Patent Application
20240038982
The present invention relates to a positive electrode active material for lithium-ion rechargeable batteries. More specifically, the invention relates to particulate positive electrode active materials comprising Al and B elements; a battery comprising said particulate positive electrode active materials comprising Al and B elements; and, use of said positive electrode active material in a battery in either one of portable computer, a tablet, a mobile phone, an electrically powered vehicle, and an energy storage system.
This invention relates to a single-crystalline positive electrode active material powder for lithium-ion rechargeable batteries (LIBs), comprising the elements Al and B.
Positive electrode active materials comprising Al and B elements are already known, for example from US 2016/336595. The document US 2016/336595 discloses a positive electrode active material powder made from a mixture of a lithium nickel manganese cobalt oxide (NMC) powder, Al(OH)3 powder, and B2O3 powder heated at 400° C. The Ni content in the NMC is around 60 mol %. However, the positive electrode active material according to US 2016/336595 has low initial discharge capacity (DQ1) and high irreversible capacity (IRRQ).
It is therefore an object of the present invention to provide a positive electrode active material having a higher DQ1 and a lower IRRQ than known materials. In particular, it is an object of the present invention to provide a positive electrode active material which preferably has DQ1 higher than 215.0 mAh/g and IRRQ lower than 9.5% when the molar ratio of Ni to M′ is higher than 80 mol % as obtained by the analytical method of the present invention and preferably at least 185 mAh/g and IRRQ lower than 12% when the molar ratio of Ni to M′ is at least 70 mol % as obtained by the analytical method of the present invention.
This objective is achieved by providing a positive electrode active material for lithium-ion rechargeable batteries, wherein the positive electrode active material is a powder, wherein the positive electrode active material comprises Li, M′, and oxygen, wherein M′ comprises:
wherein the powder is a single-crystalline powder.
It is indeed observed that a higher DQ1 and a lower IRRQ is achieved using a positive electrode active material according to the present invention, as illustrated by examples and supported by the results provided in Table 3.
Further, in a first aspect the present invention provides an electrochemical cell comprising a positive electrode active material according to the first aspect of the invention, in a second aspect, the present invention provides a battery cell comprising a positive electrode active material according to the first aspect of the invention and in a third aspect the present invention a use of a positive electrode active material according to the first aspect of the invention in a battery.
By means of further guidance, a figure is included to better appreciate the teaching of the present invention. Said figure is intended to assist the description of the invention and is nowhere intended as a limitation of the presently disclosed invention.
Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention. As used herein, the following terms have the following meanings:
The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints. All percentages are to be understood as percentage by weight, abbreviated as “wt. %”, unless otherwise defined or unless a different meaning is obvious to the person skilled in the art from its use and in the context wherein it is used.
“About” as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/−20% or less, preferably +/−10% or less, more preferably +/−5% or less, even more preferably +/−1% or less, and still more preferably +/−0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier “about” refers is itself also specifically disclosed.
The term ‘ppm’ is as used in this document means parts per million on a mass basis.
The term “median particle size D50”, as defined herein, can be interchangeably used with the terms “D50” or “d50” or “median particle size” or “a median particle size (d50 or D50)”. D50 is defined herein as the particle size at 50% of the cumulative volume % distributions. D50 is typically determined by laser diffraction particle size analysis.
The term “at %”, as defined herein, is equivalent to the term “atomic percent” and signifies atomic percentage. The term “at %” of a given element expression of a concentration means how many percent of all atoms in the concerned compound are atoms of said element. The term “at %” is equivalent to the terms “mol %” or “molar percent”.
A positive electrode active material is defined as a material which is electrochemically active in a positive electrode. By active material, it must be understood a material capable to capture and release Li ions when subjected to a voltage change over a predetermined period of time.
In a first aspect, the present invention provides a positive electrode active material for lithium-ion rechargeable batteries, wherein the positive electrode active material is a powder, wherein the positive electrode active material comprises Li, M′, and oxygen, wherein M′ comprises:
A single-crystalline powder is considered to be a powder in which 80% or more of the particles in a field of view of at least 45 μm×at least 60 μm (i.e. of at least 2700 μm2), preferably of: at least 100 μm×100 μm (i.e. of at least 10,000 μm2) in a SEM image have a single-crystalline morphology.
A particle is considered to have single-crystalline morphology if it consists of only one grain, or a very low number of a most five, constituent grains, as observed by SEM or TEM. For instance, particles with single-crystalline morphology are shown in
For the determination of single-crystalline morphology of particles, grains which have a largest linear dimension as observed by SEM which is smaller than 20% of the median particle size D50 of the powder as determined by laser diffraction are ignored. This avoids that particles which are in essence single-crystalline, but which may have deposited on them several very small other grains, are inadvertently considered as not having a single-crystalline morphology.
A positive electrode active material for lithium-ion rechargeable batteries according to the present invention indeed has improved electrochemical properties when used in an electrochemical cell allowing a higher DQ1 and lower IRRQ to be achieved. This is illustrated by examples and the results provided in the Table 3.
The XPS analysis provides atomic content of elements in an uppermost layer of a particle with a penetration depth of about 10.0 nm from an outer boundary of the particle. The outer boundary of the particle is also referred to as “surface”.
The composition of the positive electrode active material particle can be expressed as the indices a, x, y, z, a, and d in a general formula Li1+b(NiaMnyCoxAcDz)1-bO2, according to the stoichiometry of the elements determined by known analysis methods, such as ICP-OES (Inductively coupled plasma-optical emission spectrometry, also referred hereafter as ICP) and IC (ion chromatography). ICP analysis provides the weight fraction of elements in a positive electrode active material particle.
Preferably, the positive electrode active material has a nickel content a, relative to M′, of more than 75.0 mol %, and more preferably at least 80.0 mol %, as measured by ICP.
Preferably, the positive electrode active material has a cobalt content x, relative to M′, of at least 1 mol %, more preferably at least 2 mol % or even more preferably at least 3 mol %, as measured by ICP. The present invention provides a positive electrode active material which has a cobalt content x of 3.0, 5.0, 7.0, 9.0, or 10.0 mol %, relative to M′, as measured by ICP, or any value there in between.
Preferably, the positive electrode active material has a manganese content y, relative to M′, of at least 1 mol %, more preferably at least 2 mol % or even more preferably at least 3 mol %, as determined by ICP. The present invention provides a positive electrode active material which has a manganese content y of 3.0, 5.0, 7.0, 9.0, or 10.0 mol %, relative to M′, as measured by ICP, or any value there in between.
Preferably, the present invention provides a positive electrode active material wherein a molar ratio of lithium to the total molar amount of nickel, manganese, and/or cobalt is 0.95≤Li:Me≤1.10 wherein Me is a total molar fraction of Ni, Mn, and/or Co.
Preferably, the present invention provides a positive electrode active material according to the first aspect of the invention, wherein the total content of Al and B relative to M′ as measured by ICP, is preferably at least 0.1 mol %, and more preferably at least 0.4 mol %, relative to M′. The total content of Al and B relative to the M′ as measured by ICP, is preferably at most 2.0 mol %.
Preferably, the positive electrode active material of the present comprises Al and B and W, each in a content of at least 0.02 mol % relative to M′, as measured by ICP.
Preferably, AlA is between 0.025 mol % and 2.0 mol %, is expressed as a molar fraction compared to the sum of a and x and y, as measured by ICP.
Preferably, BA is between 0.025 mol % and 2.0 mol %, are expressed as molar fractions compared to the sum of a and x and y, as measured by ICP.
Preferably, the positive electrode active material of the present invention has a W content WA, wherein WA is determined by ICP analysis and expressed as molar fraction compared to the sum of a and x and y, wherein the positive electrode active material, when measured by XPS analysis, shows an average W fraction WB, wherein WB is expressed as molar fraction compared to the sum of the fractions of Co, Mn and Ni as measured by XPS analysis, wherein the ratio WB/WA>1.0.
Preferably, WA is between 0.025 mol % and 2.0 mol %, are expressed as molar fractions compared to the sum of a and x and y, as measured by ICP.
Preferably, BA is at least 0.0009, in other words at least 0.09 mol %, and more preferably BA is at least 0.0018, in other words at least 0.18 mol %, are expressed as molar fractions compared to the sum of a and x and y, as measured by ICP.
Preferably, AlA is at most 0.008, in other words at most 0.8 mol %, are expressed as molar fractions compared to the sum of a and x and y, as measured by ICP.
In preferred embodiments:
In more preferred embodiments:
In even more preferred embodiments:
Preferably, the ratio WB/WA>10, and more preferably the ratio WB/WA>50, and most preferably the ratio WB/WA>115.
In a preferred embodiment the ratio WB/WA<500.
Preferably, the present invention provides a positive electrode active material according to the first aspect of the invention, wherein the positive electrode active material has a median particle size (d50 or D50) of 2.0 μm to 9.0 μm, as determined by laser diffraction. The median particle size (d50 or D50) can be measured with a Malvern Mastersizer 3000. Preferably, said median particle size is between 2.0 μm and 8.0 μm, more preferably between 3.0 μm and 7.0 μm, and most preferably about 4.0 μm.
Preferably, the present invention provides a positive electrode active material according to the first aspect of the invention, wherein said positive electrode active material has a DQ1 of at least 215 mAh/g and IRRQ of at most 9.5%, when the molar ratio of Ni to M′ is higher than 80 mol %, and more preferably said positive electrode active material has a DQ1 of at least 185 mAh/g and IRRQ of at most 12%, when the molar ratio of Ni to M′ is between 70 mol % and 75 mol %. Said DQ1 and IRRQ are determined by a coin cell testing procedure using a 1C current definition of 220 mAh/g when the molar ratio of Ni to M′ is higher than 80 mol. % and 1C current definition of 160 mA/g in the 4.4-3.0 V/Li metal window range. The testing procedure is further described in § 1.3 and included hereby by reference.
Preferably, the positive electrode active material according to the first aspect of the invention comprises LiAlO2, Al2O3, and Li—B—O compounds as identified by XPS.
In a second aspect, the present invention provides a battery cell comprising a positive electrode active material according to the first aspect of the invention.
In a third aspect, the present invention provides a use of a positive electrode active material according to the first aspect of the invention in a battery of either one of a portable computer, a tablet, a mobile phone, an electrically powered vehicle, and an energy storage system.
The following examples are intended to further clarify the present invention and are nowhere intended to limit the scope of the present invention.
The composition of a positive electrode active material powder is measured by the inductively coupled plasma (ICP) method using an Agilent 720 ICP-OES (Agilent Technologies, https://www.agilent.com/cs/library/brochures/5990-6497EN%20720-725_ICP-OES_LR.pdf). 1 gram of powder sample is dissolved into 50 mL of high purity hydrochloric acid (at least 37 wt. % of HCl with respect to the total weight of solution) in an Erlenmeyer flask. The flask is covered by a watch glass and heated on a hot plate at 380° C. until the powder is completely dissolved. After being cooled to room temperature, the solution from the Erlenmeyer flask is poured into a first 250 mL volumetric flask. Afterwards, the first volumetric flask is filled with deionized water up to the 250 mL mark, followed by a complete homogenization process (1st dilution). An appropriate amount of the solution from the first volumetric flask is taken out by a pipette and transferred into a second 250 mL volumetric flask for the 2nd dilution, where the second volumetric flask is filled with an internal standard element and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this solution is used for ICP measurement.
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 with a Hydro MV wet dispersion accessory (https://www.malvernpanalytical.com/en/products/product-range/mastersizer-range/mastersizer-3000#overview) after having dispersed each of the powder samples in an aqueous medium. In order to improve the dispersion of the powder, sufficient ultrasonic irradiation and stirring is applied, and an appropriate surfactant is introduced. D50 is defined as the particle size at 50% of the cumulative volume % distributions obtained from the Malvern Mastersizer 3000 with Hydro MV measurements.
Coin Cell Preparation for CEX1, EX1.1, EX1.2, CEX2, EX2.1, EX2.2, CEX3, EX3.1, EX3.3
For the preparation of a positive electrode, a slurry that contains a positive electrode active material powder, conductor (Super P, Timcal), binder (KF #9305, Kureha)—with a formulation of 96.5:1.5:2.0 by weight—in a solvent (NMP, Mitsubishi) is prepared by 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 slurry coated foil is dried in an oven at 120° C. and then pressed using a calendaring tool with 10 μm gap.
Then it is dried again in a vacuum oven to completely remove the remaining solvent in the electrode film. A coin cell is assembled in an argon-filled glovebox. A separator (Celgard 2320) is located between a positive electrode and a piece of lithium foil used as a negative electrode. 1 M LiPF6 in EC/DMC (1:2) is used as electrolyte and is dropped between separator and electrodes. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.
Coin Cell Preparation for CEX4, EX4.1, EX4.2, CEX5.1, CEX5.2
For the preparation of a positive electrode, a slurry that contains a positive electrode active material powder, conductor (Super P, Timcal), binder (KF #9305, Kureha)—with a formulation of 90:5:5 by weight—in a solvent (NMP, Mitsubishi) is prepared by a high-speed homogenizer. The homogenized slurry is spread on one side of an aluminum foil using a doctor blade coater with a 230 μm gap. The slurry coated foil is dried in an oven at 120° C. and then pressed using a calendaring tool with 40 μm gap.
Then it is dried again in a vacuum oven to completely remove the remaining solvent in the electrode film. A coin cell is assembled in an argon-filled glovebox. A separator (Celgard 2320) is located between a positive electrode and a piece of lithium foil used as a negative electrode. 1 M LiPF6 in EC/DMC (1:2) is used as electrolyte and is dropped between separator and electrodes. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.
The testing method is a conventional “constant cut-off voltage” test. The conventional coin cell test in the present invention follows the schedule shown in Table 1. Each cell is cycled at 25° C. using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo, http://www.toyosystem.com/image/menu3/toscat/TOSCAT-3100.pdf).
1C current definition for CEX1, EX1.1, EX1.2, CEX2, EX2.1, EX2.2, CEX3, EX3.1, and EX3.3 is 220 mAh/g and for CEX4, EX4.1, EX4.2, CEX5.1, CEX5.2 is 160 mAh/g. The initial charge capacity (CQ1) and discharge capacity (DQ1) are measured in constant current mode (CC) at C rate of 0.1C in the 4.3 V to 3.0 V/Li metal window range.
The irreversible capacity IRRQ is expressed in % as follows:
IRRQ (%)=100%*(CQ1−DQ1)/CQ1
In the present invention, X-ray photoelectron spectroscopy (XPS) is used to analyze the surface of positive electrode active material powder particles. In XPS measurement, the signal is acquired from the first few nanometers (e.g. 1 nm to 10 nm) of the uppermost part of a sample, i.e. surface layer. Therefore, all elements measured by XPS are contained in the surface layer.
For the surface analysis of positive electrode active material powder particles, XPS measurement is carried out using a Thermo K-α+ spectrometer (Thermo Scientific, https://www.thermofisher.com/order/catalog/product/IQLAADGAAFFACVMAHV). Monochromatic Al Kα radiation (hu=1486.6 eV) is used with a spot size of 400 μm and measurement angle of 45°. A wide survey scan to identify elements present at the surface is conducted at 200 eV pass energy. Cis peak having a maximum intensity (or centered) at a binding energy of 284.8 eV is used as a calibrate peak position after data collection. Accurate narrow-scans are performed afterwards at 50 eV for at least 10 scans for each identified element to determine the precise surface composition.
Curve fitting is done with CasaXPS Version 2.3.19PR1.0 (Casa Software, http://www.casaxps.com/) using a Shirley-type background treatment and Scofield sensitivity factors. The fitting parameters are according to Table 2a. Line shape GL(30) is the Gaussian/Lorentzian product formula with 70% Gaussian line and 30% Lorentzian line. LA(α, β, m) is an asymmetric line-shape where α and β define tail spreading of the peak and m define the width.
For Al, B, Co, and W peaks, constraints are set for each defined peak according to Table 2b. Ni3p and W5p3 are not quantified.
Table 2c shows the reference of the maximum peak intensity position range for the Al and B related compounds.
The Al, B, and W surface contents as determined by XPS are expressed as a molar fraction of Al, B, and W, respectively, in the surface layer of the particles divided by the total content of Ni, Mn and Co in said surface layer. It is calculated as follows:
fraction of Al=AlB=Al (at %)/(Ni (at %)+Mn (at %)+Co (at %))
fraction of B=BB=B (at %)/(Ni (at %)+Mn (at %)+Co (at %))
fraction of W=WB=W (at %)/(Ni (at %)+Mn (at %)+Co (at %)).
A single-crystalline positive electrode active material labelled as CEX1 is prepared according to the following steps:
EX1.1 is prepared according to the following process:
Alumina powder in amount ranging from 250 to 1000 ppm Al, with respect to the total weight of the final product, can be added in the Step 2) grinding and sieving process as a free-flowing agent to assist the sieving step.
EX1.2 is prepared according to the same method as EX1.2 except that WO3 powder is added in the Step 1) together with CEX1 to obtain a mixture comprising 500 ppm of B and 4500 ppm of W.
A single-crystalline positive electrode active material labelled as CEX2 is prepared according to the following steps:
EX2.1 is prepared according to the same method as EX1.1 except that CEX2 is used instead of CEX1 in Step 1).
EX2.2 is prepared according to the same method as EX1.2 except that CEX2 is used instead of CEX1 in Step 1).
CEX3 is prepared according to the same method as CEX2 except that a nickel-based transition metal oxidized hydroxide powder (TMH3) having a metal composition Ni0.92Mn0.05Co0.03 is prepared by a co-precipitation process in Step 10.
EX3.1 is prepared according to the same method as EX1.1 except that CEX3 is used instead of CEX1 in Step 1).
EX3.2 is prepared according to the same method as EX1.2 except that CEX3 is used instead of CEX1 in Step 1).
A single-crystalline positive electrode active material labelled as CEX4 is prepared according to the following steps:
EX4.1 is prepared according to the same method as EX1.1 except that CEX4 is used instead of CEX1 in Step 1) and 500 ppm of Al from alumina powder is added in the Step 2).
EX4.1 is prepared according to the same method as EX1.2 except that CEX4 is used instead of CEX1 in Step 1) and 500 ppm of Al from alumina powder is added in the Step 2).
Due to the wet milling, the abovementioned examples and comparative examples are single-crystalline powders.
A single-crystalline positive electrode active material labelled as CEX5.1 is prepared according to the following steps:
Due to the air jet milling in Step 3) CEX 5.1 is a single-crystalline powder.
CEX5.2 is prepared according to the same method as EX1.1 except that CEX5.1 is used instead of CEX1 in Step 1), firing time is 9 hours, and 500 ppm of Al from alumina powder is added in the grinding process of Step 2).
CEX5.2 is according to document US 2016/336595.
Table 3 summarizes the composition of examples and comparative examples and their corresponding electrochemical properties.
Table 4 summarized the XPS analysis result of EX1.1 and EX1.2 showing Al, B, and W molar ratio with respect to the total molar fraction of Ni, Mn, and Co. The table also compares the result with that of ICP. The molar ratio higher than 0 indicating said Al, B, and W are presence in the surface of the positive electrode active material as associated with the XPS measurement which signal is acquired from the first few nanometers (e.g. 1 nm to 10 nm) of the uppermost part of a sample, i.e. surface layer. On the other hand, Al, B, and W molar ratio obtained from ICP measurement is from the entire particles. Therefore, the ratio of XPS to ICP of higher than 0 indicating said elements Al, B, or W presence mostly on the surface of the positive electrode active material. The ratio of XPS to ICP of higher than 0 is observed for Al and B in EX1.1 and Al, B, and W in EX2.2 and EX4.2.
Furthermore, XPS peak location is associated with compounds derived from the preparation process.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20214299.8 | Dec 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP21/85742 | 12/14/2021 | WO |
