably y ≦ 20.0 mol% with respect to M'.

[0021] Preferably, Mn has a content of z > 0 mol%, more preferably z ≧ 1.0 mol, and even more preferably z ≧ 5.0 mol% with respect to M'.

[0022] Preferably, Mn has a content of z ≦ 65 mol%, more preferably z ≦ 60.0 mol%, and most preferably z ≦ 50.0 mol% with respect to M'.

[0023] In another embodiment, Ni with a content of x is 70 mol% to 91 mol% with respect to M', Co with a content of y is 0.0 mol% to 30.0 mol% with respect to M', and Mn with a content of z is 0.0 mol% to 50.0 mol% with respect to M'.

[0024] In another embodiment, W with a content of a is 0.10 mol% to 3.00 mol% with respect to M'.

[0025] Embodiment 2 In a second aspect, preferably in accordance with Embodiment 1, the present invention provides a positive electrode active material powder for a lithium-ion rechargeable battery, wherein the positive electrode active material contains Li, M', and O, and M' is Ni with a content x of 60.0 mol% to 95.0 mol% relative to M', Co with a content y of 0 ≤ y ≤ 40.0 mol% relative to M', Mn with a content z of 0 ≤ z ≤ 70.0 mol% relative to M', W with a content a of 0.01 mol% to 4.0 mol% relative to M', Zr with a content b of 0.01 mol% to 0.20 mol% relative to M', an element other than Li, O, Ni, Co, Mn, W, Al, S, and Zr with a content c of 0 ≤ c ≤ 2.0 mol% relative to M', and S with a content d of 0.00 ≤ d ≤ 3.0 mol% relative to M', Al with a content e of 0 ≤ e ≤ 2.0 mol% relative to M' and is composed of wherein x, y, z, a, b, c, d, and e are measured by ICP, x + y + z + a + b + c + d + e = 100.0 mol%, the positive electrode active material has

[0026]

Number

[0027] a content W of W defined as A and has a content W of W of the positive electrode active material determined by XPS analysis B wherein W B is expressed as a molar fraction compared with the total molar fraction of Co, Mn, Ni, W, and S measured by XPS analysis, the ratio W B / W A > 1.0, relating to the positive electrode active material powder.

[0028] Preferably, the positive electrode active material contains 0.01 mol% ≦ d ≦ 3.0 mol%, and the positive electrode active material

[0029]

Number

[0030] has a content S of S defined as A and the positive electrode active material has a content S of S determined by XPS analysis B and S B is expressed as a molar fraction compared with the total molar fraction of Co, Mn, Ni, W and S measured by XPS analysis, Ratio S B / S A > 1.0.

[0031] Preferably, Ni has a content of x ≧ 65.0 mol%, more preferably x ≧ 70.0 mol%, even more preferably x ≧ 75.0 mol%, and most preferably x ≧ 80.0 mol% with respect to M'.

[0032] Preferably, Ni has a content of x ≦ 93.0 mol%, more preferably x ≦ 91.0 mol%, and most preferably x ≦ 90.0 mol% with respect to M'.

[0033] Preferably, Co has a content of y> 0 mol%, more preferably y ≧ 1.0 mol%, and even more preferably y ≧ 5.0 mol% with respect to M'.

[0034] Preferably, Co has a content of y ≦ 35 mol%, more preferably y ≦ 30.0 mol%, and most preferably y ≦ 20.0 mol% with respect to M'.

[0035] Preferably, Mn has a content of z> 0 mol%, more preferably z ≧ 1.0 mol, and even more preferably z ≧ 5.0 mol% with respect to M'.

[0036] Preferably, Mn has a content of z ≤ 65 mol%, more preferably z ≤ 60.0 mol%, and most preferably z ≤ 50.0 mol% with respect to M'.

[0037] In another embodiment, Ni with a content of x is 70 mol% to 91 mol% with respect to M', Co with a content of y is 0.0 mol% to 30.0 mol% with respect to M', and Mn with a content of z is 0.0 mol% to 50.0 mol% with respect to M'.

[0038] In another embodiment, W with a content of a is 0.10 mol% to 3.00 mol% with respect to M'.

[0039] Embodiment 3 In the third embodiment, preferably according to Embodiments 1 to 2, this positive electrode active material contains Zr with a content of b of 0.10 mol% to 0.2 mol% with respect to M'.

[0040] Embodiment 4 In the fourth embodiment, preferably according to Embodiments 1 to 3, this positive electrode active material contains Al with a content of e of 0.10 mol% to 2.00 mol% with respect to M'.

[0041] Embodiment 5 In the fifth embodiment, preferably according to Embodiments 1 to 4, this positive electrode active material contains elements other than Li, O, Ni, Co, Mn, W, Al, and S, and contains at least one element from the group consisting of B, Ba, Ca, Cr, F, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, and Zn.

[0042] In another embodiment, preferably, the positive electrode active material according to any one of the preceding claims, wherein the element other than Li, O, Ni, Co, Mn, W, Al, and S is at least one element from the group consisting of B, Ba, Ca, Cr, F, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, and Zn.

[0043] Embodiment 6 In a sixth aspect, the present invention also provides a process for manufacturing a positive electrode active material according to any one of Embodiments 1 to 5, comprising: preparing a lithium transition metal oxide compound; obtaining a mixture by mixing the lithium transition metal oxide compound with a sulfur source and water; and heating the mixture in an oxidizing atmosphere in a furnace at a temperature of 350°C to less than 500°C to obtain a positive electrode active material. The process includes the steps above.

[0044] In one embodiment, preferably, in the process according to the present invention, a tungsten source is added together with the sulfur source during the mixing step.

[0045] Preferably, the tungsten source can be selected from tungsten oxide and lithium tungstate, but is not limited thereto.

[0046] Preferably, the W content is 100 ppm to 10,000 ppm based on the total weight of the positive electrode active material. More preferably, the tungsten content is 1,000 ppm to 8,000 ppm.

[0047] Preferably, the sulfur source is selected from Al 2 (SO 4 ) 3 , sulfates and / or H 2 SO 4 , more preferably Al 2 (SO 4 ) 3 , but is not limited thereto.

[0048] Preferably, the S content is 350 ppm to 3,500 ppm based on the total weight of the positive electrode active material. More preferably, the S content is 400 ppm to 3,000 ppm.

[0049] Preferably, the heating temperature is at most 450°C.

[0050] Preferably, the heating time ranges from 1 hour to 20 hours.

[0051] Preferably, the lithium transition metal oxide indicator material is prepared from a lithiation process, i.e., a process of heating a mixture of a transition metal-containing precursor and a lithium source at a temperature of at least 500 °C.

[0052] Preferably, the transition metal-containing precursor contains nickel, cobalt and / or manganese. Typically, the transition metal-containing precursor is prepared by precipitation by a method known in the art.

[0053] Preferably, in this embodiment, the lithium transition metal oxide contains Zr, and the source of Zr is mixed with the Li source during lithiation.

[0054] Preferably, the source of zirconium can be selected from zirconium oxide and lithium zirconate, but is not limited thereto.

[0055] Preferably, the content of Zr is 100 ppm to 2500 ppm based on the total weight of the positive electrode active material. More preferably, the Zr content is 200 ppm to 2200 ppm.

[0056] Embodiment 7 In the seventh aspect, the present invention relates to the use of the positive electrode active material according to any one of the preceding embodiments 1 to 6 in a battery.

[0057] This battery is a rechargeable lithium-ion battery including a cathode, an anode, a separator and an electrolyte. Preferably, the electrolyte is a non-aqueous liquid electrolyte. The positive electrode active material in this invention is used for the positive electrode.

[0058] The present invention also relates to the use of the battery according to the present invention in an electric vehicle or in a hybrid electric vehicle.

Mode for Carrying Out the Invention

[0059] In the following embodiments for carrying out the invention, preferred embodiments are described to enable the implementation of the present invention. Although the present invention is described with reference to these specific preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. The present invention includes many alternatives, modifications and equivalents that are apparent from the following embodiments for carrying out the invention and the consideration of the accompanying drawings.

[0060] A) ICP analysis The Li, Ni, Mn, Co, S, W, Al and Zr contents of the positive electrode active material powder are measured by the inductively coupled plasma (ICP) method using an Agillent ICP 720-ES. In an Erlenmeyer flask, 2 grams of the product powder sample is dissolved in 10 mL of high-purity hydrochloric acid. The flask is covered with glass and heated on a hot plate at 380 °C until the precursor is completely dissolved. After cooling to room temperature, the solution in the Erlenmeyer flask is poured into a 250 mL volumetric flask. Then, the volumetric flask is filled with deionized water up to the 250 mL mark and subsequently thoroughly homogenized. An appropriate amount of the solution is taken out with a pipette, transferred to a 250 mL volumetric flask for a second dilution, and the volumetric flask is filled with an internal standard substance and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, 50 mL of this solution is used for ICP measurement.

[0061] B) Particle size distribution 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 equipped with a Hydro MV wet dispersion accessory after dispersing each of the powder samples in an aqueous medium. To improve the dispersion of the powder, sufficient ultrasonic irradiation and stirring are applied and an appropriate surfactant is introduced. D50 is defined as the particle size at 50% of the cumulative volume % distribution obtained from the Malvern Mastersizer 3000 by Hydro MV measurement.

[0062] C) Full cell test C1) Preparation of full cell A 2000 mAh pouch cell is prepared as follows: The positive electrode active material powder, Super - P as the positive electrode conductive agent (Super - P, Timcal, (Imerys Graphite & Carbon)), and polyvinylidene fluoride (PVDF S5130, Solvay) as the positive electrode binder are added to N - methyl - 2 - pyrrolidone (NMP) as the dispersion medium, resulting in a mass ratio of positive electrode active material powder:positive electrode conductive agent:super P:positive electrode binder of 95 / 3 / 2. Then, the mixture is kneaded to prepare a positive electrode mixture slurry. Next, the obtained positive electrode mixture slurry is applied to both sides of a positive electrode current collector made from an aluminum foil with a thickness of 20 μm. The width of the coating area is 88.5 mm and the length is 425 mm. The typical loading weight of the positive electrode active material is about 15.3 ± 1 mg / cm 2 is carried out. Then, the electrode is dried and calendared using a pressure of 4.5 MPa. In addition, an aluminum plate serving as the positive electrode current collector tab is arc - welded to the end of the positive electrode.

[0063] A commercially available negative electrode is used. Specifically, a mixture of natural graphite, carbon, sodium carboxymethyl cellulose (CMC), and styrene - butadiene - rubber (SBR) at a mass ratio of 95.5 / 1 / 1.5 / 2 is applied to both sides of a copper foil. A nickel plate serving as the negative electrode current collector tab is arc - welded to the end of the negative electrode. The typical loading weight of the negative electrode active material is about 10 ± 1 mg / cm 2 is carried out.

[0064] Lithium hexafluorophosphate (LiPF in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio of 1:1:16 ) By dissolving the salt at a concentration of 1.2 mol / L, a non-aqueous electrolyte is obtained. The non-aqueous electrolyte contains, as additives, 1.0 wt% of lithium difluorophosphate (LiPO 2 F 2 ) and 1.0 wt% of vinylene carbonate (VC).

[0065] To obtain a spirally wound electrode assembly, a positive electrode sheet, a negative electrode sheet, and a sheet of a microporous polymer separator (13 μm) inserted therebetween are spirally wound using a winding core rod. Then, the assembly and the electrolyte are placed in an aluminum laminated pouch in a dry room with a dew point of -50°C to prepare a flat pouch-type lithium secondary battery. The designed capacity of the secondary battery is 2000 mAh when charged up to 4.20V. In the full cell test procedure, a 1C current definition of 2000 mA / g is used.

[0066] C2) Expansion test A 2000 mAh pouch-type battery prepared by the above preparation method is fully charged up to 4.2V and placed in an oven heated to 90°C, where it is kept for 20 hours. The charged positive electrode reacts with the electrolyte at 90°C to generate gas. The generated gas causes expansion. After 20 hours, the increase in thickness ((thickness after storage - thickness before storage) / thickness before storage × 100%) is measured.

[0067] C3) Cycle life test A. Preliminary charging and formation The prepared dry battery is impregnated in the non-aqueous electrolyte solution at room temperature for 8 hours. The battery is preliminarily charged at a current of 0.25C up to 15% of the theoretical capacity and aged at room temperature for 1 day. Then, using a pressure of -760 mmHg, the battery is degassed for 30 seconds and the aluminum pouch is sealed.

[0068] In the CC mode (constant current), the battery is charged at a current of 0.2C up to 4.2V or 4.3V, and in the CV mode (constant voltage), it is charged until the cut-off current of C / 20 is reached. In the CC mode, the battery is discharged at a current of 0.2C until it drops to 2.7V. Then, in the CC mode, it is fully charged at a current of 0.50C up to 4.2V or 4.3V, and in the CV mode, until the cut-off current of C / 20 is reached.

[0069] After that, in the CC mode, the cell is discharged at a current of 0.50C until it drops to 2.7V. Again, in the CC mode, it is charged at a current of 0.5C up to 4.2V or 4.3V, and in the CV mode, until the cut-off current of C / 20 is reached. The final charging process is carried out at 25°C.

[0070] B. Cycle Life Test The lithium secondary full cell batteries are continuously charged and discharged at 45°C under the following conditions to determine their charge-discharge cycle performance.

[0071] In the CC mode, charging is carried out at a 1C rate up to 4.2V, and then in the CV mode, until the cut-off current of C / 20 is reached.

[0072] Then, the cell is rested for 10 minutes.

[0073] In the CC mode, discharging is carried out at a 1C rate until it drops to 2.7V.

[0074] Then, the cell is rested for 10 minutes.

[0075] The charge-discharge cycle is continued up to 800 cycles or 1000 cycles. Every 100 cycles, in the CC mode, discharging is carried out at a 0.1C rate until it drops to 2.7V.

[0076] The retention capacity in the nth cycle is calculated as the ratio of the discharge capacity obtained in the nth cycle to that in the first cycle.

[0077] The cycle life is defined as the number of charge-discharge cycles at the point when the capacity has decreased to 80%.

[0078] D) X-ray photoelectron spectroscopy (XPS) analysis In the present invention, X-ray photoelectron spectroscopy (XPS) is used to analyze the surface of the positive electrode active material powder particles. In XPS measurement, the signal is obtained from the uppermost part of the sample, that is, the first few nanometers (for example, 1 nm to 10 nm) of the surface layer. Therefore, all elements measured by XPS are contained in the surface layer.

[0079] For the surface analysis of the positive electrode active material powder particles, XPS measurement is performed using a Thermo K-α+ spectrometer (Thermo Scientific, https: / / www.thermofisher.com / order / catalog / product / IQLAADGAAFFACVMAHV). Monochromatic Al Kα radiation (hv = 1486.6 eV) is used at a spot size of 400 μm and a measurement angle of 45°. An extensive survey scan for identifying the elements present on the surface is performed at a pass energy of 200 eV. The C1s peak having the maximum intensity (concentrating) at a binding energy of 284.8 eV is used as the calibration peak position after data collection. Then, for each identified element, an accurate narrow scan is scanned at least 10 times at 50 eV to determine the accurate surface composition.

[0080] Curve fitting is performed by CasaXPS version 2.3.19PR1.0 (Casa Software, http: / / www.casaxps.com / ) using Shirley-type background processing and Scofield sensitivity coefficients. The fitting parameters are according to Table 1a. The line shape GL(30) is the Gaussian / Lorentz product formula in a 70% Gaussian line and 30% Lorentz line. LA(α, β, m) is an asymmetric line shape, where α and β define the tail spread of the peak and m defines the width.

[0081]

Table 1

[0082] For the Co, W, and S peaks, constraints regarding each defined peak are set according to Table 1b. W5p3 is not quantified.

[0083]

Table 2

[0084] The surface contents of S and W determined by XPS are expressed as mole fractions obtained by dividing S and W on the surface of the particles by the total content of Ni, Mn, Co, and W on the surface. These are calculated as follows.

[0085]

Equation

[0086] The present invention will be further illustrated by the following (non-limiting) examples.

[0087] Comparative Example 1.1 (CEX1.1) CEX1.1 was obtained through a solid-state reaction between a lithium source and a transition metal-based source precursor, which was carried out as follows. 1. Preparation of the precursor: The precipitation process of the precursor was carried out in a reactor with a liquid volume of 10 L, using an overflow pipe and a 400 W impeller motor. An impeller with a diameter of 10 cm was stirred at 800 RPM. The reactor had four baffles that enabled intense stirring. A nitrogen gas flow of 50 L / h was applied above the liquid surface to avoid oxidation caused by intense stirring. Three solutions containing nickel sulfate, manganese sulfate, and cobalt sulfate (NiSO 4 , MnSO 4 , CoSO 4 ) with a total metal concentration of 110 g / L were prepared and mixed to form a mixed MeSO 4A solution was obtained (where Me consists of Ni, Mn, and Co). The first solution had a molar ratio of Ni:Mn:Co of 87:5:8, and the second solution had a molar ratio of 0:5:95. A solution of 400 g / L NaOH and a 25% undiluted ammonia solution were used. The total metal composition of the precursor was Ni 0.85 Mn 0.05 Co 0.10 and was prepared in processes S1 - S3. a. Preparation of S1 - seeds: Ni 0.87 Mn 0.05 Co 0.08 (OH) 2 The seed precursor was prepared using typical co - precipitation in a continuous stirred tank reactor (CSTR) with a specific residence time of 6 hours. At the start, the reactor was filled with water and ammonia to obtain an ammonia solution of 15 g / L inside. The temperature inside the reactor was 60 °C. After filling the reactor with the starting solution, the ratio of ammonia to metal was kept at 1:1 and the pH was kept around 11.7, and various reagents (MeSO 4 solution, NaOH solution, NH 3 solution) were simultaneously pumped into the reactor at different injection points. During the precipitation reaction, there should be more than 2 OH - ions for each metal ion in the solution. After 24 hours, the reactor was in a steady state, D50 was 5 μm - 20 μm, and the slurry from the overflow was collected. The precipitated metal hydroxide was washed and filtered under a protective atmosphere to remove dissolved salts and ammonia. 200 grams of the wet cake was repulped in 1 L of water and treated by mechanical grinding with a ball mill. This treatment reduced the D50 size to less than 2 μm. b. Preparation of S2 - core particles: Ni 0.87 Mn 0.05 Co 0.08 (OH) 2 The core precursor was prepared using modified co - precipitation in a continuous stirred tank reactor (CSTR) with a specific or average residence time of 3 hours. MeSO 4The first solution composition was used. At the start, the reactor was filled with water and ammonia to obtain an ammonia solution of 15 g / L inside. The temperature inside the reactor was 60 °C. After filling the reactor with the starting solution, the ratio of ammonia to metal was maintained at 1:1, and the pH was maintained at around 11.7 with the NaOH solution. Various reagents (MeSO 4 solution, NaOH solution, NH 3 solution) were simultaneously pumped into the reactor at different injection points. Typically, there should be more than 2 OH - ions for each metal ion in the solution. After 6 hours, 100 grams of seeds were added to the reactor from S1. The particle size span inside the reactor immediately increased and the D50 decreased. After at least 6 hours, the span steadily decreased to a value below 0.9. At this point, the particles had grown to around 6 μm to 11 μm. Here, the slurry in the overflow was collected in a 3 L beaker and the particles were allowed to settle in the beaker. The beaker was decanted every 30 minutes and the slurry was returned to the reactor. When the particles reached a sufficient size (around 11 μm), the addition of the reagents was stopped. c. Precipitation of S3 - shell: The metal sulfate solution (MeSO 4 ) introduced into the reactor in S2 was the second MeSO 4Switched to the solution. Resumed the addition of all chemicals and collected the overflow in a 3 L beaker. Decanted the beaker every 30 minutes to remove the filtrate and returned the slurry to the reactor. This procedure was used to continue this implementation until a shell with the desired thickness had grown. The precipitated metal (oxy)hydroxide was washed and filtered under a protective atmosphere to remove the dissolved salts and ammonia. The wet cake was dried under nitrogen in an oven at 150 °C. The final core-shell precipitated metal (oxy)hydroxide precursor had a Ni:Mn:Co core composition of 87:5:8 and a Ni:Mn:Co shell composition of 0:5:95. The average metal composition of the precursor determined by ICP analysis was Ni:Mn:Co = 85:5:10 (mol%). During the precipitation process, important factors such as pH, stirring speed, chemical concentration, and temperature were precisely controlled to maintain the composition of the final product constant. The shell thickness can be calculated based on the process conditions, but can also be measured post hoc using advanced analytical instruments such as XPS depth profiling or even TEM. 2. Mixing: The precursor prepared in step 1) was mixed with LiOH in an industrial blender at a Li to metal molar ratio (Li / Me) of 1.02 with respect to the total weight of the precursor. 3. Heating: The mixture obtained in step 2) was heated at 765 °C for 12 hours in an oxygen atmosphere, followed by grinding and sieving to obtain a heated powder with a composition of Ni:Mn:Co = 87:5:8 (mol%) determined by ICP analysis and a D50 of around 11.5 μm determined by PSD analysis. 4. Mixing: An aluminum sulfate solution prepared by dissolving 6300 ppm of Al 2 (SO 4 ) 3 powder in 3.5 wt% deionized water with respect to the weight of the heated powder was mixed with the heated powder. 5. Heating: The mixture obtained in step 4) was heated at 385 °C for 8 hours in an oxygen atmosphere, followed by grinding and sieving to obtain CEX1.1.

[0088] Comparative Example 1.2 (CEX1.2) CEX1.2 was prepared in the same manner as CEX1.1, except that in step 4, 4000 ppm of WO 3 was added together with 6300 ppm of Al 2 (SO 4 ) 3 .

[0089] Example 1.1 (EX1.1) EX1.1 was prepared in the same manner as CEX1.1, except that in step 2, 1000 ppm of Zr from ZrO 2 was added together with LiOH, and in step 4, 4000 ppm of W from WO 3 was added together with 6300 ppm of Al 2 (SO 4 ) 3 .

[0090] Example 1.2 (EX1.2) EX1.2 was prepared in the same manner as CEX1.1, except that in step 2, 2000 ppm of Zr from ZrO 2 was added together with LiOH, and in step 4, 4000 ppm of W from WO 3 was added together with 6300 ppm of Al 2 (SO 4 ) 3 .

[0091] Comparative Example 2 (CEX2) EX1.2 was prepared in the same manner as CEX1.1, except that in step 2, 3000 ppm of Zr from ZrO 2 was added together with LiOH, and in step 4, 4000 ppm of W from WO 3 was added together with 6300 ppm of Al 2 (SO 4 ) 3 .

[0092]

Table 3

[0093] * with respect to the molar contents of Ni, Mn, Co, S, W and Zr ** with respect to the molar contents of Ni, Mn, Co, S, W, Al and Zr *** The number of cycles at 80% capacity at 45 °C

[0094] The compositions of Ni, Mn, Co, Al, W, Zr and S, and the corresponding electrochemical properties, in Examples EX1.1 and EX1.2 according to the present invention, and Comparative Examples CEX1.1, CEX1.2 and CEX2, are summarized in Table 2. EX1.1 and EX1.2 can achieve the object of the present invention of providing a positive electrode active material having improved properties when used in a full cell, including minimizing the increase (i.e., swelling) in the thickness of the full cell and increasing the cycle life.

[0095] In EX1.1 and EX1.2, WO 3 and Al 2 (SO 4 ) 3 The step of mixing the compounds and the subsequent heat treatment step are each related to S B / S A > 1.0 and W B / W A > 1.0, where S B and W B are obtained by XPS measurement, and S A and W A are obtained by ICP measurement. That S B and W B are greater than 0 is related to the fact that in XPS measurement, the signal is obtained from the top of the sample, i.e., the first few nanometers (e.g., 1 nm to 10 nm) of the surface layer, indicating that these elements are present on the surface of the positive electrode active material. On the other hand, the ratios of S A and W A obtained from ICP measurement are from the whole particles. The ratios of XPS to ICP (S B / S A and W B / W A) being greater than 1 indicates that S and W mainly exist on the surface of the positive electrode active material.

Claims

1. A positive electrode active material powder for a lithium-ion rechargeable battery, wherein the positive electrode active material contains Li, M', and O, and M' is Ni having a content x of 60.0 mol% to 95.0 mol% with respect to M', Co having a content y of 0 ≤ y ≤ 39.98 mol% with respect to M', Mn having a content z of 0 ≤ z ≤ 39.98 mol% with respect to M', W having a content a of 0.01 mol% ≤ a ≤ 4.0 mol% with respect to M', Zr having a content b of 0.01 mol% to 0.20 mol% with respect to M', an element other than Li, O, Ni, Co, Mn, Al, W, S, and Zr having a content c of 0 ≤ c ≤ 2.0 mol% with respect to M', and S having a content d of 0.01 ≤ d ≤ 3.0 mol% with respect to M', Al having a content e of 0 ≤ e ≤ 2.0 mol% with respect to M' and x, y, z, a, b, c, d, and e are measured by ICP, x + y + z + a + b + c + d + e is 100.0 mol%, the positive electrode active material 【Number 1】 The content S of S defined as Ａ having wherein the positive electrode active material has a sulfur content S determined by XPS analysis Ｂ and S Ｂ is expressed as a molar fraction compared with the total molar fraction of Co, Mn, Ni, W, and S measured by XPS analysis Ratio S Ｂ / S Ａ > 1.0, the positive electrode active material 【Number 2】 has a content WA of W defined as the positive electrode active material has a content WB of W determined by XPS analysis, and WB is expressed as a molar fraction compared with the total molar fraction of Co, Mn, Ni, W, and S measured by XPS analysis, the ratio WB / WA > 1.0, positive electrode active material powder.

2. 0.01 mol% ≤ d ≤ 3.0 mol%, 【Number 3】 The content S of S defined as Ａ having The content of S determined by XPS analysis, S Ｂ has, and S Ｂ is expressed as a molar fraction compared with the total of the molar fractions of Co, Mn, Ni, W and S measured by XPS analysis, Ratio S Ｂ / S Ａ > 1.0 the positive electrode active material according to Claim 1.

3. With respect to M', x ≥ 65.0 mol%, x ≥ 70.0 mol%, x ≥ 75.0 mol%, or x ≥ 80.0 mol%, the positive electrode active material according to Claim 1.

4. Co in the content y is 1 mol% to 20 mol% with respect to M', the positive electrode active material according to Claim 1.

5. Mn in the content z is 1 mol% to 39.98 mol% with respect to M', the positive electrode active material according to Claim 1.

6. S in the content d is 0.10 mol% to 2.00 mol% with respect to M', the positive electrode active material according to Claim 1.

7. W in the content a is 0.10 mol% to 3.00 mol% with respect to M', the positive electrode active material according to Claim 1.

8. Zr in the content b is 0.10 mol% to 0.19 mol% with respect to M', the positive electrode active material according to Claim 1.

9. The cathode active material according to claim 1, wherein Al in the content e is 0.10 mol% to 1.00 mol% with respect to M'.

10. A process for the production of a cathode active material according to any one of claims 1 to 9, a step of preparing a lithium transition metal-based oxide compound, a step of mixing the lithium transition metal-based oxide compound with a sulfur source and water to obtain a mixture, and a step of obtaining the cathode active material by heating the mixture in a furnace at a temperature of 350°C to less than 500°C in an oxidizing atmosphere The process includes.

11. The process according to claim 10, wherein a tungsten source is added together with the sulfur source during the mixing step.

12. A battery comprising the cathode active material according to any one of claims 1 to 6.

13. Use of the battery according to claim 12 in an electric vehicle or in a hybrid electric vehicle.

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