Patent Application
20240132373
This invention relates to a lithium nickel-based oxide positive electrode active material for solid-state batteries suitable for electric vehicle (EV) and hybrid electric vehicle (HEV) applications, comprising lithium nickel-based oxide particles comprising zirconium (Zr).
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 the framework of the present invention, at % signifies atomic percentage. The at % or “atom percent” of a given element expression of a concentration means how many percent of all atoms in the claimed compound are atoms of said element. The designation at % is equivalent to mol % or “molar percent”.
The weight percent (wt. %) of a first element E (Ewt1) in a material can be converted from a given atomic percent (at %) of said first element E (Eat1) in said material by applying the following formula:
wherein the product of Eat1 with Eaw1, Eaw1 being the atomic weight (or molecular weight) of the first element E, is divided by the sum of Eati×Eawi for the other elements in the material. n is an integer which represents the number of different elements included in the material.
It is an object of the present invention to provide a positive electrode active material having an improved first charge capacity of at least 160 mAh/g in the solid-state battery.
This objective is achieved by providing a positive electrode active material for solid-state batteries, wherein the positive electrode active material comprises Li, M′, and oxygen, wherein M′ comprises:
wherein the positive electrode active material has a Zr content ZrB, wherein ZrB is determined by XPS analysis, wherein ZrB is expressed as molar fractions compared to the sum of molar fractions of Co, Mn, Ni, and Zr, as measured by XPS analysis,
wherein the ratio ZrB/ZrA>50.0,
wherein the positive electrode active material comprises secondary particles having a plurality of primary particles,
wherein said primary particle has an average diameter of between 170 nm to 340 nm as determined by the method of this invention.
The present invention concerns the following embodiments:
In a first aspect, the present invention concerns a positive electrode active material for solid-state batteries, wherein the positive electrode active material comprises Li, M′, and oxygen, wherein M′ comprises:
wherein the positive electrode active material has a Zr content ZrB, wherein ZrB is determined by XPS analysis, wherein ZrB is expressed in percent as molar fractions compared to the sum of molar fractions of Co, Mn, Ni, and Zr, as measured by XPS analysis,
wherein the ratio ZrB/ZrA>50.0,
Note that ZrA is the Zr content of the positive electrode active material as determined by ICP and expressed as a fraction relative to the sum of the contents of Co, Ni, Mn, and Zr.
Preferably, the ZrB/ZrA ratio is at least 80, preferably at least 100, more preferably at least 130. Preferably, the ZrB/ZrA ratio is at most 500, more preferably at most 300 and most preferably at most 200.
Preferably the positive electrode active material comprises secondary particles having a plurality of primary particles and wherein said primary particles have an average diameter of between 170 nm to 340 nm, preferably between 200 nm to 340 nm, as determined by measuring primary particle size in an image taken by SEM.
More preferably said primary particles have an average diameter of at least 180 nm, preferably 200 nm, preferably 220 nm, even more preferably of at least 225 nm.
Preferably said primary particles have an average diameter of at most 330 nm, preferably of at most 320 nm, more preferably of at most 300 nm, even more preferably of at most 250 nm.
Preferably said primary particles have an average diameter of between 180 nm and 330 nm, preferably between 200 nm and 320 nm, more preferably between 220 nm and 310 nm, even more preferably between 225 nm and 250 nm.
As appreciated by the skilled person the primary particle size is determined by measuring the particle size of the primary particle in an image taken by SEM.
Preferably, x≥55.0 mol % and more preferably x≥60.0 mol %
Preferably, y>0 mol % and more preferably y≥5.0 mol and even more preferably y≥10.0 mol %
In another embodiment, said Ni in a content x is between 55 mol % and 72 mol % relative to M′ and said Co in a content y is between 0.0 mol % and 20.0 mol % relative to M′.
In a preferred embodiment Ni is in a content x≥55.0 mol %, preferably x≥60.0 mol %, more preferably x≥62.0 mol %. In a preferred embodiment, x≤72.0 mol % preferably x≤70.0 mol % and more preferably x≤68.0 mol %.
In a more preferred embodiment Ni is in a content x between 55.0 mol %≤x≤72.0 mol %, preferably 60.0 mol %≤x≤70.0 mol %, more preferably 62.0 mol %≤x≤68.0 mol %.
As appreciated by the skilled person the amount of Li and M′, preferably Li, Ni, Mn, Co, D and Zr in the positive electrode active material is measured with Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). For example, but not limiting to the invention, an Agilent ICP 720-ES is used in the ICP-OES analysis.
In a preferred embodiment Mn is in a content z>0.0 mol %, more preferably z≥5.0 mol %, and even more preferably z≥8.0 mol %. In a preferred embodiment the content is z≤40.0 mol %, preferably z≤30.0 mol %, and more preferably z≤25.0 mol %. In a preferred embodiment the content is 0.0 mol %<z≤40.0 mol %, preferably 5.0 mol %≤z≤30.0 mol %, more preferably 8.0 mol %≤z≤25.0 mol %.
In a preferred embodiment Co is in a content y>0.0 mol %, more preferably y≥1.0 mol %, and even more preferably y≥3.0 mol %. In a preferred embodiment the content is y≤40.0 mol %, more preferably y≤30.0 mol %, and even more preferably y≤25.0 mol %. In a preferred embodiment the content is 0.0 mol %<y≤40.0 mol %, preferably 1.0 mol %≤y≤30.0 mol %, more preferably 3.0 mol %≤y≤25.0 mol %.
In a preferred embodiment D comprises at least one element of the group consisting of: Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, and Zn; preferably Al, B, Cr, Nb, S, Si, Ti, Y and W.
In a preferred embodiment D is in a content a>0.0 mol %, more preferably a≥0.25 mol %, and even more preferably a≥0.5 mol %. In a preferred embodiment the content is a≤2.0 mol %, preferably a≤1.75 mol %, and more preferably a≤1.5 mol %. In a preferred embodiment the content is 0.0 mol %<z≤2.0 mol %, preferably 0.25 mol %≤z≤1.75 mol % and more preferably 0.5 mol %≤z≤1.5 mol %.
As appreciated by the skilled person the secondary particles comprise of a plurality of primary particles, preferably more than 20 primary particles, preferably more than 10 primary particles, most preferably more than 5 primary particles. Primary particles are particles which are individual crystals or which are formed of less than five, and preferably at most three, primary particles which are themselves individual crystals. This can be observed in proper microscope techniques like Scanning Electron Microscope (SEM) by observing grain boundaries.
In a second embodiment, preferably according to the Embodiment 1, wherein the Zr content ZrA is b/(b+x+y+z) is at least 0.10 mol % and at most 1.00 mol %. Preferably, the Zr content ZrA is b/(b+x+y+z) is at least 0.20 mol % and at most 0.80 mol %. Most preferably the Zr content ZrA is b/(b+x+y+z) is at least 0.30 mol % and at most 0.70 mol %. In an alternative but even preferred embodiment, the Zr content ZrA is b/(b+x+y+z) is at least 0.10 mol % and at most 1.50 mol %. Preferably, the Zr content ZrA is b/(b+x+y+z) is at least 0.20 mol % and at most 1.00 mol %. Most preferably the Zr content ZrA is b/(b+x+y+z) is at least 0.30 mol % and at most 0.90 mol %.
In a preferred embodiment, Zr is in a content b of at least 0.10 mol % and at most 1.00 mol % relative M′, more preferably at least 0.20 mol % and at most 0.80 mol % relative to M′, most preferably at least 0.30 mol % and at most 0.70 mol % relative M′.
In an alternative but even preferred embodiment Zr is in a content b of at least 0.10 mol % and at most 1.50 mol % relative M′, more preferably at least 0.20 mol % and at most 1.00 mol % relative to M′, most preferably at least 0.30 mol % and at most 0.90 mol % relative M′.
In a preferred embodiment the Zr content ZrB is more than 0.25 mol %, preferably more than 0.50 mol %, most preferably more than 0.60 mol %. In a preferred embodiment ZrB is less than 2.0 mol %, preferably less than 1.5 mol %, more preferably less than 1.0 mol %. In a preferred embodiment ZrB is between 0.25 mol % and 2.0 mol %, preferably between 0.50 mol % and 1.5 mol %, most preferably between 0.60 mol % and 1.0 mol %. As appreciated by the skilled person ZrB is expressed as molar fraction, as measured by XPS analysis compared to the sum of molar fractions of Co, Mn, Ni, and Zr, as measured by XPS analysis.
In a third embodiment, according to Embodiment 1 to 2, said material has a secondary particle median size D50 of at least 2 μm, and preferably of at least 5 μm as determined by laser diffraction particle size analysis.
Preferably, said material has a secondary particle median size D50 of at most 15 μm, and preferably of at most 13 μm as determined by laser diffraction particle size analysis.
For example, but not limiting to the invention, the laser diffraction particle size analysis is performed by a Malvern Mastersizer 3000.
In a fourth embodiment, according to Embodiment 1 to 3, said material has a carbon content of at least 600 ppm, preferably of at least 650 ppm, more preferably of at least 750 ppm and most preferably at least 900 ppm as determined by carbon analyzer.
Preferably, said material has a carbon content of at most 5000 ppm, preferably of at most 3000 ppm, more preferably of at most 1500 ppm and most preferably of at most 1100 ppm as determined by carbon analyzer.
In a fifth embodiment, according to any Embodiment 1 to 4, wherein the thickness of Zr>10 nm. Preferably, the thickness is ≥15 nm and more preferably ≥20 nm as determined by TEM-EDS measurement. Preferably the thickness of Zr is ≤100 nm, preferably the thickness is ≤50 nm, more preferably the thickness is ≤30 nm. Preferably the thickness of Zr is between 10 nm and 100 nm, preferably between 15 nm and 50 nm, more preferably between 22 nm and 28 nm.
In the framework of this invention, the (minimum) thickness of the surface layer is defined as the shortest distance between a first point located at a periphery of a cross-section of a particle and a second point located in a line defined between said first point and a geometric center (or centroid) of said particle, wherein the difference of content of Zr measured by TEM-EDS at the second point location (Zr2) and at any location between said second point location and the center of the particle is around 0.1 at %.
The content of Zr at the second point location (Zr2) is constant: it can be superior to 0 at % and must be inferior or equal to 5.0% of a first content of Zr at the first point location (Zr1). Said second content of Zr2 is equal to a content of Zr at a third point location (Zr3) in said line and said third point is located at any location between the geometric center of said particle and the second point location.
In other words, the thickness of the surface layer corresponds to a minimal distance D defined as:
D (in nm)=Lzr1−LZr2
wherein LZr1 is a first point location at the periphery of a particle, LZr2 is a second point location in a line defined between said first point location and a geometric center of said particle as illustrated in
wherein a second content of Zr measured by TEM-EDS at the second point location LZr2 is superior or equal to 0 at % and inferior or equal to 5.0% of a first content of Zr (Zr1) measured at the first point location. Said second content of Zr (Zr2) is defined as:
Zr2 (in at %)=Zr3±0.1 at %, and optionally
Zr1−Zr2≥10.0 at %
Zr3 is a third content of Zr (in at %) at a third point location (LZr3) in said line, said third point is located at any location between the geometric center of said particle and the second point location LZr2.
When Zr2 and Zr3 are superior to 0.0 at %, the second and third content of Zr corresponds to the content of Zr, measured by TEM-EDS, present as a dopant in the core of the particles according to the invention.
The TEM-EDS protocol is applied as follows:
The aforementioned steps 1) to 4) are repeated as many times as there are particles to be analyzed.
The aforementioned TEM-EDS measurement is performed on at least one particle. When more than one particle is measured, the Zr/(Ni+Mn+Co+Zr) are numerically averaged.
For example, but not limiting to the invention, TEM-EDS measurement is performed with a Tecnai G2 F30 S-TWIN (FEI) with ELITE T 70 detector (EDAX).
As appreciated by the skilled person, for any of the Embodiments 1 to 5, ZrB is expressed as molar fraction, as measured by XPS analysis compared to the sum of molar fractions of Co, Mn, Ni, and Zr, as measured by XPS analysis; in particular ZrB is the molar fractions of Zr measured in a region of a secondary particle of the positive electrode active material according to invention defined between a first point of an external edge of said particle and a second point at a distance from said first point, said distance separating said first to said second point being equal to a penetration depth of said XPS, said penetration depth D being comprised between 1.0 to 10.0 nm. In particular, the penetration depth is the distance along an axis perpendicular to a virtual line tangent to said external edge and passing through said first point.
The external edge of the particle is, in the framework of this invention, the boundary or external limit distinguishing the particle from its external environment.
Therefore, 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”. In the framework of the present invention, at % signifies atomic percentage. The at % or “atomic percent” 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 designation at % is equivalent to mol % or “molar percent”. For example, but not limiting to the invention, XPS analysis is carried out with a Thermo K-α+ spectrometer (Thermo Scientific).
The present invention concerns a use of the positive electrode active material according to any of the preceding Embodiments 1 to 5 in a battery.
The present invention is also inclusive of a process for manufacturing the positive electrode active material according to any of the preceding Embodiments 1 to 5, comprising the steps of:
In a preferred embodiment the lithium transition metal-based compound is a lithium nickel-based oxide compound.
In a preferred embodiment of the method the lithium transition metal-based oxide compound comprising Li, M′ and oxygen, wherein M′ comprises Ni, Mn, Co and D, wherein D is at least one element of the group consisting of: Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, and Zn; preferably Al, B, Cr, Nb, S, Si, Ti, Y, W
Preferably the lithium transition metal oxide powder used is also typically prepared according to a lithiation process, that is the process wherein a mixture of a transition metal precursor and a lithium source is heated at a temperature preferably of at least 500° C. Typically, the transition metal precursor is prepared by coprecipitation of one or more transition metal sources, such as salts, and preferably sulfates of the M′ elements Ni, Mn and/or Co, in the presence of an alkali compound, such as an alkali hydroxide e.g. sodium hydroxide and/or ammonia.
Preferably the method comprises a further step, before heating said mixture, of drying said mixture, preferably by means of vacuum heating.
In a preferred embodiment of the method, the source of Zr is a Zr-alkoxide, preferably Zr-ethoxide, Zr-propoxide or Zr-butoxide, more preferably Zr-propoxide. In a preferred embodiment the Zr-alkoxide is mixed as a solid with the mixture. Alternatively, and more preferably, the Zr alkoxide is mixed as a solution with the slurry, wherein the solution comprises the Zr-alkoxide and a further alcohol, wherein the alkoxide group is a conjugate base of the further alcohol. For example, the Zr-alkoxide is Zr-propoxide, which is dissolved in propanol. Typically, the solution comprises 50-90 wt. % of the Zr-alkoxide by total weight of the solution. Examples of such a solution are a 70 wt. % Zr-propoxide in 1-propanol or a 80 wt. % Zr-butoxide in 1-butanol.
Preferably, the alcohol solvent is methanol, ethanol, propanol or butanol, preferably ethanol.
The present invention is also inclusive of a solid-state battery comprising the positive electrode active material according to any of the preceding Embodiments 1 to 5, preferably the solid-state battery comprises a sulfide based solid electrolyte, more preferably the sulfide based solid electrolyte comprises Li, P and S. Typically, the following sulfur containing compounds of Li6PS5Cl (LPSCL), Thio-LISICON (Li3.25Ge0.25P0.75S4) , Li2S—P2S5—LiCl, LiC2S—SiS2, LiI—Li2S—SiS2, Li—P2S5—LiCl, LiC2S—SiS2, LiI—Li2S—SiS2, LiI—Li2S—P2S5, LiI—Li2SP2O5, LiI—Li3PO4—P2S5, Li2S—P2S5, Li3PS4, Li7P3S11, LiI—Li2S—B2S3, L13PO4—Li2S—SiS2, Li3PO4Li2S—SiS2, LiPO4—Li2S—SiS2, Li10GeP2S12, Li9.54Si1.74P1.44S11.7Cl0.3, and/or Li7P3S11 may be suitably used.
a. SEM image shows secondary particle of CEX2.2 comprising plurality of primary particles. Dotted line shows the area to be captured in order to obtain the average primary particle diameter.
b. SEM image of CEX2.2 to obtain the average primary particle diameter.
c. SEM image of EX1 to obtain the average primary particle diameter.
In the drawings and the following detailed description, preferred embodiments are described so as to enable the practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. The invention includes numerous alternatives, modifications and equivalents that are apparent from consideration of the following detailed description and accompanying drawings.
The amount of Li, Ni, Mn, Co, and Zr in the positive electrode active material powder is measured with the Inductively Coupled Plasma (ICP) method by using an Agilent ICP 720-ES (Agilent Technologies, https://www.agilent.com/cs/library/brochures/5990-6497EN%20720-725_ICP-OES_LR.pdf). 2 grams of powder sample is dissolved into 10 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 glass and heated on a hot plate at 380° C. until complete dissolution of the precursor. After being cooled to room temperature, the solution of the Erlenmeyer flask is poured into a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with deionized water up to the 250 mL mark, followed by complete homogenization. An appropriate amount of solution is taken out by pipette and transferred into a 250 mL volumetric flask for the 2nd dilution, where the volumetric flask is filled with internal standard and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this 50 mL solution is used for ICP measurement.
The morphology of positive electrode active materials is analyzed by a Scanning Electron Microscopy (SEM) technique. The measurement is performed with a JEOL JSM 7100F (https://www.jeolbenelux.com/JEOL-BV-News/jsm-7100f-thermal-field-emission-electron-microscope) under a high vacuum environment of 9.6×10−5 Pa at 25° C.
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.
The diameter of primary particle is calculated by using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA) according to the following steps:
and obtain the average primary particle diameter for at least 50 particles.
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. C1s 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 Version2.3.19PR1.0 (Casa Software, http://www.casaxps.com/) using a Shirley-type background treatment and Scofield sensitivity factors. The fitting parameters are according to Table 1a. 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 Zr and Co peaks, constraints are set for each defined peak according to Table 1b.
For the preparation of a positive electrode, a slurry contains positive electrode active material powder, Li—P—S based solid electrolyte, carbon (Super-P, Timcal), and binder (RC-10, Arkema)—with a formulation of 64.0:30.0:3.0:3.0 by weight—in butyl acetate solvent is mixed in Ar-filled glove box. The slurry is casted on one side of an aluminum foil followed by drying the slurry coated foil in a vacuum oven to obtain a positive electrode. The obtained positive electrode is punched with a diameter of 10 nm wherein the active material loading amount is around 4 mg/cm2.
For the preparation of negative electrode, Li foil (diameter 3 mm, thickness 100 μm) is placed centered on the top of In foil (diameter 10 nm, thickness 100 μm) and pressed to form Li—In alloy negative electrode.
For the preparation of separator which also has a function of the solid electrolyte in a battery, the Li—P—S based solid electrolyte is pelletized with a pressure of 250 MPa to obtain 100 μm pellet thickness.
A sulfide solid-state battery is assembled in an argon-filled glovebox with such order from bottom to top: positive electrode comprising Al current collector with the coated part on the top-separator-negative electrode with Li side on the top-Cu current collector. The stacked components are pressed together with a pressure of 250 MPa and placed in an external cage to prevent air exposure.
The testing method is a conventional “constant cut-off voltage” test. The conventional cell test in the present invention follows the schedule shown in Table 2. Each cell is cycled at 60° C. using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo). The schedule uses a 1 C current definition of 160 mA/g. The initial charge capacity (CQ1) and discharge capacity (DQ1) are measured in constant current mode (CC) at C rate of 0.1 C in below voltage range:
The irreversible capacity IRRQ is expressed in % as follows:
To examine the Zr distributions within a lithium transition metal-based oxide particle, cross-sectional TEM lamellas of particles are prepared by Nova Nano SEM200 (FEI). A Ga ion beam is used with 30 kV voltage and 30 pA-7 nA current. The obtained etched sample has a dimension of 5×8 μm with 100 nm thickness. Using the prepared (etched) sample, the surface property from the top to the center of the lithium transition metal-based oxide particle is analyzed by TEM and energy-dispersive X-ray spectroscopy (EDS). The TEM-EDS line scan is performed on a Tecnai G2 F30 S-TWIN (FEI) with ELITE T 70 detector (EDAX). An EDS analysis of the lithium transition metal-based oxide particle provides the quantitative element analysis of the cross-section. Zr content is normalized by the total atomic fraction of Ni, Mn, Co, and Zr.
The invention is further illustrated by the following (non-limitative) examples:
CEX1 is obtained through a solid-state reaction between a lithium source and a transition metal-based source running as follows:
Optionally, a source of dopant can be added in the co-precipitation process in Step 1) or in the mixing step in the Step 2) together with lithium source. A certain element can be added as a dopant, for instance, to improve the electrochemical properties of the positive electrode active material.
EX1 is obtained through a solid-state reaction between a lithium source and a transition metal-based source running as follows:
CEX2.1 is obtained through the same procedure as CEX1, except that the first heating temperature in Step 3) is 860° C.
CEX2.2 is obtained through the same procedure as EX1, except that the first heating temperature in Step 3) is 860° C.
CEX3 is obtained through the same procedure as CEX1, except that the first heating temperature in Step 3) is 795° C.
EX2 is obtained through the same procedure as EX1, except that the first heating temperature in Step 3) is 795° C.
CEX5 is obtained through the same procedure as CEX1, except that the first heating temperature in Step 3) is 750° C.
EX4 is obtained through the same procedure as EX1, except that the first heating temperature in Step 3) is 750° C.
CEX6 is obtained through the same procedure as CEX1, except that the first heating temperature in Step 3) is 750° C.
EX5 is obtained through the same procedure as EX1, except that the first heating temperature in Step 3) is 750° C.
Table 3 summarizes the primary particle diameter, composition, and the corresponding electrochemical properties of example and comparative examples. The average primary particle diameter of EX1, EX2, EX3 and EX4 are 270, 231, 190, and 192 nm, respectively. These average diameters are smaller than the average primary particle diameters of CEX2.1 and CEX2.2 which are 371 nm. The primary particle SEM images of CEX2.2 and EX1 are shown in
In the Table 3, the XPS analysis result of EX1 and CEX2.2 showing Zr atomic ratio (equivalent with molar ratio) with respect to the total atomic fraction of Ni, Mn, Co, and Zr (ZrB). The table also compares the result with that of ICP. The ZrB higher than 0 indicates said Zr is 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, Zr atomic ratio obtained from ICP measurement (ZrA) is from the entire particles. Therefore, the ratio of XPS to ICP (ZrB/ZrA) higher than 1 indicates said elements Zr presence mostly on the surface of the positive electrode active material. The higher ZrB/ZrA value corresponds with the more Zr presence in the surface of positive electrode active material. ZrB/ZrA in EX1 is higher than that of CEX2.2 ZrB/ZrA. The representative of XPS spectra showing Zr3d5 and 3d3 peaks of CEX2.2 and EX1 are displayed in
Carbon content in positive electrode active material after Zr treatment is higher comparing with before treatment which associated with a better electrochemical performance of active material. Carbon is originated from the Zr alkoxide compound used in the treatment.
The combination of average primary particle diameter in the range of 170 nm to 340 nm and ZrB/ZrA higher than 50.0, preferably higher than 100.0, can achieve the objective of the present invention, which is to provide a positive electrode active material having an improved first charge capacity of at least 160 mAh/g in the solid-state battery.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21159378.5 | Feb 2021 | EP | regional |
| 21159385.0 | Feb 2021 | EP | regional |
| 21159397.5 | Feb 2021 | EP | regional |
| 21159402.3 | Feb 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/054619 | 2/24/2022 | WO |
