Lithium hydroxide-based powder for preparing lithium complex oxide, composition comprising lithium hydroxide-based powder and transition metal hydroxide or

Abstract

The present invention relates to a lithium hydroxide-based powder for preparing a lithium composite oxide, in which the lithium hydroxide-based powder has a span of at most 5.0, the span is defined as (D90-D10) / D50, and D10, D50 and D90 are defined as particle sizes at 10%, 50% and 90% of the cumulative volume% distribution, respectively, when measured by a laser scattering method.

Description

Technical Field and Background

[0001] The present invention relates to a lithium hydroxide-based powder for preparing a lithium composite oxide. More specifically, the present invention relates to a lithium hydroxide-based powder for preparing a lithium composite oxide, wherein the electrochemical properties, such as capacity fade, of a lithium-ion battery containing the lithium composite oxide are enhanced due to the lithium hydroxide-based powder. The present invention also relates to a composition comprising the lithium hydroxide-based powder and a transition metal hydroxide or oxyhydroxide, i.e., a precursor. The present invention also relates to a method for producing the lithium hydroxide-based powder.

[0002] The lithium composite oxide has been used as a positive electrode active material for lithium-ion batteries. The lithium composite oxide is synthesized by mixing the precursor and the lithium hydroxide-based powder to obtain a mixture and then heating the mixture to allow a reaction between the lithium hydroxide-based powder and the precursor. In order to design a lithium-ion battery with enhanced electrochemical properties, it is necessary to confirm not only the effect of the precursor on the electrochemical properties of the lithium-ion battery, but also the effect of the lithium hydroxide-based powder on the electrochemical properties of the lithium-ion battery. In other words, there is a need for a lithium hydroxide-based powder that can enhance the electrochemical properties of lithium-ion batteries.

[0003] A first object of the present invention is to provide a lithium hydroxide-based powder for preparing a lithium composite oxide, which enhances the electrochemical properties of a lithium ion battery including the lithium composite oxide.

[0004] A second object of the present invention is to provide a composition comprising the lithium hydroxide-based powder and a transition metal hydroxide or oxyhydroxide.

[0005] A third object of the present invention is to provide a method for producing the above-mentioned lithium hydroxide-based powder. Summary of the Invention

[0006] The first object of the present invention is achieved by providing a lithium hydroxide-based powder for preparing a lithium composite oxide, wherein the lithium hydroxide-based powder has a span of at most 5.0, the span being defined as (D90-D10) / D50, and D10, D50 and D90 being defined as the particle sizes at 10%, 50% and 90% of the cumulative volume % distribution, respectively, when measured by a laser scattering method.

[0007] The second object of the present invention is achieved by providing a composition comprising the above-mentioned lithium hydroxide-based powder and a transition metal hydroxide or oxyhydroxide comprising M', wherein M' comprises:

[0008] -Ni with content x, where x ≥ 30.0 at% relative to M';

[0009] - Co content y, where 0.0 ≤ y ≤ 60.0 at% relative to M';

[0010] - Mn in an amount z, where 0.0 ≤ z ≤ 80.0 at% relative to M'; and

[0011] - a content a of D, wherein 0.0 ≤ a ≤ 5.0 at % relative to M', wherein D is at least one element selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr,

[0012] where x+y+z+a is 100.0 at%.

[0013] The third object of the present invention is achieved by providing a method for producing the above-mentioned lithium hydroxide-based powder, the method comprising:

[0014] - drying the lithium-containing compound in a vacuum oven or in an oven under an atmosphere free of carbon dioxide to form a dried lithium-containing compound; and

[0015] - pulverizing the dried lithium-containing compound in a pulverizer, wherein the pulverizer is under a carbon dioxide-free atmosphere and a dry air atmosphere. DETAILED DESCRIPTION

[0016] In the following detailed description, preferred embodiments are described in detail to enable the practice of the present invention. Although the present invention has been described with reference to these specific preferred embodiments, it should be understood that the present invention is not limited to these preferred embodiments. On the contrary, the present invention encompasses numerous alternatives, modifications, and equivalents, as will become apparent from consideration of the following detailed description.

[0017] Lithium hydroxide based powder

[0018] In a first aspect, the present invention relates to a lithium source material for preparing a lithium composite oxide, wherein the lithium source material has a span of at most 5.0, wherein the lithium source material comprises lithium hydroxide, and wherein the span is defined as (D90-D10) / D50, and D10, D50, and D90 are defined as the particle sizes at 10%, 50%, and 90% of the cumulative volume % distribution, respectively, when measured by a laser scattering method. Since the lithium source material comprises lithium hydroxide, the lithium source material can be referred to as a lithium hydroxide-based powder.

[0019] The present inventors have discovered that the electrochemical properties of lithium-ion batteries, such as capacity fading, are improved by using a lithium source material whose span is adjusted to at most 5.0. Specifically, if a lithium composite oxide is prepared using a lithium source material whose span exceeds 5.0, the crystals of the lithium composite oxide will grow excessively, the particle size distribution of the lithium composite oxide will become broad, causing agglomeration of fine particles of the lithium composite oxide, and thus, the capacity fading of the lithium-ion battery containing the lithium composite oxide will deteriorate.

[0020] In a preferred embodiment, the lithium source material comprises lithium carbonate in an amount of up to 2% by weight relative to the weight of the lithium source material. In detail, if the amount of lithium carbonate relative to the weight of the lithium source material exceeds 2% by weight, the crystal growth of the lithium composite oxide comprising the lithium source material will be excessively suppressed, and therefore, the capacity decay of the lithium ion battery comprising the lithium composite oxide will become deteriorated. However, even if the amount of lithium carbonate relative to the weight of the lithium source material does not exceed 2% by weight, if the span of the lithium source material exceeds 5.0, the capacity decay of the lithium ion battery comprising the lithium composite oxide may not have the desired value. Therefore, it is preferred to control the amount of lithium carbonate to at most 2% by weight relative to the weight of the lithium source material, while also controlling the span of the lithium source material to at most 5.0.

[0021] In a preferred embodiment, the content of lithium carbonate is at most 1.5 wt%, preferably at most 0.8 wt%, more preferably at most 0.5 wt%, most preferably 0.3 wt%, relative to the weight of the lithium source material.

[0022] In a preferred embodiment, the span is at most 4.0, preferably at most 3.5, more preferably at most 2.5, most preferably at most 1.5.

[0023] In a preferred embodiment, the content of lithium hydroxide is at least 98.0 wt%, preferably at least 98.5 wt%, more preferably at least 98.2 wt%, most preferably at least 99.0 wt%, relative to the weight of the lithium source material.

[0024] In a preferred embodiment, D50 is at least 1 μm and at most 30 μm, preferably at least 5 μm and at most 20 μm, more preferably at least 7 μm and at most 18 μm, and most preferably at least 10 μm and at most 16 μm. If the D50 of the lithium source material exceeds 30 μm, the reactivity between the lithium source material and the precursor will be reduced. If the D50 of the lithium source material is less than 1 μm, the lithium source material will not be easy to handle because its fluidity is excessively reduced.

[0025] Composition

[0026] In a second aspect, the present invention relates to a composition comprising a lithium source material according to the first aspect and a transition metal hydroxide or oxyhydroxide comprising M', wherein M' comprises:

[0027] -Ni with content x, where x ≥ 30.0 at% relative to M';

[0028] - Co content y, where 0.0 ≤ y ≤ 60.0 at% relative to M';

[0029] - Mn in an amount z, where 0.0 ≤ z ≤ 80.0 at% relative to M'; and

[0030] - a content a of D, wherein 0.0 ≤ a ≤ 5.0 at % relative to M', wherein D is at least one element selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr,

[0031] where x+y+z+a is 100.0 at%.

[0032] In a preferred embodiment, the lithium source material is mixed with a transition metal hydroxide or oxyhydroxide, with the ratio of lithium to transition metal being in the range of 0.98 to 1.02, and the mixture is heated to obtain a lithium composite oxide for a positive electrode active material.

[0033] Within the framework of the present invention, at% means atomic percentage. The at% or "atomic percent" of a given element refers to the percentage of atoms of that element to all atoms in the claimed composition. ICP-OES provides the weight percentage (wt%) of each element contained in the material whose composition is determined by this technique. The conversion from wt% to at% is as follows:

[0034] The at% of the first element E1 in the material (E at1 ) can be obtained from a given wt% of the first element E1 in the material (E wt1 ) conversion,

[0035] ,

[0036] Among them E aw1 is the standard atomic weight of the first element E1, E wti is the i-th element E i wt%,E awi is the i-th element E i The standard atomic weight of , and n is an integer representing the number of types of all elements contained in the material.

[0037] Method for producing lithium hydroxide-based powders

[0038] In a third aspect, the present invention relates to a method for producing a lithium source material according to the first aspect, comprising:

[0039] - drying the lithium-containing compound in a vacuum oven or in an oven under an atmosphere free of carbon dioxide to form a dried lithium-containing compound; and

[0040] - pulverizing the dried lithium-containing compound in a pulverizer, wherein the pulverizer is under a carbon dioxide-free atmosphere and a dry air atmosphere.

[0041] The drying step is performed to reduce the moisture content in the lithium source material, as water molecules inhibit the reaction of lithium in the lithium source material with the precursor. Furthermore, the drying step is performed in a vacuum oven or an oven in an atmosphere free of carbon dioxide, so that the lithium in the lithium source material does not absorb carbon to form lithium carbonate during the drying step.

[0042] In a preferred embodiment, the drying step is carried out at a temperature of at least 70° C., preferably at least 100° C., more preferably at least 150° C., most preferably at least 170° C. and at a temperature of at most 300° C., preferably at most 280° C., more preferably at most 240° C., most preferably at most 210° C. Drying is carried out for at least 30 minutes, preferably at least 40 minutes, more preferably at least 50 minutes and at most 90 minutes, preferably at most 80 minutes, more preferably at most 70 minutes.

[0043] The comminution step is the process of applying mechanical energy to reduce the dried lithium-containing compound. Comminution is preferably dry milling, wherein the dried lithium-containing compound is comminuted in its dry state, ie in the absence of a liquid medium.

[0044] In a preferred embodiment, the pulverizer is a jet mill that reduces particle size by using a jet of compressed gas to impact the particles into each other or into the wall of the jet mill, thereby crushing the particles. The span of the lithium source material according to the first aspect can be controlled to be at most 5.0 by using a jet mill. In addition, in a preferred embodiment, the gas containing no carbon dioxide is injected into the jet mill as a compressed gas so that the lithium in the lithium source material does not absorb carbon and generates lithium carbonate. In addition, the volume flow rate of the gas containing no carbon dioxide is preferably between 0.1 and 20.0 m / s. 3 / min, more preferably 1 to 15m 3 / min range; grinding pressure is preferably in the range of 1 to 10 bar, more preferably in the range of 3 to 7 bar; the feed rate of the dried lithium-containing compound is preferably in the range of 20 to 60 kg / h, more preferably in the range of 30 to 50 kg / h.

[0045] In a preferred embodiment, the carbon dioxide-free gas during at least one of the drying step and the comminuting step is nitrogen.

[0046] In a preferred embodiment, the drying air in the pulverizer has a relative humidity of at most 1%.

[0047] As will be understood by those skilled in the art, all embodiments relating to the positive electrode active material according to the first aspect may be applied to the second and third aspects with appropriate modifications.

[0048] Experimental tests used in the examples

[0049] The following analytical methods were used in the examples:

[0050] A) Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES)

[0051] The elemental contents of the positive electrode active material examples and comparative examples described below were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES) using an Agillent ICP 720-OES. One gram of powder sample was dissolved in 50 mL of high-purity hydrochloric acid in an Erlenmeyer flask. The flask was covered with a watch glass and heated on a hot plate at 380°C until the sample was completely dissolved. After cooling to room temperature, the solution and rinse water from the Erlenmeyer flask were transferred to a 250 mL volumetric flask. The flask was then filled to the 250 mL mark with DI water and thoroughly homogenized. An appropriate amount of the solution was pipetted and transferred to a 250 mL volumetric flask for a second dilution. The flask was then filled to the 250 mL mark with an internal standard and 10% hydrochloric acid and homogenized. Finally, this solution was used for ICP-OES measurement. The Ni, Mn, Co, and Si contents are expressed as weight percent of the sum of these contents. Another suitable solvent can be used to completely dissolve the positive electrode active material powder sample.

[0052] B) Particle size distribution

[0053] Particle size distribution was measured using a Malvern Mastersizer 3000 with a Hydro MV wet dispersion accessory after dispersing examples of positive electrode active material powders as described herein below in an aqueous medium. To improve the dispersion of the positive electrode active material powder examples, sufficient ultrasonic irradiation and stirring were applied, and an appropriate surfactant was introduced. The percentile values ​​D10, D50, and D90 are the particle diameter values ​​at the 10th, 50th, and 90th percentiles of the cumulative distribution, respectively. The span value for hydroxides is (D90-D10) / D50.

[0054] C) Carbon Analysis

[0055] The carbon content of the positive electrode active material powder was measured using a Horiba Emia-Expert carbon / sulfur analyzer. One gram of the positive electrode active material powder was placed in a ceramic crucible in a high-frequency induction furnace. 1.5 grams of tungsten and 0.2 grams of tin were added to the crucible as promoters. The powder was heated at a programmable temperature, and the gases produced during combustion were then analyzed by an infrared detector. The carbon concentration was determined by analyzing CO2 and CO.

[0056] D) Surface Alkali Analysis

[0057] When measuring soluble base content by pH titration, two steps are performed: (a) solution preparation and (b) pH titration. Detailed descriptions of each step are as follows:

[0058] Step (a): Solution Preparation: The powder was immersed in deionized water and stirred in a sealed glass flask containing 100 mL of deionized water for 10 minutes. The amount of positive electrode active material powder was 4 g. After stirring, the powder suspension in water was filtered to dissolve the base, resulting in a clear solution.

[0059] Step (b): pH titration: 90 mL of the clear solution prepared in step (a) was titrated with 0.1 M HCl. The flow rate was 0.5 mL / min, and the pH value was recorded every 3 seconds. The pH titration curve (pH as a function of added HCl) showed two distinct equivalence (or inflection) points. The first equivalence point (corresponding to the amount of HCl in EP1) at around pH 7.4 was determined by OH. - and CO3 2- With H + The second equivalence point at around pH 4.7 (corresponding to the amount of HCl in EP2) is produced by HCO3 - With H + It is speculated that the base dissolved in deionized water is LiOH (amount is ) or Li2CO3 (amount is The values ​​obtained for LiOH and Li2CO3 are the result of surface reaction with deionized water.

[0060] E) Button battery test

[0061] E1) Button Cell Preparation

[0062] To prepare the positive electrode, a slurry containing a 96.5:1.5:2.0 weight ratio of positive electrode active material powder, a conductor (Super P, Timcal), and a binder (KF#9305, Kureha) in a solvent (NMP, Mitsubishi) was prepared using a high-speed homogenizer. The homogenized slurry was spread onto one side of aluminum foil using a knife coater with a 170 μm gap. The slurry-coated foil was dried in an oven at 120°C and then pressed using a calendaring tool. It was then dried again in a vacuum oven to completely remove any remaining solvent from the electrode film. Coin cells were assembled in an argon-filled glove box. A separator (Celgard 2320) was positioned between the positive electrode and a piece of lithium foil serving as the negative electrode. A 1 M solution of LiPF6 in EC / DMC (1:2) was used as the electrolyte and dripped between the separator and the electrodes. The coin cell was then completely sealed to prevent electrolyte leakage.

[0063] E2) Test Method

[0064] The test method was a conventional "constant cut-off voltage" test. Conventional coin cell testing in the present invention followed the protocol shown in Table 1. Each cell was cycled at 25°C using a Toscat-3100 computer-controlled constant current cycling station (from Toyo).

[0065] The scheme was defined using a 1C current of 220 mA / g within the 4.3 V to 3.0 V / Li metal window. The capacity fade rate (QF) was obtained according to the following formula.

[0066]

[0067] Wherein DQ1 is the discharge capacity at the first cycle, DQ7 is the discharge capacity at the 7th cycle, and DQ34 is the discharge capacity at the 34th cycle.

[0068] Table 1. Cycling protocol for coin cell battery testing

[0069]

[0070] Examples

[0071] The present invention is further illustrated in the following examples:

[0072] Example 1

[0073] Lithium hydroxide based powder EX1 was prepared according to the following conditions:

[0074] 1. Drying: Dry the lithium raw material LiOH.H2O (LiOH = 57 wt%, D50 > 250 μm, span > 1.3) in a paddle dryer with a CO2-free air stream with a relative humidity < 1% (dry air). The drying temperature is 180-200°C and the drying time is approximately 1 hour. The jet air flow rate is 15 m 3 / h or so.

[0075] 2. Milling: The dried material from step 1) was milled in a fluidized jet mill using dry air at a milling pressure of 3-6 bar. Milling was continued until the target D50 was reached. The resulting lithium hydroxide-based powder, EX1, had a D50 of approximately 11.3 μm and a span of approximately 2.85.

[0076] The positive electrode active material EX1-C is prepared by a solid-state reaction between a lithium source EX1 and a precursor according to the following steps:

[0077] 1. Co-precipitation: Ni-manganese-cobalt sulphate was prepared by co-precipitation in a large-scale continuous stirred tank reactor (CSTR) with mixed nickel-manganese-cobalt sulphate, sodium hydroxide and ammonia. 0.80 Mn 0.10 Co 0.10 The metal composition of the transition metal oxide hydroxide precursor.

[0078] 2. Mixing: The precursor prepared from step 1) was mixed with EX1 as a LiOH source in an industrial blender to obtain a mixture having a lithium to metal ratio of 1.00.

[0079] 3. Heat treatment: The mixture from step 2) was heated at 830° C. for 8 hours under an oxygen atmosphere, followed by sieving and grinding to obtain EX1-C.

[0080] Comparative Example 1

[0081] CEX1 was prepared using the same method as EX1, except that milling was performed using raw air containing ambient moisture and carbon dioxide in step 2). The resulting lithium hydroxide-based powder CEX1 had a D50 of approximately 11.4 μm and a span of approximately 2.67 μm.

[0082] CEX1-C was prepared according to the same method as EX1-C, except that CEX1 was used as the Li source in step 2).

[0083] Comparative Example 2

[0084] CEX2 was prepared using the same method as EX1, except that a colloid mill with a grinder diameter of 150 mm was used in step 2). The milling speed was 3000 rpm at a 10 μm gap, and the milling time was 20 minutes, performed under a dry air atmosphere. The resulting lithium hydroxide-based powder, CEX1, had a D50 of approximately 29.6 μm and a span of approximately 5.09.

[0085] CEX2-C was prepared according to the same method as EX1-C, except that CEX2 was used as the Li source in step 2.

[0086] Comparative Example 3

[0087] CEX3 was prepared using the same method as CEX2, except that an air atmosphere was used for milling in step 1) and a pin mill was used in step 2). The pin mill speed was 7000 rpm, the feed rate was 10 kg / hour, and milling was performed in a raw air atmosphere for approximately 1 hour.

[0088] CEX3-C was prepared according to the same method as EX1-C, except that CEX3 was used as the Li source in step 2.

[0089] result

[0090] Table 2. Summary of properties of EX1 to CEX3.

[0091]

[0092] Table 3. Summary of properties of positive electrode active materials EX1-C to CEX3-C

[0093]

[0094] Table 2 summarizes the properties of lithium hydroxide-based powders according to the examples and comparative examples. EX1 was dried in a vacuum and jet-milled using dry air. Such processing conditions enabled the lithium hydroxide-based powder of EX1 to have a span of approximately 2.8 while maintaining the Li2CO3 content below 0.6 wt%. When the lithium hydroxide-based powder was obtained from jet milling using virgin air, as in CEX1, the Li2CO3 content was higher than 2 wt% due to the absorption of CO2 during milling. CEX2 was prepared by low-energy milling such as a colloid mill and was observed to have a large D50 and a wider span compared to EX1. As for CEX3, both drying and low-energy milling such as a spiked disc mill were performed under a virgin air atmosphere, resulting in a lithium hydroxide-based powder of CEX3 having a high Li2CO3 content, a large D50, and a wider span compared to EX1.

[0095] Table 3 summarizes the properties of the positive electrode active materials obtained from the lithiation process using lithium hydroxide-based powders according to EX1 to CEX3. It is observed that EX1-C has the lowest levels of carbon and lithium surface impurities compared to the comparative example, as indicated by the Li2CO3 and LiOH contents. Furthermore, EX1-C exhibits the lowest capacity fade rate, QF, which is significantly lower than that of the comparative example. It can be concluded that the lithium hydroxide-based powders prepared according to the present invention are suitable for preparing positive electrode active materials with low Li2CO3 content, low carbon content, and low capacity fade.

Claims

1. A lithium hydroxide-based powder for preparing a lithium composite oxide, wherein the lithium hydroxide-based powder has a span of at most 5.0, The span is defined as (D90-D10) / D50, and D10, D50 and D90 are defined as the particle sizes at 10%, 50% and 90% of the cumulative volume % distribution, respectively, when measured by a laser scattering method. 2 . The lithium hydroxide-based powder according to claim 1 , wherein the lithium hydroxide-based powder comprises lithium carbonate in an amount of at most 2 wt % relative to the weight of the lithium hydroxide-based powder. 3 . The lithium hydroxide-based powder according to claim 2 , wherein the content of the lithium carbonate relative to the weight of the lithium hydroxide-based powder is at most 1.5 wt %. 4 . The lithium hydroxide-based powder according to claim 2 , wherein the content of the lithium carbonate relative to the weight of the lithium hydroxide-based powder is at most 0.8 wt %.

5. The lithium hydroxide-based powder according to any one of the preceding claims, wherein the span is at most 4.

0.

6. The lithium hydroxide-based powder according to any one of the preceding claims, wherein the span is at most 3.

5.

7. The lithium hydroxide-based powder according to any one of the preceding claims, wherein the lithium hydroxide-based powder contains lithium hydroxide in an amount of at least 98% by weight relative to the weight of the lithium hydroxide-based powder.

8. The lithium hydroxide-based powder according to any one of the preceding claims, wherein D50 is at least 1 μm and at most 30 μm.

9. The lithium hydroxide-based powder according to any one of the preceding claims, wherein D50 is at least 5 μm and at most 20 μm.

10. A composition comprising a lithium hydroxide-based powder according to any one of the preceding claims and a transition metal hydroxide or oxyhydroxide comprising M', wherein M' comprises: -Ni with content x, where x ≥ 30.0 at% relative to M'; - Co content y, where 0.0 ≤ y ≤ 60.0 at% relative to M'; - Mn in an amount z, where 0.0 ≤ z ≤ 80.0 at% relative to M'; and - a content a of D, wherein 0.0 ≤ a ≤ 5.0 at % relative to M', wherein D is at least one element selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, where x+y+z+a is 100.0 at%.

11. A method of manufacturing a lithium hydroxide-based powder according to any one of the preceding claims, the method comprising: - drying the lithium-containing compound in a vacuum oven or in an oven under an atmosphere free of carbon dioxide to form a dried lithium-containing compound; as well as - pulverizing the dried lithium-containing compound in a pulverizer, wherein the pulverizer is under a carbon dioxide-free atmosphere and a dry air atmosphere.

12. The method of claim 11, wherein drying is performed at a temperature of at least 70°C for a period of at least 30 minutes.

13. The method according to claim 11 or 12, wherein the pulverizer is a jet mill and a gas containing no carbon dioxide is sprayed into the jet mill, and wherein the volume flow rate of the gas containing no carbon dioxide is in the range of 0.1 to 20.0 m / s. 3 / min, the grinding pressure is in the range of 1 to 10 bar, and the feed rate of the dried lithium-containing compound is in the range of 20 to 60 kg / hr. The method according to claim 13 , wherein the carbon dioxide-free gas is nitrogen.

15. The method according to any one of claims 11 to 14, wherein the drying air has a relative humidity of at most 1%.

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