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

Abstract

The present invention relates to a cathode active material for a rechargeable lithium-ion battery, wherein the cathode active material contains Li, M', and oxygen, 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', and D with a content a of 0 < a < 2.0 mol% with respect to M', where D contains elements other than Li, O, Ni, Co, Mn, F, W, and S, D, F with a content b > 0, preferably b is 0.1 mol% to 4.0 mol% with respect to M', W with a content c > 0, preferably 0.01 ≦ c ≦ 4.0 mol% with respect to M', S with a content d > 0, preferably 0.01 mol% to 3.0 mol% with respect to M', and B with a content e of 0 < e < 4.0 mol% with respect to M', x, y, z, a, c, and d are measured by inductively coupled plasma optical emission spectrometry (ICP-OES), b is measured by ion chromatography (IC), x + y + z + a + b + c + d = 100.0 mol%, and the cathode active material is defined as the F content F as in formula (I) A and the content W defined as in formula (II) A and the S content S defined as in formula (III) A and has, the cathode active material has an F content F B and a W content W B and an S content S B and has, F B , W B , and S B are determined by X-ray photoelectron spectroscopy (XPS) analysis, F B , W B , and S B are each represented as the molar fraction compared to the total molar fraction of Co, Mn, Ni, F, W, and S measured by XPS analysis, and the ratio F B / F A > 1.0, the ratio W B / W A > 1.0, and the ratio S B / S A > 1.0, to provide a cathode active material. JPEG2024520027000026.jpg39170

Description

Technical Field

[0001] The present invention relates to a lithium nickel-based oxide cathode active material for a lithium-ion secondary battery (LIB) suitable for use in electric vehicles (EVs) and hybrid electric vehicles (HEVs), which includes lithium transition metal oxide particles containing fluorine.

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 time.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, an object of the present invention is to provide a cathode active material having one or more improved characteristics such as a reduction in carbon content and an increase in initial discharge capacity (DQ1) in an electrochemical cell.

Means for Solving the Problems

[0004] Acknowledgment The present invention has been made with the support of the Materials / Parts Technology Development Program through the Korea Institute of Industrial Technology Evaluation with financial assistance from the Ministry of Trade, Industry and Energy (MOTIE, Republic of Korea). [Project Name: Development of 8C Rate Class High Output (High Discharge Rate) Lithium Ion Secondary Battery / Project Number: 20011287 / Contribution Rate: 100%]

[0005] This object is a cathode active material for a lithium-ion battery, the cathode active material containing Li, M', and oxygen, where M' is - Ni with a content x of 60.0 mol% to 95.0 mol%, preferably 80.0 mol% to 95.0 mol% with respect to M', and - Co with a content y of 0 ≦ y ≦ 40.0 mol% with respect to M', and Mn with a content z of 0≦z≦70.0 mol% relative to M', - D with a content a such that 0≦a≦2.0 mol % relative to M′, wherein D comprises elements other than Li, O, Ni, Co, Mn, F, W, B and S, preferably D comprises at least one element from the group consisting of Al, Ba, Ca, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, Zn and Zr, - F with a content b>0, preferably b=0.1 mol % to 4.0 mol % relative to M'; W with a content c>0 relative to M', preferably between 0.01 mol % and 4.0 mol %; - S with a content d of 0.01≦d≦3.0 mol% relative to M'; optionally B with a content e of 0≦e≦4.0 mol % relative to M′, where x, y, z, a, d and c are measured by ICP-OES, - b is measured by IC, - x+y+z+a+b+c+d is 100.0 mol%, The positive electrode active material is

[0006]

number

[0007] The F content, F, is defined as A and,

[0008]

number

[0009] The W content, W, is defined as A and,

[0010]

number

[0011] The S content, defined as S Ahaving the positive electrode active material has an F content F B and a W content W B and an S content S B having F B W B and S B which are determined by XPS analysis, where F B W B and S B are each expressed as the molar fraction compared to the sum of the molar fractions of Co, Mn, Ni, F, W, and S measured by XPS analysis. ratio F B / F A > 1.0, ratio W B / W A > 1.0, ratio S B / S A > 1.0.

[0012] In some cases, the positive electrode material contains B with a content e where e > 0, preferably 0.01 mol% ≤ e ≤ 4.0 mol%. The positive electrode active material

[0013]

Number

[0014] has a B content B defined as A having the positive electrode active material has a B content B determined by XPS analysis B having B B which is expressed as the molar fraction compared to the sum of the molar fractions of Co, Mn, Ni, F, W, S, and B measured by XPS analysis. ratio B B / B A > 1.0.

[0015] The present invention relates to the following embodiments.

[0016] Embodiment 1 In a first aspect, the present invention relates to a positive electrode active material for a lithium-ion battery, the positive electrode active material containing Li, M', and oxygen, 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', - D with a content a of 0 ≤ a ≤ 2.0 mol% with respect to M', where D contains elements other than Li, O, Ni, Co, Mn, F, W, B, and S, preferably D contains at least one element from the group consisting of Al, Ba, Ca, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, Zn, and Zr, D, - F with a content b of 0.1 mol% to 4.0 mol% with respect to M', - W with a content c of 0.01 mol% to 4.0 mol% with respect to M', - S with a content d of 0.01 ≤ d ≤ 3.0 mol% with respect to M', - Optionally, B with a content e of 0 ≤ e ≤ 4.0 mol% with respect to M', - x, y, z, a, c, d, and e are measured by ICP-OES, - b is measured by IC, - x + y + z + a + b + c + d + e is 100.0 mol%, The positive electrode active material is

[0017]

Number

[0018] The F content F defined as A and

[0019]

Number

[0020] The W content W defined as A and

[0021]

Number

[0022] S content S defined as A having The positive electrode active material has an F content F B a W content W B an S content S B having F B W B and S B are determined by XPS analysis. F B W B and S B are each expressed as the molar fraction compared to the total molar fractions of Co, Mn, Ni, F, W and S measured by XPS analysis. Ratio F B / F A > 1.0 Ratio W B / W A > 1.0 Ratio S B / S A > 1.0, regarding the positive electrode active material.

[0023] Preferably, F B / F A > 2.0, more preferably F B / F A > 5.0, most preferably F B / F A ≧ 30.0

[0024] Preferably, F B / F A < 70.0, more preferably F B / F A < 60.0, most preferably F B / F A ≦ 65.0

[0025] Preferably, S B / S A > 2.0, more preferably SB / S A >5.0, most preferably S B / S A ≧30.0.

[0026] Preferably, S B / S A <100.0, more preferably S B / S A <90.0, most preferably S B / S A ≦95.0.

[0027] Preferably, W B / W A >2.0, more preferably W B / W A >5.0, most preferably W B / W A ≧60.0.

[0028] Preferably, W B / W A <130.0, more preferably W B / W A ≦110.0.

[0029] Preferably, the Ni content is x≧65.0 mol% with respect to M’, more preferably x≧70.0 mol%, even more preferably more than 75 mol%.

[0030] Preferably, the Ni content is x≦93.0 mol% with respect to M’, more preferably x≦91.0 mol%, even more preferably less than 87 mol%.

[0031] Preferably, the Co content is y>2.0 mol% with respect to M’, more preferably y≧3.0 mol%, even more preferably y≧4.0 mol%.

[0032] In one embodiment, the Co content is y<20 mol% with respect to M’, more preferably y<15 mol%, even more preferably y<12.5 mol%.

[0033] Preferably, the Mn content is z > 1 mol% with respect to M', more preferably ≧ 3.0 mol%, and even more preferably z ≧ 4.0 mol%.

[0034] In one embodiment, the Mn content is y < 20 mol% with respect to M', more preferably Mn < 15 mol%, and even more preferably < 12.5 mol%.

[0035] Preferably, a is 0.01 mol% to 2.0 mol% with respect to M', and preferably, a is 0.1 mol% to 1.8 mol%.

[0036] Preferably, S is present in a content b of 0.1 mol% to 2 mol%, and even more preferably 0.2 mol% to 1 mol%.

[0037] Preferably, F is present in a content b of 0.1 mol% to 2 mol%, and even more preferably 0.2 mol% to 1 mol%.

[0038] Preferably, W is present in a content b of 0.1 mol% to 2 mol%, and even more preferably 0.2 mol% to 1 mol%.

[0039] In some cases, the positive electrode active material further contains B in a content of 0 to 4.0 mol% with respect to M', preferably 0.1 mol% to 2 mol%, and even more preferably 0.2 mol% to 1 mol%.

[0040] Preferably, the positive electrode active material is in the form of a powder.

[0041] For the sake of completeness, it should be noted that in the definitions of the present invention, when the content of an element is described using the symbol "0 ≦", this means that the presence of the element is optional.

[0042] Embodiment 2 In a second aspect, the present invention provides a battery including the positive electrode active material of the present invention.

[0043] Embodiment 3 In a third aspect, the present invention provides for the use of a battery according to the present invention in a portable computer, a tablet, a mobile phone, an electric vehicle, or an energy storage system.

[0044] Embodiment 4: A positive electrode active material for a lithium ion battery according to a fourth embodiment, wherein the positive electrode active material contains Li, M', and oxygen, and 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', - D with a content a of 0 ≦ a ≦ 2.0 mol% with respect to M', where D contains at least one element from the group consisting of Al, Ba, Ca, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, Zn, and Zr, - F with a content b of 0.1 mol% to 4.0 mol% with respect to M', - W with a content c of 0.1 mol% to 4.0 mol% with respect to M', - S with a content d of 0 ≦ d ≦ 3.0 mol% with respect to M', - B with a content e of 0 ≦ e ≦ 4.0 mol% with respect to M', and - x, y, z, a, d, e, and c are measured by ICP - OES, - b is measured by IC, - x + y + z + a + b + c + d + e is 100.0 mol%,

[0045]

Number

[0046] The positive electrode active material has an F content F defined as A and

[0047]

Number

[0048] The W content W defined as A and having The positive electrode active material has an F content F B and a W content W B and having F B and W B are determined by XPS analysis, and F B and W B are each expressed as a molar fraction compared to the sum of the molar fractions of Co, Mn, Ni, F, W, B, and S measured by XPS analysis. Ratio F B / F A > 1.0, Ratio W B / W A > 1.0. Preferably, F B / F A > 2.0. Preferably, W B / W A > 1.0.

[0049] For the sake of completeness, it should be noted that in the definition of the present invention, when the content of an element is described using the symbol "0≦", this means that the presence of the element is optional.

[0050] Embodiment 5 In the fifth embodiment, preferably according to Embodiment 4, the substance contains S with a content d of 0.01 mol% ≦ d ≦ 3.0 mol%, and the positive electrode active material has

[0051]

Number

[0052] The S content S defined as A having The positive electrode active material has an S content S determined by XPS analysis B having S BIt is represented as a molar fraction compared with the total molar fractions of Co, Mn, Ni, F, W, S, and B measured by XPS analysis, Ratio S B / S A > 1.0. Preferably, S B / S A > 2.0.

[0053] Embodiment 6 In the sixth embodiment, preferably according to Embodiment 4 or 5, the substance contains B with a content e of 0.01 mol% ≤ e ≤ 4.0 mol%, and the positive electrode active material

[0054]

Number

[0055] B content B defined as A having, the positive electrode active material has a B content B determined by XPS analysis B having, and B B is represented as a molar fraction compared with the total molar fractions of Co, Mn, Ni, F, W, S, and B measured by XPS analysis, Ratio B B / B A > 1.0. Preferably, B B / B A > 2.0.

[0056] Embodiment 7 In the seventh embodiment, the present invention is a positive electrode active material containing Li, M' and oxygen, 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', - D with a content a of 0 ≤ a ≤ 2.0 mol% with respect to M’, where D contains at least one element from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, Zn, and Zr, D and, - F with a content b of 0.1 mol% to 4.0 mol% with respect to M’, - W with a content c of 0.0 mol% to 4.0 mol% with respect to M’, - S with a content d of 0.01 mol% to 3.0 mol% with respect to M’, - B with a content e of 0 ≤ e ≤ 4.0 mol%, and - x, y, z, a, c, d, and e are measured by ICP - OES, - b is measured by IC, - x + y + z + a + b + c + d + e is 100.0 mol%,

[0057]

Number

[0058] The positive electrode active material has an F content F defined as A and,

[0059]

Number

[0060] an S content S defined as A and, and has The positive electrode active material has an F content F B and F B is determined by XPS analysis, and F B and S B are each expressed as the molar fraction compared to the total molar fraction of Co, Mn, Ni, F, W, B, and S measured by XPS analysis, and the ratio F B / F A > 1.0, The ratio S B / S A > 1.0, regarding the positive electrode active material. Preferably, F B / F A > 2.0. Preferably, S B / S A > 2.0.

Mode for Carrying Out the Invention

[0061] The positive electrode active material according to the present invention typically has one or more of the following advantages: reduction in carbon content and increase in cycle life. This is considered to be achieved by a positive electrode material containing fluorine, sulfur, and tungsten.

[0062] Typically, the positive electrode material of the present invention contains secondary particles having a median diameter D50 of at least 2 μm, preferably at least 3 μm, as determined by laser diffraction particle size analysis.

[0063] Preferably, the material has a secondary particle median diameter D50 of at most 16 μm, preferably at most 15 μm, as determined by laser diffraction particle size analysis.

[0064] It is obvious that further product embodiments according to the present invention can be provided by combining the features covered by the various product embodiments described above.

[0065] In a further aspect of the present invention, the positive electrode material of the present invention is as follows: Step 1) A step of mixing a lithium transition metal oxide with an F-containing compound and a W-containing compound to obtain a first mixture; Step 2) A step of mixing a dry powder with a solution containing an S-containing compound to obtain a mixture; Step 3) A step of heating the mixture in an oxidizing atmosphere at a temperature of 250 °C or higher and lower than 500 °C to obtain a positive electrode active material. It may be produced by a method including these steps.

[0066] Preferably, the F-containing compound used in Step 1) is PVDF.

[0067] Preferably, the amount of the F used in step 1) is 300 ppm to 3000 ppm based on the weight of the lithium transition metal oxide. More preferably, the amount of the F used in step 1) is 500 ppm to 2000 ppm.

[0068] Preferably, in step 1), the W-containing compound is added together with the F-containing compound in an amount of 2000 ppm to 9000 ppm of W based on the weight of the lithium transition metal oxide.

[0069] Preferably, the W-containing compound used in step 1) is WO3.

[0070] Preferably, the amount of the W used in step 1) is 3000 ppm to 8000 ppm.

[0071] Preferably, the solution used in step 2) contains S in an amount of 500 ppm to 5000 ppm based on the weight of the lithium transition metal oxide. More preferably, the solution used in step 2) contains S in an amount of 700 ppm to 3000 ppm based on the weight of the dry powder.

[0072] Preferably, the S-containing compound used in step 2) is Al2(SO4)3.

[0073] Optionally, an element-containing compound other than Li, O, Ni, Co, Mn, F, W, and S can be added to the cathode material. Preferably, the element contains at least one of the elements from the group consisting of Al, Ba, Ca, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, Zn, and Zr. Preferably, the element-containing compound is added in the mixing step together with the lithium source when preparing the transition metal oxide. Alternatively, the element-containing compound may be added in the preparation of the precursor.

[0074] In the framework of the present invention, ppm means parts per million for the unit of concentration and represents 1 ppm = 0.0001 wt%.

[0075] In the following detailed description, preferred embodiments are described in order to implement 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 will be apparent from the following detailed description and consideration of the accompanying drawings.

[0076] A) ICP-OES analysis The Li, Ni, Mn, Co, Al, and S, and optionally B content of the positive electrode active material powder is measured by the Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) method using an Agillent ICP 720-OES. In an Erlenmeyer flask, dissolve 2 grams of the product powder sample in 10 mL of high-purity hydrochloric acid. Cover the flask with glass and heat it on a hot plate at 380 °C until the precursor is completely dissolved. After cooling to room temperature, pour the solution in the Erlenmeyer flask into a 250 mL volumetric flask. Then, fill the volumetric flask with deionized water up to the 250 mL mark and subsequently homogenize it completely. Take an appropriate amount of the solution with a pipette, transfer it to a 250 mL volumetric flask for the second dilution, and fill the volumetric flask with an internal standard substance and 10% hydrochloric acid up to the 250 mL mark and then homogenize it. Finally, use this 50 mL solution for ICP-OES measurement.

[0077] B) PSD 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 powder sample in an aqueous medium. To improve the dispersion of the powder, apply sufficient ultrasonic irradiation and stirring and introduce an appropriate surfactant. D50 is defined as the particle size at 50% of the cumulative volume % distribution obtained from the Malvern Mastersizer 3000 based on the Hydro MV measurement value.

[0078] C) Ion Chromatography (IC) Analysis The amount of F in the positive electrode active material powder is measured by using the ion chromatography (IC) method with Dionex ICS-2100 (Thermo scientific). Before use, a 250 mL volumetric flask and a 100 mL volumetric flask are rinsed with a mixed solution of 65 wt% HNO3 and deionized water in a volume ratio of 1:1, and then the flasks are rinsed with deionized water at least 5 times. 2 mL of HNO3, 2 mL of H2O2, and 2 mL of deionized water are mixed as solvents. 0.5 gram of the powder sample is dissolved in the mixed solvent. The solution is completely transferred from the container to a 250 mL volumetric flask, and the 250 mL volumetric flask is filled with deionized water up to the 250 mL mark. The filled flask is shaken well to ensure the homogeneity of the solution. 9 mL of the solution is transferred from the 250 mL flask to a 100 mL volumetric flask. The 100 mL volumetric flask is filled with deionized water up to the 100 mL mark, and the diluted solution is shaken well to obtain a uniform sample solution. 2 mL of the sample solution is inserted into a 5 mL IC vial through a syringe-OnGuard cartridge for IC measurement.

[0079] D) Coin Cell Test D1) Fabrication of Coin Cell Regarding the fabrication of the positive electrode, a slurry containing a positive electrode active material powder, a conductor (Super P, Timcal), and a binder (KF#9305, Kureha) in a weight ratio of 96.5:1.5:2.0 in a solvent (NMP, Mitsubishi) is prepared using a high-speed homogenizer. 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 calendaring 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.

[0080] D2) 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 2. Each cell is cycle-tested at 25 °C using a Toscat-3100 computer-controlled galvanostatic cycling station (manufactured by Toyo). 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.

[0081]

Equation

[0082] 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.

[0083]

Table 1

[0084] E) 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 the elements measured by XPS are contained in the surface layer.

[0085] 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).

[0086] Monochromatic Al Kα radiation (hv = 1486.6 eV) is used at a spot size of 400 μm and a measurement angle of 45°. A wide survey scan for identifying the elements present on the surface is performed at a pass energy of 200 eV. The Cls peak having the maximum intensity (or center) at a binding energy of 284.8 eV is used as the calibration peak position after data collection.

[0087] Thereafter, for each identified element, an accurate narrow scan is scanned at least 10 times at 50 eV to determine the accurate surface composition.

[0088] 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 follow Table 2a. The line shape GL(30) is the Gaussian / Lorentz product formula for a 70% Gaussian line and a 30% Lorentz line.

[0089] LA(α, β, m) is an asymmetric linear shape, where α and β define the tail spread of the peak, and m defines the width.

[0090]

Table 2

[0091] For Co, W, S, or B peaks, restrictions regarding the peaks defined according to Table 2b are set. W5p3 is not quantified.

[0092]

Table 3

[0093] The surface contents of F, W, S, and B are expressed as the mole fraction of F, W, S, and B on the surface of the particles divided by the total content of Ni, Mn, Co, W, B, and S on the surface when determined by XPS. They are calculated as follows.

[0094]

Equation

[0095] F) Carbon analyzer The carbon content of the positive electrode active material powder is measured by an Emia-Expert carbon / sulfur analyzer manufactured by Horiba, Ltd. 1 g of the positive electrode active material powder is placed in a ceramic crucible in a high-frequency induction furnace. 1.5 g of tungsten and 0.3 g of tin as accelerators are added into the crucible. The powder is heated at a programmable temperature, and then the gas generated during combustion is analyzed by an infrared detector. The carbon concentration is determined by the analysis of CO2 and CO.

[0096] The present invention will be further described by the following (non-limiting) examples.

[0097] Comparative Example 1.1 CEX1.1 was obtained by a solid-state reaction between a lithium source and a transition metal-based source precursor, which was carried out as follows. 1) Coprecipitation: A transition metal-based oxyhydroxide precursor having a metal composition of Ni 0.80 Mn 0.10 Co 0.10 was prepared by a coprecipitation process in which nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia mixed in a large continuous stirred tank reactor (CSTR). 2) Blend: The precursor prepared in step 1) and LiOH as a lithium source were homogeneously blended at a lithium-to-metal M' (Li / M') ratio of 1.00 in an industrial blending apparatus. 3) First heating: The blend from step 2) was sintered at 805 °C for 12 hours in an oxygen atmosphere. The product was pulverized, classified, and sieved to obtain a first heating powder. 4) Wet mixing: The first heating powder from step 3) was mixed with an aluminum sulfate solution prepared by dissolving about 3800 ppm of Al2(SO4)3 powder in 3.5 wt% deionized water based on the weight of the first heating powder. 5) Second heating: The mixture obtained from step 4) was heated at 385 °C for 8 hours in an oxygen atmosphere, followed by pulverization and sieving. The obtained CEX1.1 had a D50 of about 13 μm as determined by the above PSD method B.

[0098] Comparative Example 1.2 CEX1.2 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step in step 4). In the dry mixing step, 4000 ppm of W from WO3 powder was mixed with the first heating powder. CEX1.2 had a D50 of 13 μm as determined by the above PSD method B.

[0099] Example 1.1 EX1.1 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4). In the dry mixing step, 650 ppm of F from PVDF powder and 4000 ppm of W from WO3 powder were mixed with the first heated powder. EX1.1 had a D50 of 13 μm as determined by the above PSD method B.

[0100] Example 1.2 EX1.2 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4). In the dry mixing step, 650 ppm of F from PVDF powder and 6000 ppm of W from WO3 powder were mixed with the first heated powder. EX1.2 had a D50 of 13 μm as determined by the above PSD method B.

[0101] Example 1.3 EX1.3 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4). In the dry mixing step, 980 ppm of F from PVDF powder and 4000 ppm of W from WO3 powder were mixed with the first heated powder. EX1.3 had a D50 of 13 μm as determined by the above PSD method B.

[0102] Example 1.4 EX1.4 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4). In the dry mixing step, 650 ppm of F from PVDF powder and 3000 ppm of W from WO3 powder were mixed with the first heated powder. EX1.4 had a D50 of 13 μm as determined by the above PSD method B.

[0103] Example 1.5 EX1.5 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4). In the dry mixing step, 1300 ppm of F from PVDF powder and 4000 ppm of W from WO3 powder were mixed with the first heated powder. EX1.5 had a D50 of 13 μm as determined by the above PSD method B.

[0104] Example 1.6 EX1.6 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4) and 6350 ppm of Al2(SO4)3 was mixed in the wet mixing step of step 4). In the dry mixing step, 650 ppm of F from PVDF powder and 4000 ppm of W from WO3 powder were mixed with the first heated powder. EX1.6 had a D50 of 13 μm as determined by the above PSD method B.

[0105] Comparative Example 2.1 CEX2.1 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4). In the dry mixing step, 650 ppm of F from PVDF powder was mixed with the first heated powder. CEX2.1 had a D50 of 13 μm as determined by the above PSD method B.

[0106] Comparative Example 2.2 CEX2.2 was prepared in the same manner as CEX1.1, except that a dry mixing step was added before the wet mixing step of step 4) and 6350 ppm of Al2(SO4)3 was mixed in the wet mixing step of step 4). In the dry mixing step, 650 ppm of F from PVDF powder was mixed with the first heated powder. CEX2.2 had a D50 of 13 μm as determined by the above PSD method B.

[0107] The use of PVDF, WO3 and Al2(SO4)3 compounds in the preparation of EX1.1, EX1.2, EX1.3, EX1.4, EX1.5, and EX1.6 was F B / F A > 1.0, WB / W A >1.0, and S B / S A results in >1.0, and F B , W B , and S B are obtained by XPS measurement, and F A , W A , and S A are obtained by ICP-OES measurement.

[0108]

Table 4

[0109] F greater than 0 B , S B , and W B are related to XPS measurement where the signal is acquired from the top of the sample, i.e., the first few nanometers (e.g., 1 nm to 10 nm) of the surface layer, indicating the presence of the element on the surface of the cathode active material. On the other hand, the atomic ratios of F A , S A , and W A obtained from ICP-OES measurement are from the whole particles. The fact that the ratio of XPS to ICP-OES of F B / F a , S B / S A , and W B / W A is greater than 1 indicates that the F, S, and W elements mainly exist on the surface of the cathode active material.

[0110] Table 3 above shows that when the cathode active materials EX1.1 to EX1.6 containing S, F, and W according to the present invention are used in an electrochemical cell, they have the characteristics of reduced carbon content and increased DQ1, which are improved compared to Comparative Examples CEX1.1, CEX1.2, CEX2.1, and CEX2.2.

[0111] Comparative Example 3 CEX3 was obtained by a solid-state reaction between a lithium source and a transition metal-based source precursor performed as follows. 1) Coprecipitation: A transition iron-based oxyhydroxide precursor having a concentration gradient known as a two-step full concentration gradient (TSFCG) precursor was prepared according to J. Mater. Chem. A, 2015, 3, 22183. The total metal composition was Ni 0.85 Mn 0.10 Co 0.05 . 2) Blend: 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 1.005. 3) First heating: The blend from step 2) was sintered at 765 °C for 10 hours in an oxygen atmosphere. The product was pulverized, classified, and sieved to obtain CEX3 having a D50 of 10.5 μm.

[0112] Example 3.1 EX3.1 was prepared by mixing CEX3 with PVDF powder and WO3 powder and then heating at 385 °C. EX3.1 contains 1300 ppm of F and 4500 ppm of W.

[0113] Example 3.2 EX3.2 was prepared by mixing CEX3 with H3BO3, PVDF powder, and WO3 powder and then heating at 385 °C. EX4.2 contains 500 ppm of B, 1300 ppm of F, and 4500 ppm of W.

[0114] The steps of mixing PVDF, WO3 and H3BO3 compounds followed by heat treatment in EX3.1 and EX3.2 each result in F B / F A > 1.0, W B / W A > 1.0, and B B / B A > 1.0, where F B , W B , and B B are obtained by XPS measurement, and F A , W A , and B A are obtained by ICP-OES measurement.

[0115]

Table 5

[0116] F greater than 0 B , S B , B b , and W B are related to XPS measurements where 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 the presence of the element on the surface of the cathode active material. On the other hand, the atomic ratios of F A , S A , B a , and W A are from the whole particles. The fact that the ratio of XPS to ICP-OES of F B / F a , S B / S A , B B / B A , and W B / W A is greater than 1 indicates that the F, S, B, and W elements are mainly present on the surface of the cathode active material

Claims

1. A method for producing a cathode active material for a rechargeable lithium ion battery, comprising: the following consecutive steps: Step 1) mixing a lithium transition metal oxide with an F-containing compound and a W-containing compound to obtain a first mixture; Step 2) mixing a dry powder with a solution containing an S-containing compound to obtain a mixture; Step 3) heating the mixture in an oxidizing atmosphere at a temperature of 250 °C or higher and lower than 500 °C to obtain the cathode active material. The cathode active material contains Li, M', and oxygen, and 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'; - D with a content a of 0 ≤ a ≤ 2.0 mol% with respect to M', where D contains elements other than Li, O, Ni, Co, Mn, F, W, and S; - F with a content b > 0 with respect to M'; - W with a content c > 0 with respect to M'; - S with a content d > 0 with respect to M'; - B with a content e of 0 ≤ e ≤ 4.0 mol% with respect to M'; and x, y, z, a, c, d, and e are measured by inductively coupled plasma optical emission spectrometry (ICP-OES), - b is measured by ion chromatography (IC), - x + y + z + a + b + c + d + e = 100.0 mol%. The cathode active material is 【Number 1】 The F content F defined as Ａ and 【Number 2】 The W content W defined as Ａ and 【Number 3】 The S content S defined as Ａ and having wherein the positive electrode active material has an F content F Ｂ and a W content W Ｂ and an S content S Ｂ and F Ｂ , W Ｂ , and S Ｂ are determined by XPS analysis, and F Ｂ , W Ｂ , and S Ｂ are each represented as a molar fraction compared to the total of the molar fractions of Co, Mn, Ni, F, W, and S measured by XPS analysis Ratio F Ｂ / F Ａ > 1.0, Ratio W Ｂ / W Ａ > 1.0, Ratio S Ｂ / S Ａ > 1.0, method.

2. The cathode active material contains B with a content e > 0, and the cathode active material is 【Number 4】 The B content B defined as Ａ having wherein the positive electrode active material has a B content B determined by XPS analysis Ｂ and B Ｂ is expressed as a molar fraction compared with the total molar fractions of Co, Mn, Ni, F, W, S, and B measured by XPS analysis Ratio B Ｂ / B Ａ The method according to claim 1, wherein it is > 1.

0.

3. Ratio F Ｂ / F Ａ The method according to claim 1, wherein > 2.

0.

4. Ratio W Ｂ / W Ａ The method according to claim 1, wherein > 2.

0.

5. Ratio S Ｂ / S Ａ The method according to claim 1, wherein the ratio is > 2.

0.

6. Ratio B Ｂ / B Ａ The method according to claim 1, wherein it is > 2.

0.

7. The method according to claim 1, wherein D contains at least one element selected from the group consisting of Al, Ba, Ca, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, Y, V, Zn, and Zr.

8. The method according to claim 1, wherein D has a content a of 0.01 mol% to 2.0 mol% with respect to M.

9. The method according to claim 1, wherein the F-containing compound used in Step 1 is PVDF.

10. The S-containing compound used in step 2) is Al ２ (SO ４ ) ３ The method according to claim 1, wherein the method is as described above.

11. The W-containing compound is WO ３ The method according to claim 1, wherein the method is as described above.

12. The method according to claim 1, wherein a B-containing compound is added together with the F-containing compound and the W-containing compound in Step 1.

13. wherein the B-containing compound is H ３ BO ３ The method according to claim 12, wherein the method is as described above.

Images