Method for preparing precursor materials for Li-containing cathode active materials

Abstract

1. A method for preparing a precursor material for a Li-containing cathode active material for a battery, the method comprising a spray pyrolysis step of decomposing droplets of an aqueous solution in a heated chamber to produce a metal oxide, wherein the metal oxide is either a mixed metal oxide comprising the elements Ni and one or both of the elements Co and Mn, and the aqueous solution is a mixed solution of a salt of Ni and a salt of Co and / or Mn, or the metal oxide is Ni oxide and the aqueous solution is a solution of a salt of Ni, the method comprising a spray drying step of spray drying an aqueous slurry comprising the metal oxide to form the precursor material.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a precursor material for a Li-containing cathode active material, i.e., a positive electrode active material, and to the Li-containing cathode active material from the precursor. [Background technology]

[0002] Generally, Li-containing cathode active materials are prepared by first making precursors of Co and / or Ni and / or Mn and / or Al, and then reacting such precursors with a lithium source in a furnace.

[0003] The precursors are typically single-element inorganic compounds or mixtures of single-element or multi-element inorganic compounds of the elements Co and / or Ni and / or Mn and / or Al, such as oxides, hydroxides, or carbonates. The precursors themselves typically contain no or very little Li.

[0004] A good precursor in an industrial context not only has properties that allow the preparation of a good quality final product, but also needs to be cheap to produce and lend itself to cheap further manufacturing steps.

[0005] It is known to prepare mixed Ni-Co-Mn oxides as precursors for Li-containing cathode active materials using spray pyrolysis from mixed chloride solutions, see Frohlich et al., "New large-scale production route for synthesis of lithium nickel manganese cobalt oxide," J Solid State Electrochem, 21, 3403-3410 (2017).

[0006] From WO 2019 / 185349 it is also known to use spray pyrolysis to prepare mixed Ni-Co-Mn oxides.

[0007] However, such known mixed oxides have drawbacks, in particular, they cause a relatively high Cl content in the final Li-containing cathode active material and, due to their low density, cause a low furnace capacity for the subsequent reaction step with a Li source.

[0008] It is also known to use spray pyrolysis from a mixed nitrate solution containing Li, followed by spray drying, to prepare LiMnO, which can be used as a Li-containing cathode active material. This is disclosed in TANIGUCHI et al., "Synthesis of spherical LiMnO microparticles by a combination of spray pyrolysis and drying method," POWDER.TECHNOLOGY, Vol. 181, No. 3, January 29, 2008, pp. 228-236.

[0009] However, this produces gaseous NO and NO2 as decomposition products. This is undesirable because NO and NO2 are highly polluting gases in the atmosphere, causing both smog and acid rain. Therefore, such methods require very elaborate and expensive removal of NO and NO2 from the gases resulting from the pyrolysis.

[0010] It is also known to use spray pyrolysis from a mixed chloride solution containing Li, followed by spray drying, to prepare lithiated metal oxides that can be used directly as Li-containing cathode active materials. This is disclosed in CN104934572. However, such a method results in a high Cl content in the final product, making it less suitable for use in batteries. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2019 / 185349 [Patent Document 2] Chinese Patent Application Publication No. 104934572 [Non-patent literature]

[0012] [Non-Patent Document 1] Frohlich et al., “New large-scale production route for synthesis of lithium nickel manganese cobalt oxide”, J Solid State Electrochem, 21, 3403–3410 (2017) [Non-patent document 2] TANIGUCHI et al., "Synthesis of spherical LiMn2O4 microparticles by a combination of spray pyrolysis and drying method," POWDER TECHNOLOGY, Vol. 181, No. 3, January 29, 2008, pp. 228-236 Summary of the Invention [Means for solving the problem]

[0013] The present invention is directed to avoiding and / or reducing these and other disadvantages and accordingly provides a method for preparing a precursor material for a Li-containing cathode active material for a battery, the method comprising a spray pyrolysis step in which droplets of an aqueous solution are decomposed in a heated chamber to produce a metal oxide, the method comprising a spray drying step in which an aqueous slurry comprising the metal oxide is spray-dried, either directly from the spray pyrolysis step or after one or more intermediate processing steps, to form a precursor material, the metal oxide having the following characteristics: 1) The metal oxide is a mixed metal oxide containing element Ni and one or both of elements Co and Mn, and the aqueous solution is a mixed solution of a salt of Ni and a salt of Co and / or Mn; 2) The metal oxide is Ni oxide, and the aqueous solution is a solution of Ni salt; 3) the metal oxide is Mn oxide and the aqueous solution is a solution of a salt of Mn.

[0014] In chemistry, a mixed oxide is the name for an oxide compound that contains cations of two or more chemical elements or cations of a single element in several oxidation states.

[0015] The first option in this definition is intended herein.

[0016] Alternatively, a mixed metal oxide may be defined as a metal oxide in which each particle of the metal oxide contains all of the metal elements present in the metal oxide.

[0017] As mixed metal oxides, only oxide compounds containing cations of two or more different metal elements are considered, as opposed to mixtures of single metal oxides.

[0018] A mixed salt solution refers to a solution in which salts of different metal elements are present in the same solvent, whether or not an explicit mixing step has taken place.

[0019] Various embodiments according to the present invention are disclosed in the claims and in this specification. The embodiments and examples described in the claims and this specification can be freely combined with each other unless expressly stated otherwise. Throughout this specification, when any numerical range is provided, the range also includes the endpoints unless expressly stated otherwise.

[0020] The present invention relates to the following preferred embodiments.

[0021] The spray drying process significantly increases the bulk density of the metal oxides, thereby improving the capacity of the furnace used to react the precursor material with Li.

[0022] In a preferred variant, the salt or salts are chlorides, which are cheaply available, highly soluble, and can be easily recycled.

[0023] In a preferred variant, the method includes a slurry preparation step in which the metal oxide particles, either directly from the spray pyrolysis step or after one or more intermediate processing steps, are mixed with water to prepare an aqueous slurry.

[0024] In a preferred variant, the method includes a washing step in which a mixture of metal oxide and water is prepared, either directly from the spray pyrolysis step or after one or more intermediate processing steps, in a ratio (weight of water) / (weight of metal oxide) of at least 0.1, preferably at least 0.5, and this mixture is filtered, centrifuged or decanted to recover the metal oxide, whereby the washing step precedes the slurry preparation step.

[0025] In this washing step, residual anions in the metal oxide, especially chloride, can be removed since they are soluble in water. Those skilled in the art will understand that the amount of water used will depend on the anion content desired after the washing step.

[0026] In a preferred variant, the method includes a size reduction step in which the metal oxide undergoes particle size reduction, either directly from the spray pyrolysis step or after one or more intermediate processing steps, the size reduction step being carried out before the spray drying step.

[0027] This improves the homogeneity of the precursor material produced and also allows for increased capacity of the spray drying process.

[0028] In a preferred variant, the size reduction step is carried out on the metal oxide wetted with water. If there is a preceding wet step, such as the washing step mentioned above, this avoids intermediate drying of the metal oxide. It also reduces dust generation.

[0029] In a preferred variant, the median particle size D50 of the metal oxide particles in the aqueous slurry is between 10 nm and 1000 nm, so that the metal oxide content obtainable in the aqueous slurry may be optimal.

[0030] In a preferred variation, the precursor material comprises spherical particles and the precursor material has a density of at least 1.0 g / cm 3 , preferably at least 1.3 g / cm 3 , more preferably at least 1.4 g / cm 3 Spherical particles have a bulk density of at least 0.5 when viewed in cross section under a microscope. This is calculated as the ratio between the area of ​​the particle and the area of ​​the disk with the largest diameter of the particle.

[0031] The spherical particles preferably have a median particle size D50 of at least 2 μm and at most 50 μm to provide a good balance between ease of handling and rate of reaction with Li in subsequent processing steps.

[0032] The metal oxide preferably has a molar content of Mn of y, a molar content of Co of z, a molar content of Ni of b, and a molar content of A of a, where A is any metal element other than Li, Ni, Mn, and Co; 0.20≦b / (y+z+b+a)≦1.00, for example, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or 0.90; 0≦y / (y+z+b+a)≦0.80, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, or 0.70; 0≦z / (y+z+b+a)≦0.60, for example, 0.10, 0.20, 0.30, 0.40, or 0.50; and 0≦a / (y+z+b+a)≦0.10, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, or 0.09.

[0033] More preferably, 0.30≦b / (y+z+b+a)≦1.00, and even more preferably, 0.45≦b / (y+z+b+a)≦1.00.

[0034] More preferably, the metal oxide is a mixed metal oxide, and 0.30≦b / (y+z+b+a)≦0.95 and 0.04≦z / (y+z+b+a)≦0.60, and even more preferably 0.45≦b / (y+z+b+a)≦0.90 and 0.04≦z / (y+z+b+a)≦0.35. [Brief explanation of the drawings]

[0035] [Figure 1] This is a CS-SEM image of EX1.2. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following detailed description describes preferred embodiments in order to enable the practice of the invention. While the invention is described with reference to these particular 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 will be apparent from consideration of the following detailed description and the accompanying drawings.

[0037] A) CS-SEM (cross-sectional scanning electron microscope) analysis Cross sections of the transition metal oxide precursors described herein, i.e., precursor materials, are prepared by an ion beam cross section polishing (CP) instrument, JEOL (IB-0920CP), which uses argon gas as the beam source.

[0038] To prepare the test specimens, a small amount of transition metal oxide precursor powder was mixed with the resin and hardener, and the mixture was then heated on a hot plate for 10 minutes. After heating, it was placed in the ion beam cutting instrument and the settings were adjusted to the standard procedure of a voltage of 6.5 kV for a duration of 3 hours.

[0039] The morphology of the transition metal oxide precursors was analyzed by scanning electron microscopy (SEM). Measurements were performed using a JEOL JSM 7100F (https: / / www.jeolbenelux.com / JEOL-BV-News / jsm-7100f-thermal-field-emission-electron-microscope) at 25 °C with a resolution of 9.6 × 10 -5 The experiment was carried out under a high vacuum environment of 100 Pa.

[0040] B) Particle size analysis The particle size distribution (PSD) of the transition metal oxide precursor powders, i.e., precursor materials, was measured by laser diffraction particle size analysis using a Malvern Mastersizer 3000 equipped with a Hydro MV wet dispersion accessory (https: / / www.malvernpanalytical.com / en / products / product-range / mastersizer-range / mastersizer-3000#overview) after dispersing each powder sample in aqueous media. Sufficient sonication and stirring were applied, and appropriate surfactants were introduced, to improve powder dispersion. The median particle size D50 is defined as the particle size at 50% of the cumulative volume percent distribution obtained from the Malvern Mastersizer 3000 measurement using Hydro MV.

[0041] C) Bulk density The bulk density of the precursor material powder is determined by measuring the mass of the powder in a measuring cylinder having a specific volume. The precursor bulk density is calculated according to the following formula:

[0042]

number

[0043] D) Carbon analyzer The carbon content of the positive electrode active material powder is measured using an Emia-Expert carbon / sulfur analyzer manufactured by Horiba, Ltd. 1 g of the example or comparative example is placed in a ceramic crucible in a high-frequency induction furnace. 1.5 g of tungsten and 0.3 g of tin as promoters are added to the crucible. The powder is heated at a programmable temperature, during which the gases produced during combustion are then analyzed by an infrared detector. The carbon concentration is determined by CO2 and CO2 analysis.

[0044] E) ICP analysis The amounts of metal elements, such as Ni, Mn, and Co, in the precursor were measured by inductively coupled plasma (ICP) using an Agilent ICP720-ES (Agilent Technologies). Two grams of powder sample were dissolved in 10 mL of high-purity hydrochloric acid (at least 37 wt.% HCl based on the total weight of the solution) in an Erlenmeyer flask. The flask was covered with glass and heated on a hot plate at 380 °C until the precursor was completely dissolved. After cooling to room temperature, the solution in the Erlenmeyer flask was poured into a 250 mL volumetric flask. The volumetric flask was then filled to the 250 mL mark with deionized water, followed by thorough homogenization. An appropriate amount of the solution was removed with a pipette and transferred to a 250 mL volumetric flask for the second dilution. The volumetric flask was then filled to the 250 mL mark with internal standard and 10% hydrochloric acid, followed by homogenization. Finally, this 50 mL solution was used for ICP measurement.

[0045] The invention is further illustrated by the following (non-limiting) examples.

[0046] Example 1.1: Mixed Metal Oxides The precursor product was obtained by a spray pyrolysis and spray drying process carried out as follows. 1) Preparation of Feed Solution: A mixed feed solution was prepared containing NiCl, MnCl, and CoCl solutions in water at a total concentration of 110 grams / L with Ni:Mn:Co ratio of 0.6:0.2:0.2. 2) Spray pyrolysis: The feed solution was sprayed in droplet form into a heated chamber at 650 °C to decompose the salts and form mixed metal oxide powders. The chamber volume was approximately 8.8 m 3 and the feed rate was 30 L / hour. 3) Washing: The mixed metal oxide powder was washed with water (25 wt% solids) followed by filtration to reduce the chloride content. 4) Slurry formulation: A slurry was prepared by mixing the washed product from step 3) with a dispersant (Dolapix CA, Zschimmer & Schwarz, DE) to have 70 wt. % solids and 2 wt. % dispersant in water. 5) Wet bead mill: The prepared slurry was wet bead milled at a specific milling energy of 1300 kWh / T. The milling media was Y-stabilized ZrO2 beads (YSZ) with a diameter of 1 mm. The D50 of the milled particles was 0.28 μm. 6) Spray drying: The milled slurry was spray dried through a two fluid nozzle with an inlet temperature of 170° C. and an outlet temperature of 100° C. The product of this step was a precursor powder labeled EX1.1.

[0047] EX1.1 powder has a weight of 1.8g / cm based on the total weight of the powder. 3 and a carbon content of 0.7% by weight.

[0048] The intermediate product after step 2 is 0.31 g / cm 3 The bulk density was 1000 .mu.m.

[0049] Example 1.2: Heated Mixed Metal Oxides EX1.1 was heated in an oxygen atmosphere in a furnace at 500 °C for 5 hours to produce EX1.2 powder with a D50 of 12.6 μm. A CS-SEM image of the EX1.2 particles is shown in Figure 1. The carbon content was 0.012 wt% based on the total weight of EX1.2.

[0050] Example 1.3: Mixed Metal-Containing Cathode Active Material EX1.3 was obtained by solid-state reaction between a lithium source and a transition metal-based precursor, which was carried out as follows. 1) Mixing: The precursor powder EX1.2 and LiOH as a lithium source were homogeneously mixed in an industrial blending device with a lithium to metal Me (Li / Me) ratio of 1.05 to obtain a mixture (Me = Ni, Mn, Co). 2) Heating: The mixture from step 1) was heated at 840° C. for 15 hours under an oxygen atmosphere. The heated powder was crushed, classified and sieved to obtain the lithiated product labeled EX1.3.

[0051] Example 2.1: Nickel Oxide EX2.1 was prepared according to the same method as EX1.1, except that the feed solution in step 1) only contained NiCl2. The D50 of the ground particles was 0.25 μm. EX2.1 was prepared at 1.5 g / cm 3 The NiO precursor powder has a bulk density of

[0052] Example 2.2: Heated Nickel Oxide EX2.1 was heated in a furnace at 500°C for 5 hours under an oxygen atmosphere to produce EX2.2 powder with a D50 of 12.0 μm. The carbon content was 0.015 wt% based on the total weight of EX2.2.

[0053] Example 2.3: Nickel-containing positive electrode active material EX2.3 was obtained by solid-state reaction between a lithium source and a transition metal-based precursor, carried out as follows. 1) Mixing: Precursor powder EX2.2 and LiOH as a lithium source are homogeneously mixed in an industrial blending device with a lithium to metal Me (Li / Me) ratio of 1.05 to obtain a mixture (Me=Ni, Mn, Co). 2) Heating: The mixture from step 1) was heated at 750° C. for 15 hours under an oxygen atmosphere. The heated powder was crushed, classified and sieved to obtain the lithiated product labeled EX2.3.

Claims

1. 1. A method for preparing a precursor material for a Li-containing cathode active material for a battery, comprising: a spray pyrolysis step in which droplets of an aqueous solution are decomposed in a heated chamber to produce metal oxides; The metal oxide is a mixed metal oxide containing Ni and one or both of Co and Mn, and the aqueous solution is a mixed solution of a Ni salt and a Co and / or Mn salt. Or the metal oxide is Ni oxide, and the aqueous solution is a solution of a Ni salt. or the metal oxide is a manganese oxide, and the aqueous solution is a solution of a manganese salt; the method includes a drying step of drying the aqueous slurry comprising the metal oxide to form the precursor material; The method, wherein the drying step is a spray drying step in which the aqueous slurry is spray dried to form the precursor material.

2. 2. The method of claim 1, wherein the metal oxide is a mixed metal oxide containing the element Ni and one or both of the elements Co and Mn, and the aqueous solution is a mixed solution of a salt of Ni and a salt of Co and / or Mn.

3. 2. The method of claim 1, wherein the salt is a chloride or the salts are chlorides.

4. 10. The method of claim 1, wherein the precursor material is heated at a temperature of at least 300°C and at most 1000°C to produce a heat-treated precursor material.

5. 10. The method of claim 1, wherein the method includes a washing step in which a mixture of the metal oxide and water is prepared in a ratio (weight of water) / (weight of metal oxide) of at least 0.1, and the mixture is filtered, centrifuged, or decanted to recover the metal oxide, whereby the washing step occurs before the slurry preparation step.

6. 10. The method of claim 1, wherein the method comprises a size reduction step in which the metal oxide undergoes particle size reduction, the size reduction step occurring before the spray drying step.

7. 7. The method of claim 6, wherein the size reduction step is performed on a water-wet metal oxide.

8. 10. The method of claim 1, wherein the concentration of said metal oxide in said aqueous slurry is at least 30% by weight.

9. 2. The method of claim 1, wherein the metal oxide particles in the aqueous slurry have a first particle size distribution as determined by laser diffraction with a median particle size D50 of at most 0.60 μm.

10. The precursor material comprises spherical particles, and the precursor material is concentrated at a concentration of at least 1.0 g / cm ３ 2. The method of claim 1, wherein the bulk density is

11. 11. The method of claim 10, wherein the spherical particles have a second particle size distribution determined by laser diffraction, the second particle size distribution having a second D50 of at least 2 μm.

12. 11. The method of claim 10, wherein the spherical particles have a second particle size distribution determined by laser diffraction, the second particle size distribution having a second D50 of at most 25 μm.

13. the metal oxide has a molar Mn content y, a molar Co content z, a molar Ni content b, and a molar A content a, wherein A is any metal element other than Li, Ni, Mn, and Co; 0.20≦b / (y+z+b+a)≦1.00, 0≦y / (y+z+b+a)≦0.80, 0≦z / (y+z+b+a)≦0.60, and 2. The method of claim 1, wherein 0≦a / (y+z+b+a)≦0.

10.

14. 2. The method of claim 1, wherein the metal oxide has a molar Mn content y, a molar Co content z, a molar Ni content b, and a molar A content a, where A is any metal element other than Li, Ni, Mn, and Co, and 0.30≦b / (y+z+b+a)≦0.95 and 0.05≦(y+z+a) / (y+z+b+a)≦0.70.

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