Positive electrode active material for rechargeable lithium-ion batteries

Abstract

1. A cathode active material for a rechargeable lithium ion battery, the cathode active material comprising Li, Co, O, and optionally M', where M' comprises Al and / or Ti, and optionally one or more elements selected from Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr, a molar ratio of Co to M'+Co (Co / (M'+Co)) is greater than 0.90 as determined by ICP-OES analysis, the cathode active material comprising a first LCO powder and a second LCO powder, both of which are single crystal powders, the first LCO powder having a first median diameter D50A of 12 μm to 25 μm as determined by laser diffraction particle size analysis, the second LCO powder having a second median diameter D50B of 3 μm to 8 μm as determined by laser diffraction particle size analysis, and a volume fraction of the second LCO powder relative to a total volume of the cathode active material is 10% to 40%, as determined by laser diffraction particle size analysis.

Description

[Technical field]

[0001] The present invention relates to a lithium cobalt-based metal oxide (LCO) cathode active material for rechargeable lithium-ion batteries. More specifically, the present invention relates to a particulate LCO cathode active material comprising a first LCO powder and a second LCO powder. [Background technology]

[0002] The present invention relates to a single crystal active cathode material powder for a rechargeable lithium-ion battery (LIB), comprising a first LCO powder and a second LCO powder, the first LCO powder having a higher median diameter D50 than the second LCO powder, where the first LCO powder is single crystal.

[0003] Such cathode active materials comprising a first LCO powder and a second LCO powder, the first LCO powder having a higher median diameter D50 than the second LCO powder, are already known, for example in International Publication WO 2012 / 171780 A1 (hereinafter referred to as WO'780). WO'780 discloses an cathode active material powder comprising a mixture of a large monocrystalline LCO powder and a small polycrystalline LCO powder. However, the cathode active material of WO'780 has been shown to have poor high temperature and high voltage stability when used in an electrochemical cell, as measured by coin cell float tests. Furthermore, the powder density is low, resulting in a lower electrode density.

[0004] Therefore, the objective of the present invention is to provide a low Q float (QF) and low Co dissolution (CO) determined by coin cell float testing. Dis The present invention provides a cathode active material that is stable in electrochemical cell use at high temperatures and voltages, as indicated by a low thickness increase after 4 hours (T4h) as determined by a full cell bulge test, and a low powder density as measured by pressed density. Summary of the Invention [Means for solving the problem]

[0005] The object of the present invention is achieved by providing an active cathode material for a rechargeable lithium-ion battery according to claim 1. It is indeed observed that better stability and high packed density can be obtained using the active cathode material of the present invention, as illustrated by the examples and supported by the results shown in Tables 1 and 2. Example 1 teaches an active cathode material comprising a first LCO powder and a second LCO powder, where the first single crystal LCO powder has a higher median diameter D50 than the second single crystal LCO powder.

[0006] For further guidance, figures are included to better understand the teachings of the present invention, which are intended to aid in the explanation of the invention and are not intended to limit the invention of this disclosure. [Brief description of the drawings]

[0007] [Figure 1a] 1a to 1c show scanning electron microscope (SEM) images of the positive electrode active material powders EX1, CEX1, and CEX2, respectively. [Figure 1b] 1a to 1c show scanning electron microscope (SEM) images of the positive electrode active material powders EX1, CEX1, and CEX2, respectively. [Figure 1c] 1a to 1c show scanning electron microscope (SEM) images of the positive electrode active material powders EX1, CEX1, and CEX2, respectively. [Figure 1d] Calculation of the primary particle size of the 2nd LCO from the SEM image of EX1 is shown. [Diagram 2] SEM and EDS mapping of Co, Al, Ti, and Mg elements on EX1 particles are shown. Ti- and Mg-rich islands are seen on the cathode active material particles. [Diagram 3] 1 shows a particle size distribution graph of EX1 deconvoluted into two peaks corresponding to the first and second LCO powders, where the x-axis is particle size in logarithmic scale and the y-axis is volume fraction. [Figure 4] 1 shows a graph of swelling tested on a full cell, where the x-axis is time in hours and the y-axis is the increase in cell thickness in percent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs.

[0009] positive electrode active material In a first aspect, the present invention provides an active cathode material for a rechargeable lithium-ion battery, the active cathode material comprising Li (lithium), Co (cobalt), O (oxygen), and optionally M', where M' comprises Al and / or Ti, and optionally one or more elements selected from Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr, and a molar ratio of Co to M'+Co (Co / (M'+Co)) is greater than 0.90 and less than or equal to 1.00, preferably less than 1.00, more preferably less than or equal to 0.99, as determined by ICP-OES analysis; the positive electrode active material includes a first LCO powder and a second LCO powder, both of which are single crystal powders; The first LCO powder has a median diameter D50 of 12 μm to 25 μm as determined by laser diffraction particle size distribution analysis. A having The second LCO powder has a median diameter D50 of 3 μm to 8 μm, as determined by laser diffraction particle size distribution analysis. B having The volume fraction of the second LCO powder relative to the total volume of the positive electrode active material is 10%-40%, as determined by laser diffraction particle size analysis.

[0010] The concept of single crystal powder is well known in the art of cathode active materials. It relates to powders having predominantly single crystal particles. Such powders are a separate type of powder compared to polycrystalline powders made from particles that are predominantly polycrystalline. Those skilled in the art can easily distinguish between these two classes of powders based on microscopic images.

[0011] Single crystal particles are also known in the art as monolithic particles, integral particles, or / and monocrystalline particles.

[0012] A technical definition of a single crystal powder is not necessary since such powders can be readily recognized by one skilled in the art using an SEM, however, in the context of the present invention, a single crystal powder may be considered to be defined as a powder in which 80% or more of the particles by number are single crystal particles. This means a powder having a size of at least 45 μm by at least 60 μm (i.e., at least 2700 μm 2 ), preferably at least 100 μm×100 μm (i.e., at least 10,000 μm 2 ) on an SEM image with a field of view.

[0013] A single crystal particle is a particle that is an individual crystal or is formed from fewer than five, preferably a maximum of three, primary particles that are themselves individual crystals. This can be observed by observing the grain boundaries with a suitable microscopic technique such as a Scanning Electron Microscope (SEM).

[0014] In determining whether a particle is a single crystal particle, grains having a maximum linear dimension observed by SEM that is smaller than 20% of the median diameter D50 of the powder as determined by laser diffraction are ignored. This avoids inadvertently considering particles that are essentially single crystal but have some very small other grains, e.g., polycrystalline coatings deposited on them, as not being single crystal particles.

[0015] Preferably, the positive electrode active material contains M'.

[0016] Preferably, M' includes Al and Ti.

[0017] Preferably, the present invention provides a cathode active material according to the first aspect of the invention, wherein the median diameter D50 of the volume ratio of the second LCO powder to the total volume of the cathode active material is 10.0 volume % to 35.0 volume %, preferably the volume ratio is 15.0 volume % to 30.0 volume %, more preferably the volume ratio is equal to 15.0, 20.0, 25.0, 30.0, or any value therebetween.

[0018] In a preferred embodiment, the cathode active material of the first aspect of the present invention has a molecular weight of 0.10 m as measured by the BET method. 2 / g~0.25m 2 Preferably, the positive electrode active material has a specific surface area (SA) of at least 0.11 m 2 / g, at least 0.12m 2 / g, at least 0.13m 2 / g, or even at least 0.14 m 2 / g, or in particular at least 0.15 m 2 Preferably, the positive electrode active material has an SA of at most 0.25 m 2 / g, maximum 0.24m 2 / g, maximum 0.22m 2 / g, maximum 0.20m 2 / g.

[0019] In a preferred embodiment, the cathode active material of the first aspect of the present invention has a compressibility of 3.9 g / cm, determined after application of a uniaxial pressure of 207 MPa for 30 seconds. 3 ~4.3g / cm 3 Preferably, the positive electrode active material has a compressed density (PD) of at least 3.92 g / cm 3 , at least 3.93 g / cm 3 , at least 3.94 g / cm 3 , or even at least 3.95 g / cm 3 , or in particular at least 3.97 g / cm 3 Preferably, the positive electrode active material has a PD of at most 4.30 g / cm 3 , up to 4.20g / cm 3 , up to 4.15g / cm 3, up to 4.10g / cm 3 He has PD.

[0020] In a preferred embodiment, the cathode active material of the first aspect of the present invention has a pressed density to specific surface area (PD / SA) ratio of 19 to 28. Preferably, the cathode active material has a PD / SA ratio of at least 20.0, at least 20.5, at least 21.0, or even at least 21.5, or especially at least 22.0. Preferably, the cathode active material has a PD / SA ratio of at most 27.0, at most 26.0, at most 25.0, or at most 24.5.

[0021] In a preferred embodiment, the cathode active material comprises particles having Ti and Mg rich islands on the surface of the particles as determined by SEM-EDS elemental mapping. Preferably, the Ti and Mg rich islands have a diameter of 0.2 μm to 3.0 μm as determined by SEM-EDS elemental mapping analysis.

[0022] Preferably, the present invention provides an active cathode material according to the first aspect of the present invention, the active cathode material comprising Li, Co, M', and oxygen, where M' comprises Al, Ti, and optionally one or more elements selected from Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr.

[0023] First LCO powder The present invention relates to a first LCO powder having a median diameter D50 of 12 μm to 25 μm as determined by laser diffraction particle size analysis. A More preferably, the single crystal powder has a median diameter D50 A is equal to 13, 15, 17, 19, 21, 23, 25 μm, or any value therebetween.

[0024] Preferably, the present invention relates to a method for producing a first LCO powder comprising the steps of: A ', where the metal M A' comprises Al, Ti, and optionally one or more elements selected from Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr; M A ' + Molar ratio of Co to CO (CO / (M A The positive electrode active material according to the first aspect of the present invention is provided, wherein the .DELTA..times ...

[0025] 2nd LCO powder Preferably, the present invention relates to a second LCO powder having a median diameter D50 of 3 μm to 8 μm as determined by laser diffraction particle size analysis. B More preferably, the single crystal powder has a median diameter D50 B is equal to 3, 4, 5, 6, 7, 8 μm, or any value therebetween.

[0026] Preferably, the second LCO powder comprises a powder having an average primary particle size of between 3 μm and 7 μm, more preferably the average primary particle size is equal to 3, 4, 5, 6, 7, or any value therebetween, as determined by SEM analysis.

[0027] Preferably, the present invention relates to a first LCO powder that is free of Li, Co, oxygen, and optionally a metal M. A ', where the metal M A ' contains Al, Ti, and optionally one or more elements selected from Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr, and the molar ratio of Co to MA'+CO (CO / (M A The positive electrode active material according to the first aspect of the present invention has a composition of more than 0.90 and not more than 1.00, preferably less than 1.00, more preferably not more than 0.99. The composition can be determined by known analytical methods such as ICP-OES (inductively coupled plasma optical emission spectroscopy).

[0028] Method for producing cathode active material In a second aspect, the present invention provides a method for producing a positive electrode active material, comprising: Step 1) Median diameter D50 of 12 μm to 25 μm A A first lithium cobalt-based metal oxide powder having a median diameter D50 of 3 μm to 8 μm. B a step of mixing a second lithium cobalt-based metal oxide powder having the formula: with TiO2 to obtain a mixture, wherein the first lithium cobalt-based metal oxide powder and the second lithium cobalt-based metal oxide powder are both single crystal powders, and the weight fraction of the second lithium cobalt-based metal oxide relative to the total weight of the positive electrode active material is 10% to 40%, preferably 10% by weight to 35% by weight, and more preferably 15% by weight to 30% by weight; Step 2) heating the mixture for 5 to 20 hours at a temperature of 700°C to 1100°C. Preferably, the heating temperature is 800°C to 1050°C.

[0029] Batteries containing cathode active materials and uses thereof In a third aspect, the present invention provides a battery cell comprising an active cathode material according to the first aspect of the present invention.

[0030] In a fourth aspect, the present invention provides the use of an active cathode material according to the first aspect of the present invention in a battery of any one of a portable computer, a tablet, a mobile phone, an electric vehicle, and an energy storage system. EXAMPLES

[0031] The following examples are intended to further clarify the invention, but are not intended to limit the scope of the invention.

[0032] 1. Description of analysis method 1.1. Inductively Coupled Plasma Atomic Emission Spectroscopy The composition of the positive electrode active material powder is measured by inductively coupled plasma (ICP) method using an Agilent 720 ICP-OES. One gram of powder sample is dissolved in 50 mL of high purity hydrochloric acid (at least 37 wt% HCl with respect to the total weight of the solution) in an Erlenmeyer flask. The flask is covered with a watch glass and heated on a hot plate at 380 °C until the powder is completely dissolved. After cooling to room temperature, the solution from the Erlenmeyer flask is poured into a first 250 mL volumetric flask. The first volumetric flask is then filled with deionized water up to the 250 mL mark, followed by thorough homogenization (first dilution). An appropriate amount of the solution is removed from the first volumetric flask with a pipette and transferred to a second 250 mL volumetric flask for the second dilution, followed by homogenization after filling the second volumetric flask with the internal standard components and 10% hydrochloric acid up to the 250 mL mark. Finally, this solution is used for ICP-OES measurement.

[0033] 1.2.Compressed Density The pressed density is measured as follows: 3 grams of powder are loaded into a pellet die with a diameter "d" of 1.30 cm. A uniaxial load of 207 MPa pressure is applied to the powder in the pellet die for 30 seconds. After the load is released, the thickness "t" of the pressed powder is measured. The pellet density (PD) is:

[0034]

number

[0035] 1.3. Scanning Electron Microscopy-Dispersive X-ray Spectroscopy (SEM-EDS) The morphology of the positive electrode active material is analyzed by scanning electron microscopy (SEM) technique. This measurement is 9.6×10 -5 This is performed using a JEOL JSM7100F under a high vacuum environment of 100 Pa.

[0036] The concentrations of Co, Al, Mg and Ti on the surface of the secondary particles of the cathode material are analyzed by energy dispersive X-ray spectroscopy (EDS). The EDS is a 50 mm Oxford instruments 2The EDS analysis of the cathode active material particles was performed using a JEOL JSM 7100F SEM equipped with an X-MaxN EDS sensor. The EDS analysis of the cathode active material particles provides a quantitative elemental analysis of the particles.

[0037] 1.4.Particle size distribution 1.4.1. Measurement of particle size analysis by laser diffraction The particle size distribution (PSD) of the cathode active material powders 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. Sufficient ultrasonic irradiation and stirring are applied and appropriate surfactants are introduced to improve the dispersion of the powders. The median diameter D50 is defined as the particle size at 50% of the cumulative volume percent distribution obtained from the Malvern Mastersizer 3000 measurement with Hydro MV.

[0038] The first and second LCO particle sizes can be determined visually from peaks in the measured particle size distribution, for example as measured by laser diffraction. The volume fraction of the second LCO powder can be determined by the ratio of the area under the curve for the second LCO powder divided by the total area under the curve for both the first and second LCO powders. Known peak deconvolution algorithms can be used if desired.

[0039] 1.4.2. Particle size analysis by SEM The diameter of the primary particles is calculated by using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA) according to the following steps. Step 1) Open the file containing the SEM image of the positive electrode active material at 1000x magnification. Step 2) Set the scale according to the magnification of the SEM. Step 3) For at least 50 particles, use the polygon selection tool to draw a line along the edge of the primary particles. Exclude particles at the edge of the image if they are truncated. Step 4) Measure the area of ​​the selected, drawn primary particle using the measurement settings and area box. Step 5) Assuming the particles are spherical,

[0040]

number

[0041] An example of the calculation of the primary particle size of the 2nd LCO of EX1 by this method is shown in Figure 1 d.

[0042] 1.5.Surface area The specific surface area (SA) of the positive electrode active material is measured by the Brunauer-Emmett-Teller (BET) method using a Micromeritics Tristar II 3020. To remove adsorbed species, the powder sample is heated at 300 °C for 1 h before the measurement under nitrogen (N2) gas. The dried powder is placed in a sample tube. The sample is then degassed at 30 °C for 10 min. The nitrogen adsorption test is performed at 77 K in this instrument. The nitrogen adsorption / desorption isotherm curves are obtained to determine the m 2 The total specific surface area of ​​the sample in units of / g is derived.

[0043] 1.6.Coin Cell 1.6.1. Preparation of Coin Cells The coin cells used in the float test analysis are constructed according to the following steps.

[0044] Step 1) Preparation of the cathode: A solid containing LCO cathode active material powder, conductor (Super P, Timcal) and binder (KF#9305, Kureha) in a weight ratio of 90:5:5 was mixed with a solvent (NMP, Sigma-Aldrich) in a high-speed homogenizer to obtain a homogenized slurry. The homogenized slurry was spread on one side of an aluminum foil using a doctor blade coater with a gap of 230 μm, and the aluminum foil coated with the slurry was dried in an oven at 120 °C, then pressed using a calendar tool and dried again in a vacuum oven to completely remove the solvent.

[0045] Step 2) Coin cell assembly: The coin cells are assembled in a glove box filled with inert gas (argon). For discharge capacity analysis, one separator (Celgard) is placed between the cathode and graphite used as the anode. For float test, two separators are placed between the cathode and anode. 1M LiPF6 in EC:DMC (1:2 by volume) is used as the electrolyte and dropped between the separator and the electrodes. The coin cells are then completely sealed to prevent electrolyte leakage.

[0046] 1.6.2. Float Test Analysis The floating test analyzes the stability of the LCO compound crystals at high temperatures and voltages.

[0047] The fabricated coin cells are tested according to the following charging protocol: first, charge in constant current mode to 4.5 V using a C / 20 rate (1 C=160 mAh / g) in a chamber at 50° C. Then, place the coin cells at constant voltage (4.5 V) for 5 days (120 h).

[0048] Once a side reaction or metal dissolution occurs, the voltage drops. The electrochemical instrument automatically compensates for the (lost) current to keep the voltage constant. The recorded current is therefore a measure of the side reactions taking place during the cycle.

[0049] The specific floating capacity (QF) is the total capacity (mAh / g) during the float test. After the float test, the coin cell is disassembled. The anode and the separator (adjacent to the anode) are analyzed by ICP-OES for metal dissolution analysis. The measured cobalt content is normalized by the total amount of active material in the electrode to obtain the specific cobalt dissolution value.

[0050] 1.7.Full Cell 1.7.1. Description of full cell preparation A 2000mAh pouch-type battery is fabricated as follows. That is, a positive electrode material powder, carbon black (LITX200, Carbot) and MWCNT (LB-107, Cnano) as a positive electrode conductive agent, and polyvinylidene fluoride (PVdF, S5130 available from Solvay) as a positive electrode binder are added to NMP (N-methyl-2-pyrrolidone) as a dispersion medium. The mass ratio of the positive electrode material powder, carbon black, MWCNT, and binder is 97.8 / 0.5 / 0.7 / 1. The mixture is then kneaded to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry is then applied to both sides of a positive electrode current collector made of aluminum foil with a thickness of 20 μm for a 2000mAh pouch-type battery. The weight of the positive electrode active material carried is about 17 mg / cm. 2 The electrode is then dried and calendered using a pressure of 5 MPa and a press roll gap of 10 μm. The typical electrode density is 4.1 g / cm 3 In addition, an aluminum plate that functions as a positive electrode current collector tab is arc-welded to the end of the positive electrode.

[0051] A commercially available anode is used. Briefly, a mixture of graphite, carbon black (Super P), CMC (sodium carboxymethyl cellulose) and SBR (styrene butadiene rubber) in a mass ratio of 96 / 1 / 1.5 / 2.5 is applied to both sides of a copper foil. A nickel plate is arc-welded to the end of the anode to serve as the anode current collector tab.

[0052] A sheet-shaped positive electrode, a sheet-shaped negative electrode, and a sheet-shaped conventional separator (e.g., a ceramic-coated separator having a thickness of 13 μm and a porosity of 30% to 50%, preferably 39 to 44%) sandwiched therebetween are wound using a core rod to obtain a wound electrode body. Next, the wound electrode body and the electrolyte are placed in an aluminum laminate pouch in a dry air chamber with a dew point of −50° C. to prepare a flat pouch-type rechargeable lithium battery. The design capacity of the rechargeable battery is 2000 mAh when charged to 4.45 V.

[0053] The non-aqueous electrolyte is allowed to soak for 8 hours at room temperature. The battery is precharged to 15% of its theoretical capacity and aged at room temperature for 1 day. The battery is then degassed and the aluminum pouch is sealed. The battery is prepared for use as follows: Charge the battery in CC mode (constant current) with a current of 0.2C (where 1C=2000mA) to 4.45V, then in CV mode (constant voltage) until a cut-off current of C / 20 is reached. Then discharge the battery in CC mode at a 0.2C rate to a cut-off voltage of 3.0V.

[0054] 1.7.2.Bulge test method The pouch-type battery prepared by the above preparation method is fully charged to 4.45V, heated to 90℃ in an oven, and then left for 20 hours. At 90℃, the charged cathode reacts with the electrolyte to generate gas. The generated gas causes expansion. The change in thickness ((thickness before and after storage) / thickness before storage) is recorded every hour.

[0055] 2. Examples and Comparative Examples Example 1 A positive electrode active material labeled EX1 is prepared according to the following steps. Step 1) Prepare the single crystal positive electrode active material EX1-A according to the procedure below. a. First Mix: Co3O4 powder having a D50 of 20 μm is mixed with Li2CO3, Al2O3, and MgO to obtain a first mixture with a lithium to metal (Li / (Al+Co)) ratio of 1.05, an Al / Co molar ratio of 0.015, and an Mg / Co molar ratio of 0.005. b. First heating: The first mixture of step 1.a) is heated in a furnace under dry air atmosphere at 1050° C. for 12 hours to obtain a first heating powder. c. Post-treatment: The first heated powder of step 1.c) is pulverized and sieved to obtain EX1-A.

[0056] Step 2) Prepare the single crystal positive electrode active material EX1-B according to the procedure below. a. Second Mix: Co3O4 powder having a D50 of 6 μm is mixed with Li2CO3, Al2O3, and MgO to obtain a second mixture with a lithium to metal (Li / (Al+Co)) ratio of 1.05, an Al / Co molar ratio of 0.015, and an Mg / Co molar ratio of 0.005. b. Second heating: The second mixture of step 2.a) is heated in a furnace under dry air atmosphere at 1050° C. for 12 hours to obtain a second heating powder. c. Post-treatment: The second heated powder of step 1.c) is ground and sieved to obtain EX1-B.

[0057] Step 3) Prepare EX1, which is a mixture of single crystal EX1-A and single crystal EX1-B, according to the procedure below. Third mixture: EX1-A, EX1-B, COH and TiO2 are mixed to obtain a third mixture with a weight ratio of EX1-A:EX1-B=80%:20%, a Li / (Co+Al) molar ratio of 1.00, and a Ti / Co molar ratio of 0.0015. COH is a Co 0.980 Al 0.015 Mg 0.005 (OH)2 powder. b. Third heating: The third mixture of step 4.a) is heated in a furnace under dry air atmosphere at 1050° C. for 12 hours to obtain a third heating powder. c. Post-treatment: The third heated powder of step 4.c) is pulverized and sieved to obtain EX1-B.

[0058] Comparative Example 1 A positive electrode active material labeled CEX1 is prepared according to the following steps. Step 1) Prepare the single crystal positive electrode active material CEX1-A according to the procedure below. a. First Mix: Co3O4 powder having a D50 of 2 μm is mixed with Li2CO3, MgO, and TiO2 to obtain a first mixture with a lithium-to-metal (Li / Co) ratio of 1.06, a Mg / Co molar ratio of 0.0025, and a Ti / Co molar ratio of 0.0008. b. First heating: The first mixture of step 1.a) is heated in a furnace under a dry air atmosphere at 1000° C. for 12 hours to obtain a first heating powder. c. Post-treatment: The first heated powder of step 1.c) is ground and sieved to obtain CEX1-A.

[0059] Step 2) Prepare CEX1, a mixture of CEX1-A and Co3O4, by following the procedure below. a. Second Mix: CEX1-A, Li2CO3, Co3O4, MgO, TiO2 and Al2O3 are mixed to obtain a second mixture with Li / Co molar ratio of 1.00, Mg / Co molar ratio of 0.01, Ti / Co molar ratio of 0.0028 and Al / Co molar ratio of 0.01, where 13 mol% Co is added compared to the Cobalt in CEX1-A. b. Second heating: The second mixture of step 2.a) is heated in a furnace under dry air atmosphere at 980° C. for 10 hours to obtain a second heating powder. c. Post-treatment: The second heated powder of step 2.c) is ground and sieved to obtain CEX1.

[0060] CEX1 is from WO'780.

[0061] Comparative Example 2 The positive electrode active material, labeled CEX2, is prepared according to the following steps. Step 1) Prepare the single crystal positive electrode active material CEX2-A according to the procedure below. a. First Mix: Co3O4 powder having a D50 of 20 μm is mixed with Li2CO3, Al2O3, and MgO to obtain a first mixture with a lithium to metal (Li / (Al+Co)) ratio of 1.03, an Al / Co molar ratio of 0.015, and an Mg / Co molar ratio of 0.005. b. First heating: The first mixture of step 1.a) is heated in a furnace under dry air atmosphere at 1050° C. for 12 hours to obtain a first heating powder. c. Post-treatment: The first heated powder of step 1.c) is ground and sieved to obtain CEX2-A.

[0062] Step 2) Prepare CEX2-B, which is Co3O4 containing Al and Mg, according to the procedure below. a. Second Mix: Co3O4 powder with D50 of about 2 μm is mixed with Al2O3 and MgO to obtain a second mixture with Al / Co molar ratio of 0.015 and Mg / Co molar ratio of 0.005. b. Second Heating: The mixture of step 2.a) is heated in a furnace under dry air atmosphere at 800° C. for 12 hours to obtain CEX2-B.

[0063] Step 3) Prepare CEX2, which is a mixture of single crystal CEX2-A and polycrystalline CEX2-B, by following the procedure below. a. Third Mixture: CEX2-A, CEX2-B, Li2CO3, and TiO2 are mixed to obtain a third mixture with a Li / (Co+Al) molar ratio of 1.00 and a Ti / Co molar ratio of 0.0015, in which 15 mol% Co is added compared to the Cobalt in CEX2-A. b. Third heating: The third mixture of step 3.a) is heated in a furnace under dry air atmosphere at 980° C. for 12 hours to obtain a second heating powder. c. Post-treatment: The second heated powder of step 3.c) is ground and sieved to obtain CEX2.

[0064] [Table 1]

[0065] [Table 2]

[0066] Table 1 summarizes the first and second LCO powder components of EX1, CEX1, and CEX2. EX1 contains first and second LCO powders with single crystal morphology as shown by the SEM image in Figure 1a. On the other hand, CEX1 and CEX2 are mixtures of a first single crystal LCO powder and a second polycrystalline LCO powder. The SEM images of CEX1 and CEX2 are shown in Figures 1b and 1c, respectively.

[0067] Figure 4 shows the distribution graph of the particle size analysis of EX1. From the graph, the first median diameter D50 A is about 21 μm, and the second median diameter D50 B The volume fraction of the second LCO powder is 19.2 vol%.

[0068] Table 2 summarizes the composition, specific surface area, pressed density and electrochemical test results of the examples and comparative examples. EX1 shows the lowest specific surface area SA compared to CEX1 and CEX2. The low specific surface area corresponds to low QF, low Co. Dis EX1 is associated with high stability at high temperature and voltage as indicated by its low T4h and low T4h. In addition, EX1 exhibits a high packed density PA compared to CEX1 and CEX2. The superior performance of EX1 in stability and density comes from its compositional mixture containing a large first LCO single crystal powder and a small second LCO single crystal powder.

[0069] It is concluded that EX1 meets the objectives of the present invention to provide a positive electrode active material that is stable in high temperature and high voltage electrochemical cell applications and has high packed density.

Claims

1. A positive electrode active material for a rechargeable lithium ion battery, comprising: the positive electrode active material comprises Li, Co, O, and optionally M', where M' comprises Al and / or Ti, and optionally one or more elements selected from Ni, Mn, B, Sr, Mg, Nb, W, F, and Zr, and a molar ratio of Co to M'+Co (Co / (M'+Co)) is greater than 0.90 as determined by ICP-OES analysis; the positive electrode active material includes a first LCO powder and a second LCO powder, both of which are single crystal powders; The first LCO powder has a first median diameter D50 of 12 μm to 25 μm as determined by laser diffraction particle size analysis. Ａ having The second LCO powder has a second median diameter D50 of 3 μm to 8 μm as determined by laser diffraction particle size analysis. Ｂ having a volume fraction of the second LCO powder relative to the total volume of the cathode active material is 10% to 40% as determined by laser diffraction particle size analysis.

2. The cathode active material of claim 1 , wherein the cathode active material comprises M′.

3. The positive electrode active material according to claim 1 or 2, wherein M′ contains Al and Ti.

4. 4. The cathode active material of claim 1, wherein the second LCO powder comprises a powder having an average primary particle size of 3 μm to 7 μm as determined by SEM analysis.

5. The positive electrode active material has a thickness of 0.10 m as determined by BET analysis. ２ / g to 0.25m ２ The positive electrode active material according to any one of claims 1 to 4, having a specific surface area of ​​1 / g.

6. The positive electrode active material had a compressibility of 3.9 g / cm after applying a uniaxial pressure of 207 MPa for 30 seconds. ３ ~4.3g / cm ３ The positive electrode active material according to any one of claims 1 to 5, having a compressed density of

7. 7. The positive electrode active material according to claim 6, wherein the ratio of the compressed density to the specific surface area is 19.0 to 28.

0.

8. The positive electrode active material according to any one of claims 1 to 7, wherein the positive electrode comprises M', and M' comprises Ti and / or Mg.

9. 9. The active cathode material of claim 1, wherein the first LCO powder comprises particles having Ti and / or Mg rich islands on the surface of the particles as determined by SEM-EDS elemental mapping.

10. 10. The active cathode material of claim 1, wherein the first LCO powder comprises particles having Ti and Mg rich islands on the surface of the particles as determined by SEM-EDS elemental mapping.

11. 11. The cathode active material of claim 10, wherein the Ti and Mg rich islands have a diameter of 0.2 μm to 3.0 μm as determined by SEM analysis.

12. The second median diameter D50 Ｂ The positive electrode active material according to any one of claims 1 to 11, wherein the thickness is 5 µm to 7 µm.

13. The positive electrode active material according to any one of claims 1 to 12, wherein the volume fraction of the second LCO powder relative to the total volume of the positive electrode active material is 15% to 30%.

14. the positive electrode material comprises Li, Co, metal M', and O, the metal M' comprises Al, Ti, and Mg; The positive electrode active material according to any one of claims 1 to 13, wherein the molar ratio of Al to Co (Al / Co) is 0.001 to 0.030, the molar ratio of Mg to Co (Mg / Co) is 0.001 to 0.020, and the molar ratio of Ti to Co (Ti / Co) is 0.001 to 0.005, as determined by ICP-OES analysis.

15. 15. The cathode active material of claim 1, wherein the cathode material has a specific stray capacity of 10 mAh / g to 150 mAh / g as determined by electrochemical analysis at 4.5 V and 50° C. for 120 hours.

16. A method for producing the positive electrode active material according to any one of claims 1 to 15, comprising the following steps: 1) Median diameter D50 of 12 μm to 25 μm Ａ A first lithium cobalt-based metal oxide powder having a median diameter D50 of 3 μm to 8 μm. Ｂ A second lithium cobalt-based metal oxide powder having TiO ２ a mixing step of obtaining a mixture, wherein the first lithium-cobalt-based metal oxide powder and the second lithium-cobalt-based metal oxide powder are both single crystal powders, and a weight fraction of the second lithium-cobalt-based metal oxide relative to the total weight of the positive electrode active material is 10% to 40%; 2) heating the mixture at a temperature between 700° C. and 1100° C. for a period of between 5 hours and 20 hours.

17. Step 1) is a process for producing a granular material having a median diameter D50 of 12 μm to 25 μm. Ａ A first lithium cobalt-based metal oxide powder having a median diameter D50 of 3 μm to 8 μm. Ｂ A second lithium cobalt-based metal oxide powder having a median diameter D50 of less than 300 nm. Ｃ and a Co-based compound having TiO ２ and obtaining a mixture, wherein the first lithium-cobalt-based metal oxide powder and the second lithium-cobalt-based metal oxide powder are both single crystal powders, and the weight fraction of the second lithium-cobalt-based metal oxide relative to the total weight of the positive electrode active material is 10% to 40%.

18. The Co-based compound has a median diameter D50 of less than 150 nm. Ｃ and the Co-based compound comprises Al and / or Mg.

19. A battery cell comprising the positive electrode active material according to any one of claims 1 to 15.

20. 20. Use of the battery of claim 19 in any of a portable computer, a tablet, a mobile phone, a power tool, an electric vehicle, and an energy storage system.

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