Lithium hydroxide-based powder for use in preparing lithium composite oxide, composition containing said lithium hydroxide-based powder and transition metal hydroxide or oxyhydroxide, and method for producing same

Abstract

The present invention relates to a lithium hydroxide-based powder for use in preparing a lithium composite oxide, the lithium hydroxide-based powder having a span of at most 5.0, where 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 percent distribution, respectively, as measured by laser scattering.

Description

[Technical Field]

[0001] The present invention relates to a lithium hydroxide-based powder for use in preparing a lithium composite oxide. More specifically, the present invention relates to a lithium hydroxide-based powder used to prepare a lithium composite oxide, and the electrochemical properties, such as capacity degradation, 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. [Background technology]

[0002] Lithium composite oxides have been used as positive electrode active materials for lithium-ion batteries. Lithium composite oxides are synthesized by mixing a precursor with a lithium hydroxide-based powder to obtain a mixture and then heating the mixture to induce a reaction between the lithium hydroxide-based powder and the precursor. To design lithium-ion batteries with improved electrochemical performance, the effects of not only the precursor but also the lithium hydroxide-based powder on the electrochemical performance of lithium-ion batteries must be confirmed. That is, a lithium hydroxide-based powder that can improve the electrochemical performance of lithium-ion batteries is needed. Summary of the Invention [Problem to be solved by the invention]

[0003] A primary object of the present invention is to provide a lithium hydroxide-based powder for use in preparing lithium composite oxides that enhance the electrochemical properties of lithium ion batteries containing the lithium composite oxides.

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

[0005] A third object of the present invention is to provide a method for producing the lithium hydroxide-based powder described above. [Means for solving the problem]

[0006] The first object of the present invention is achieved by providing a lithium hydroxide-based powder for use in preparing a lithium composite oxide, the lithium hydroxide-based powder having a span of at most 5.0, where 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 percent distribution, respectively, as measured by a laser scattering method.

[0007] The second object of the present invention is achieved by providing a composition comprising the lithium hydroxide-based powder described above and a transition metal hydroxide or oxyhydroxide containing M', wherein M' is Ni with a content x, where x ≥ 30.0 at.% relative to M', and - Co with a content y, where 0.0≦y≦60.0 at% relative to M′, Mn with a content z, with 0.0≦z≦80.0 at% relative to M′, D with a content a, with 0.0≦a≦5.0 at% relative to M', D being 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, x+y+z+a is 100.0 at%.

[0008] The third object of the present invention is achieved by providing a method for producing the lithium hydroxide-based powder as described above, the method comprising: - drying the lithium-containing compound in a vacuum oven or in an oven under a carbon dioxide-free atmosphere to form a dry lithium-containing compound; - grinding the dried lithium-containing compound in a grinder, wherein the grinder is under a carbon dioxide-free atmosphere and a dry air atmosphere. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the following detailed description, preferred embodiments are described in detail to enable the practice of the invention. Although the invention will be described with reference to these particular preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. To the contrary, the invention includes numerous alternatives, modifications, and equivalents that will become apparent from consideration of the following detailed description.

[0010] Lithium hydroxide powder In a first aspect, the present invention relates to a lithium source material for use in preparing a lithium composite oxide, the lithium source material having a span of at most 5.0, the lithium source material comprising lithium hydroxide, the span being defined as (D90-D10) / D50, where D10, D50, and D90 are defined as the particle sizes at 10%, 50%, and 90% of the cumulative volume percent distribution, respectively, as measured by a laser scattering method. Because the lithium source material comprises lithium hydroxide, the lithium source material may also be referred to as a lithium hydroxide-based powder.

[0011] The inventors have found that the electrochemical properties, such as capacity degradation, of lithium-ion batteries can be improved by using a lithium source material whose span is adjusted to a maximum of 5.0. Specifically, when a lithium source material whose span exceeds 5.0 is used to prepare a lithium composite oxide, the crystals of the lithium composite oxide grow excessively, the particle size distribution of the lithium composite oxide becomes broad, and aggregation of fine particles of the lithium composite oxide occurs, thereby worsening the capacity degradation of lithium-ion batteries containing the lithium composite oxide.

[0012] In a preferred embodiment, the lithium source material contains lithium carbonate in a content of up to 2 wt % relative to the weight of the lithium source material. Specifically, if the lithium carbonate content exceeds 2 wt % relative to the weight of the lithium source material, the crystal growth of the lithium composite oxide containing the lithium source material is excessively reduced, thereby worsening the capacity degradation of the lithium ion battery containing the lithium composite oxide. However, even if the lithium carbonate content does not exceed 2 wt % relative to the weight of the lithium source material, the capacity degradation of the lithium ion battery containing the lithium composite oxide may not be desirable if the span of the lithium source material exceeds 5.0. Therefore, it is also preferable to control the lithium carbonate content to a maximum of 2 wt % relative to the weight of the lithium source material while controlling the span of the lithium source material to a maximum of 5.0.

[0013] In a preferred embodiment, lithium carbonate is present in a content of at most 1.5% by weight, preferably at most 0.8% by weight, more preferably at most 0.5% by weight, most preferably at most 0.3% by weight, relative to the weight of the lithium source material.

[0014] In preferred embodiments, the span is at most 4.0, preferably at most 3.5, more preferably at most 2.5, and most preferably at most 1.5.

[0015] In a preferred embodiment, the lithium hydroxide is present in an amount of at least 98.0% by weight, preferably at least 98.5% by weight, more preferably at least 98.2% by weight, most preferably at least 99.0% by weight, based on the weight of the lithium source material.

[0016] 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 decreases. If the D50 of the lithium source material is less than 1 μm, the fluidity of the lithium source material is excessively reduced, making it difficult to handle.

[0017] composition 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′ is Ni with a content x, where x ≥ 30.0 at.% relative to M', and - Co with a content y, where 0.0≦y≦60.0 at% relative to M′, Mn with a content z, with 0.0≦z≦80.0 at% relative to M′, D with a content a, with 0.0≦a≦5.0 at.% relative to M′, and D being 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, x+y+z+a is 100.0 at%.

[0018] In a preferred embodiment, the lithium source material is mixed with a transition metal hydroxide or oxyhydroxide in a lithium to transition metal ratio of 0.98 to 1.02. The composition is heated to obtain the lithium composite oxide used in the positive electrode active material.

[0019] Within the framework of the present invention, at% means atomic percentage. At% or "atomic percent" of a given element means the proportion of atoms of that element among 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: at% of the first element E1 in the material (E at1 ) can be calculated for a given weight percent (E wt1 ) can be converted from

number

[0020] Manufacturing method for lithium hydroxide powder In a third aspect, the present invention relates to a method for producing a lithium source material according to the first aspect, the method comprising: - drying the lithium-containing compound in a vacuum oven or in an oven under a carbon dioxide-free atmosphere to form a dry lithium-containing compound; - grinding the dried lithium-containing compound in a grinder, wherein the grinder is under a carbon dioxide-free atmosphere and a dry air atmosphere.

[0021] Since water molecules inhibit the lithium in the lithium source material from reacting with the precursor, a drying step is carried out to reduce the moisture content in the lithium source material, and the drying step is carried out in a vacuum oven or an oven under a carbon dioxide-free atmosphere, so that the lithium in the lithium source material cannot incorporate carbon to produce lithium carbonate during the drying step.

[0022] 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., and most preferably at least 170° C., and at most 300° C., preferably at most 280° C., more preferably at most 240° C., and 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, and more preferably at most 70 minutes.

[0023] The step of grinding is a process in which mechanical energy is applied to reduce the dry lithium-containing compound. The grinding is preferably dry milling, in which the dry lithium-containing compound is ground in its dry state, i.e., in the absence of a liquid medium.

[0024] In a preferred embodiment, the pulverizer is a jet mill, which reduces particle size by using a jet of compressed gas to collide particles with each other or with the wall of the jet mill, thereby pulverizing the particles. The span of the lithium source material according to the first aspect may be controlled to be up to 5.0 by using a jet mill. Furthermore, in a preferred embodiment, a carbon dioxide-free gas is injected into the jet mill as a compressed gas so that the lithium in the lithium source material cannot incorporate carbon to produce lithium carbonate. Also, the volumetric flow rate of the carbon dioxide-free gas is preferably 0.1 to 20.0 m 3 / min, preferably 1 to 15m 3 / min, the grinding pressure is preferably in the range of 1 to 10 bar, more preferably 3 to 7 bar, and the feed rate of the dry lithium-containing compound is preferably in the range of 20 to 60 kg / h, more preferably 30 to 50 kg / h.

[0025] In a preferred embodiment, the carbon dioxide-free gas during at least one of the drying and grinding steps is nitrogen.

[0026] In a preferred embodiment, the dry air in the mill has a maximum relative humidity of 1%.

[0027] As will be appreciated by those skilled in the art, all embodiments directed to cathode active materials according to the first aspect may be applied mutatis mutandis to the second and third aspects.

[0028] Experimental Tests Used in the Examples The following analytical methods are used in the examples.

[0029] A) Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) The elemental contents of the positive electrode active material examples and comparative examples described herein below are measured by inductively coupled plasma-optical emission spectroscopy (ICP-OES) using an Agilent ICP 720-OES. One gram of powder sample is dissolved in 50 mL of high-purity hydrochloric acid in an Erlenmeyer flask. The flask is covered with a watch glass and heated on a hot plate at 380 °C until the sample is completely dissolved. After cooling to room temperature, the solution in the Erlenmeyer flask and the rinse water are transferred to a 250 mL volumetric flask. The volumetric flask is then filled to the 250 mL mark with DI water, followed by thorough homogenization. An appropriate amount of the solution is pipetted and transferred to a 250 mL volumetric flask for a second dilution. The volumetric flask is then filled to the 250 mL mark with an internal standard and 10% hydrochloric acid, followed by homogenization. Finally, this solution is used for ICP-OES measurement. The contents of Ni, Mn, Co, and Si are expressed as weight percent relative to the total of these contents. Another suitable solvent can be used to completely dissolve the positive electrode active material powder sample.

[0030] B) Particle size distribution Particle size distribution is measured using a Malvern Mastersizer 3000 equipped with a Hydro MV wetting and dispersing attachment after dispersing examples of the cathode active material powder described herein below in an aqueous medium. Sufficient ultrasonic irradiation and agitation are applied and a suitable surfactant is introduced to improve the dispersibility of the cathode active material powder examples. The percentile values ​​D10, D50, and D90 are the particle diameter values ​​at 10%, 50%, and 90% of the cumulative distribution, respectively. The span value for hydroxide is the value (D90-D10) / D50.

[0031] C) Carbon analysis The carbon content of the cathode active material powder is measured using a Horiba Emia-Expert carbon / sulfur analyzer. One gram of cathode active material powder is placed in a ceramic crucible in a high-frequency induction furnace. 1.5 grams of tungsten and 0.2 grams of tin are added to the crucible as promoters. The powder is heated at a programmable temperature, and the gases produced during combustion are then analyzed by an infrared detector. Analysis of CO2 and CO determines the carbon concentration.

[0032] D) Surface base analysis The determination of soluble base content by pH titration involves two steps: (a) solution preparation, and (b) pH titration. A detailed description of each step follows. Step (a): Preparation of the solution: The powder is immersed in deionized water and stirred for 10 minutes in a sealed glass flask containing 100 mL of deionized water. The amount of the positive electrode active material powder is 4 grams. After stirring to dissolve the base, the suspension of the powder in water is filtered to obtain a clear solution. Step (b): pH titration: 90 mL of the clear solution prepared in step (a) is used for pH titration by using 0.1 M HCl. The flow rate is 0.5 mL / min and the pH value is recorded every 3 seconds. The pH titration profile (pH value as a function of added HCl) shows two clear equivalence points (or inflection points). The first equivalence point, around pH 7.4 (corresponding to the amount of HCl in EP1), is the first equivalence point at which OH - and CO3 2- and H+ The second equivalence point near pH 4.7 (corresponding to the amount of HCl in EP2) is - and H + The dissolved base in the deionized water is assumed to be either LiOH (2 x EP1 - EP2) or Li2CO3 (2 x (EP2 - EP1)). The values ​​obtained for LiOH and Li2CO3 are the result of the reaction of the surface with deionized water.

[0033] E) Coin Cell Test E1) Coin cell preparation To prepare the positive electrode, a slurry containing the positive electrode active material powder, conductor (Super P, Timcal), and binder (KF#9305, Kureha) in a 96.5:1.5:2.0 ratio in a solvent (NMP, Mitsubishi) was prepared using a high-speed homogenizer. The homogenized slurry was spread onto one side of an aluminum foil using a doctor blade coater with a 170 μm gap. The foil coated with the slurry was dried in an oven at 120 °C and then pressed using a calendar tool. It was then dried again in a vacuum oven to completely remove residual solvent in the electrode film. Coin cells were assembled in an argon-filled glove box. A separator (Celgard 2320) was placed between the positive electrode and a piece of lithium foil used as the negative electrode. 1 M LiPF6 in EC / DMC (1:2) was used as the electrolyte and dispensed dropwise between the separator and the electrode. The coin cell is then completely sealed to prevent electrolyte leakage.

[0034] E2) Test method The test method is a conventional "constant cutoff voltage" test. Conventional coin cell testing of 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 (manufactured by Toyo). The schedule uses a 1C current definition of 220 mA / g over the 4.3 V to 3.0 V / Li metal window range. The capacity fade rate (QF) is obtained according to the following equation:

number

[0035] [Table 1]

[0036] [Example] The present invention is further illustrated in the following examples:

[0037] Example 1 Lithium hydroxide-based powder EX1 was prepared according to the following conditions. 1. Drying: The lithium raw material LiOH.HO (LiOH = 57 wt%, D50 > 250 μm, span > 1.3) was dried in a paddle dryer using a flow of carbon dioxide-free air (dry air) with a relative humidity of < 1%. The drying temperature was 180-200 °C, and the drying time was approximately 1 hour. The inlet air flow was approximately 15 m 3 / hours. 2. Milling: The dried material from step 1) was milled in a fluidized jet mill using dry air at a grinding pressure of 3-6 bar. Milling was continued until the D50 target was achieved. The resulting lithium hydroxide-based powder EX1 has a D50 of approximately 11.3 μm and a span of approximately 2.85.

[0038] The positive electrode active material EX1-C was prepared through a solid-state reaction between the lithium source EX1 and a precursor according to the following steps. 1. Co-precipitation: Ni 0.80 Mn 0.10 Co 0.10 Transition metal oxide hydroxide precursors with metal compositions of were prepared by a co-precipitation process in a large-scale continuous stirred tank reactor (CSTR) with mixed nickel manganese cobalt sulfate, sodium hydroxide, and ammonia. 2. Mixing: The precursor prepared from step 1) was mixed with EX1 as a source of LiOH in an industrial blender to obtain a mixture with a lithium to metal ratio of 1.00. 3. Heat treatment: The mixture from step 2) was heated at 830°C for 8 hours under oxygen atmosphere, followed by sieving and grinding to obtain EX1-C.

[0039] Comparative Example 1 CEX1 was prepared according to the same method as EX1, except that fresh air containing ambient moisture and carbon dioxide was used for milling purposes in step 2. The resulting lithium hydroxide-based powder, CEX1, has a D50 of approximately 11.4 μm and a span of approximately 2.67.

[0040] CEX1-C was prepared according to the same method as EX1-C, except that CEX1 was used as the Li source in step 2).

[0041] Comparative Example 2 CEX2 was prepared in the same manner 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 with a 10 μm gap, and the milling time was 20 minutes, all in 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.

[0042] CEX2-C was prepared according to the same method as EX1-C, except that CEX2 was used as the Li source in step 2.

[0043] Comparative Example 3 CEX3 was prepared according to 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 / h, and milling was carried out for approximately 1 hour under a fresh air atmosphere.

[0044] CEX3-C was prepared according to the same method as EX1-C, except that CEX3 was used as the Li source in step 2.

[0045] result

[0046] [Table 2]

[0047] [Table 3]

[0048] Table 2 summarizes the properties of the lithium hydroxide-based powders from the Examples and Comparative Examples. EX1 was dried in a vacuum and jet-milled using dry air. These processing conditions allowed the lithium hydroxide-based powder of EX1 to have a span of approximately 2.8 while maintaining a Li2CO3 content of less than 0.6 wt%. When the lithium hydroxide-based powder was obtained by jet-milling using fresh air, as in CEX1, the Li2CO3 content was higher than 2 wt% due to CO2 uptake during milling. CEX2 was prepared by low-energy milling, such as colloid milling, and was observed to have a larger D50 and a wider span compared to EX1. For CEX3, both drying and low-energy milling, such as pin milling, were performed under a fresh air atmosphere to produce a lithium hydroxide-based powder of CEX3 with a higher Li2CO3 content, a larger D50, and a wider span compared to EX1.

[0049] Table 3 summarizes the positive electrode active material properties obtained from the lithiation process using lithium hydroxide-based powders EX1-CEX3. Compared to the comparative examples, EX1-C is observed to have the lowest content of carbon and lithium surface impurities, as indicated by the Li2CO3 and LiOH content. Furthermore, EX1-C exhibits the lowest capacity degradation rate QF, far below that of the comparative examples. It can be concluded that the lithium hydroxide-based powders prepared according to this invention are suitable for preparing positive electrode active materials with low Li2CO3 content, low carbon content, and low capacity degradation.

Claims

1. A lithium hydroxide-based powder for use in preparing a lithium composite oxide, comprising: the lithium hydroxide-based powder has a span of up to 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% cumulative volume percent distribution, respectively, as measured by laser scattering.

2. 2. The lithium hydroxide-based powder according to claim 1, wherein the lithium hydroxide-based powder contains lithium carbonate in an amount of up to 2% by weight relative to the weight of the lithium hydroxide-based powder.

3. 3. The lithium hydroxide-based powder according to claim 2, wherein the lithium carbonate is present in an amount of up to 1.5% by weight based on the weight of the lithium hydroxide-based powder.

4. 3. The lithium hydroxide-based powder according to claim 2, wherein the lithium carbonate is present in an amount of up to 0.8% by weight based on the weight of the lithium hydroxide-based powder.

5. 2. The lithium hydroxide-based powder of claim 1, wherein the span is at most 4.

0.

6. 2. The lithium hydroxide-based powder of claim 1, wherein the span is at most 3.

5.

7. 2. The lithium hydroxide-based powder according to claim 1, wherein the lithium hydroxide-based powder contains lithium hydroxide in an amount of at least 98% by weight based on the weight of the lithium hydroxide-based powder.

8. 2. The lithium hydroxide-based powder of claim 1, wherein the D50 is at least 1 μm and at most 30 μm.

9. 2. The lithium hydroxide-based powder of claim 1, wherein the D50 is at least 5 μm and at most 20 μm.

10. A composition comprising the lithium hydroxide-based powder according to any one of claims 1 to 9 and a transition metal hydroxide or oxyhydroxide containing M', wherein M' is Ni with a content x, where x≧30.0 at.% relative to M′, and - a Co content y, with 0.0≦y≦60.0 at.% relative to M′, Mn with a content z, with 0.0≦z≦80.0 at.% relative to M′, and D with a content a, with 0.0≦a≦5.0 at.% relative to M′, and D being 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, The composition wherein x+y+z+a is 100.0 at%.

11. A method for producing the lithium hydroxide-based powder according to any one of claims 1 to 9, comprising the steps of: - drying the lithium-containing compound in a vacuum oven or in an oven under a carbon dioxide-free atmosphere to form a dry lithium-containing compound; - grinding the dried lithium-containing compound in a grinder, wherein the grinder is under a carbon dioxide-free atmosphere and a dry air atmosphere.

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

13. The pulverizer is a jet mill, and a gas not containing carbon dioxide is injected into the jet mill, and the volume flow rate of the gas not containing carbon dioxide is 0.1 to 20.0 m ３ / min, the grinding pressure is in the range of 1 to 10 bar, and the feed rate of the dry lithium-containing compound is in the range of 20 to 60 kg / hr.

14. 14. The method of claim 13, wherein the carbon dioxide-free gas is nitrogen.

15. The method of claim 11 , wherein the dry air has a relative humidity of at most 1%.

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