Lithium hydroxide-based powder for use in preparing a lithium composite oxide, composition comprising the same and a transition-metal hydroxide or oxyhydroxide, and method of manufacturing the same

Abstract

The present invention relates to a lithium hydroxide-based powder for use in 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 particle sizes at 10%, 50%, and 90% of cumulative volume% distribution when measured by laser scattering method, respectively.

Description

[0001] Lithium hydroxide-based powder for use in preparing a lithium composite oxide, composition comprising the same and a transition-metal hydroxide or oxyhydroxide, and method of manufacturing the same

[0002] TECHNICAL FIELD AND BACKGROUND

[0003] 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, which is used to prepare a lithium composite oxide, wherein electrochemical properties such as capacity fading of a lithium-ion battery comprising 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 of manufacturing the lithium hydroxide-based powder.

[0004] The lithium composite oxide has been used as a positive electrode active material for a lithium-ion battery. 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 having enhanced electrochemical properties, the effect not only of the precursor but also of the lithium hydroxide-based powder on the electrochemical properties of the lithium-ion battery should be confirmed. That is, a lithium hydroxide-based powder which can enhance electrochemical properties of a lithium-ion battery is required.

[0005] It is a first object of the present invention to provide a lithium hydroxide-based powder for use in preparing a lithium composite oxide, which enhances the electrochemical properties of a lithium-ion battery comprising the lithium composite oxide.

[0006] It is a second object of the present invention to provide a composition comprising the above- mentioned lithium hydroxide-based powder and a transition-metal hydroxide or oxyhydroxide.

[0007] It is a third object of the present invention to provide a method of manufacturing the above- mentioned lithium hydroxide-based powder.

[0008] SUMMARY OF THE INVENTION

[0009] The first object of the present invention is achieved by providing a lithium hydroxide-based powder for use in 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 DIO, D50, and D90 being defined as particle sizes at 10%, 50%, and 90% of cumulative volume% distribution when measured by laser scattering method, respectively. 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:

[0010] Ni in a content x, wherein x > 30.0 at%, relative to M';

[0011] Co in a content y, wherein 0.0 < y < 60.0 at%, relative to M';

[0012] Mn in a content z, wherein 0.0 < z < 80.0 at%, relative to M'; and

[0013] D in a content a, 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, wherein x+y+z+a is 100.0 at%.

[0014] The third object of the present invention is achieved by providing a method of manufacturing the above-mentioned lithium hydroxide-based powder comprising: drying a lithium containing compound in a vacuum oven or in an oven under a carbon dioxide-free atmosphere to form a dried lithium containing compound; and pulverizing the dried lithium containing compound in a pulverizer, wherein the pulverizer is under a carbon-dioxide free atmosphere and a dry air atmosphere.

[0015] DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following detailed description, preferred embodiments are described in detail to enable practice of the present invention. Although the present invention is described with reference to these specific preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. In contrast, the present invention includes 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 use in preparing a lithium composite oxide, wherein the lithium source material has a span of at most 5.0, wherein the lithium source material comprises a lithium hydroxide, and wherein the span is defined as (D90-D10) / D50, and D10, D50, and D90 are defined as particle sizes at 10%, 50%, and 90% of cumulative volume% distribution when measured by laser scattering method, respectively. Since the lithium source material comprises a lithium hydroxide, the lithium source material may be referred to as a lithium hydroxide-based powder.

[0019] The inventors have found that electrochemical properties such as capacity fading of a lithium- ion battery are improved by using the lithium source material whose span is adjusted to be at most 5.0. In detail, if a lithium source material whose span exceeds 5.0 is used for preparing a lithium composite oxide, the crystals of the lithium composite oxide grow excessively, the particle size distribution of the lithium composite oxide becomes broad to cause agglomeration of fine particles of the lithium composite oxide, and thus, the capacity fading of a lithium-ion battery comprising the lithium composite oxide becomes deteriorated.

[0020] In a preferred embodiment, the lithium source material comprises a lithium carbonate in a content of at most 2 wt.% relative to a weight of the lithium source material. In detail, if the content of the lithium carbonate exceeds 2 wt.% relative to a weight of the lithium source material, the crystal growth of the lithium composite oxide comprising the lithium source material becomes excessively depressed, and thus, the capacity fading of a lithium-ion battery comprising the lithium composite oxide becomes deteriorated. However, even if the content of a lithium carbonate does not exceed 2 wt.% relative to a weight of the lithium source material, the capacity fading of a lithium-ion battery comprising the lithium composite oxide may not have a desired value if the span of the lithium source material exceeds 5.0. Accordingly, it is preferable to control the content of a lithium carbonate to be at most 2 wt.% relative to a weight of a lithium source material while also controlling the span of the lithium source material to be at most 5.0.

[0021] In a preferred embodiment, the lithium carbonate is in a content of 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 lithium hydroxide is in a content of 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 pm and at most 30 pm, preferably at least 5 pm and at most 20 pm, more preferably at least 7 pm and at most 18 pm, most preferably at least 10 pm and at most 16 pm. If D50 of the lithium source material exceeds 30 pm, the reactivity between the lithium source material and the precursor is lowered. If D50 of the lithium source material is below 1 pm, the lithium source material is not easy to be handled because its flowability is excessively reduced.

[0025] Composition In a second aspect, the present invention relates to a composition comprising the lithium source material according to the first aspect and a transition-metal hydroxide or oxyhydroxide comprising M', wherein M' comprises:

[0026] Ni in a content x, wherein x > 30.0 at%, relative to M';

[0027] Co in a content y, wherein 0.0 < y < 60.0 at%, relative to M';

[0028] Mn in a content z, wherein 0.0 < z < 80.0 at%, relative to M'; and

[0029] D in a content a, 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, wherein x+y+z+a is 100.0 at%.

[0030] In a preferred embodiment, the lithium source material is mixed with the transition-metal hydroxide or oxyhydroxide that the ratio of lithium to the transition-metal should range from 0.98 to 1.02. The composition is heated to obtain a lithium composite oxide used for a positive electrode active material.

[0031] In the framework of the present invention, at% signifies atomic percentage. The at% or "atomic percent" of a given element means a percentage of atoms of said element among all atoms in a claimed composition. ICP-OES provides weight percent (wt%) of each element included in a material whose composition is determined by this technique. Conversion from wt% to at% is as follows: at% of a first element Ei (Eati) in a material can be converted from a given wt% of said first element Ei (Ewti) in said material by applying the following formula, wherein Eawiis a standard atomic weight of the first element Ei, Ewti is wt% of an ithelement Ei, EaWiis a standard atomic weight of said ithelement Eizand n is an integer which represents the number of types of all elements included in the material.

[0032] Method of Manufacturing Lithium Hydroxide-based Powder

[0033] In a third aspect, the present invention relates to a method of manufacturing the lithium source material according to the first aspect comprising: drying a lithium containing compound in a vacuum oven or in an oven under a carbon dioxide-free atmosphere to form a dried lithium containing compound; and pulverizing the dried lithium containing compound in a pulverizer, wherein the pulverizer is under a carbon-dioxide free atmosphere and a dry air atmosphere.

[0034] The step of drying is performed to reduce a moisture content in the lithium source material because water molecule inhibits lithium in the lithium source material to react with the precursor. Also, the step of drying is performed in a vacuum oven or in an oven under a carbon dioxide-free atmosphere such that lithium in the lithium source material should not uptake carbon to generate lithium carbonate during the step of drying.

[0035] In a preferred embodiment, the step of drying is performed in 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 in a temperature of at most 300 °C, preferably at most 280 °C, more preferably of at most 240 °C, most preferably at most 210 °C. Drying is performed for at least 30 minutes, preferably at least 40 minutes, more preferably at least 50 minutes, and for at most 90 minutes, preferably at most 80 minutes, more preferably at most 70 minutes.

[0036] The step of pulverizing is a process, where mechanical energy is applied to reduce the dried lithium containing compound. Pulverizing is preferably a dry milling, wherein the dried lithium containing compound is pulverized in its dry state, i.e., in the absence of a liquid medium.

[0037] In a preferred embodiment, the pulverizer is a jet mill, which reduces particle size by using a jet of a compressed gas to impact particles into one another or the walls 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 at most 5.0 by using a jet mill. Furthermore, in a preferred embodiment, carbon dioxide-free gas is injected into the jet mill as a compressed gas such that lithium in the lithium source material should not uptake carbon to generate lithium carbonate. Also, a volume flow rate of the carbon dioxide-free gas ranges preferably from 0.1 to 20.0 m3 / min, more preferably from 1 to 15 m3 / min; a grinding pressure ranges preferably from 1 to 10 bar, more preferably from 3 to 7 bar; and a feeding rate of the dried lithium containing compound ranges preferably from 20 to 60 kg / hr, more preferably from 30 to 50 kg / hr.

[0038] In a preferred embodiment, the carbon dioxide-free gas during at least one of the steps of drying and pulverizing is nitrogen.

[0039] In a preferred embodiment, the dry air in the pulverizer has a relative humidity of at most 1%.

[0040] As appreciated by a person skilled in the art, all embodiments directed to the positive electrode active material according to the first aspect may apply mutatis mutandis to the second and third aspects.

[0041] EXPERIMENTAL TESTS USED IN THE EXAMPLES

[0042] The following analysis methods are used in the Examples: A) Inductively coupled plasma - optical emission analysis (ICP-OES)

[0043] The contents of the elements in positive electrode active material examples and comparative example as described herein below are measured by the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method using an Ag i I lent ICP 720-OES. 1 gram of a powder sample is dissolved into 50 mL high purity hydrochloric acid in an Erlenmeyer flask. The flask is covered by a watch glass and heated on a hot plate at 380°C until complete dissolution of the sample. After being cooled to room temperature, the solution and the rinsing water of Erlenmeyer flask are transferred to a 250 mL volumetric flask. Afterwards, the volumetric flask is filled with DI 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 2nddilution, where the volumetric flask is filled with internal standard and 10% hydrochloric acid up to the 250 mL mark and then homogenized. Finally, this solution is used for ICP-OES measurement. The contents of Ni, Mn, Co, and Si are expressed as wt.% of the total of these contents. Another suitable solvent can be used to fully dissolve the positive electrode active material powder samples.

[0044] B) Particle size distribution

[0045] The particle size distribution is measured using a Malvern Mastersizer 3000 with Hydro MV wet dispersion accessory after dispersing examples as described herein below of positive electrode active material powders in an aqueous medium. To improve the dispersion of the positive electrode active material powder examples, sufficient ultrasonic irradiation and stirring is applied, and an appropriate surfactant is introduced. Percentile values D10, D50, and D90 are the value of the particle diameter at 10%, 50% and 90%, respectively, in the cumulative distribution. A span value of the hydroxide is a value of (D90-D10) / D50.

[0046] C) Carbon analysis

[0047] The content of carbon of the positive electrode active material powder is measured by Horiba Emia-Expert carbon / sulfur analyzer. 1 gram of the positive electrode 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 into the crucible as accelerators. The powder is heated at a programmable temperature wherein gases produced during the combustion are then analyzed by Infrared detectors. The analysis of CO2 and CO determines the carbon concentration.

[0048] D) Surface base analysis

[0049] In the measurement of soluble base content by pH titration, two steps are performed: (a) the preparation of solution, and (b) pH titration. The detailed explanation of each step is as follows: Step (a): The preparation of solution: powder is immersed in deionized water and stirred for 10 min in a sealed glass flask containing 100 mL of deionized water. The amount of positive electrode active material powder is 4 grams. After stirring, to dissolve the base, the suspension of powder in water is filtered to get a clear solution.

[0050] Step (b): pH titration: 90 mL of the clear solution prepared in step (a) is used for pH titration by using 0.1M HCI. The flow rate is 0.5 mL / minute, and the pH value is recorded each 3 seconds. The pH titration profile (pH value as a function of added HCI) shows two clear equivalence (or inflection) points. The first equivalence point (corresponding to a HCI quantity of EPl) at around pH 7.4 results from the reaction of OH' and COs2' with H+. The second equivalence point (corresponding to a HCI quantity of EP2) at around pH 4.7 results from the reaction of HCO3' with H+. It is assumed that the dissolved base in deionized water is either LiOH (with a quantity 2*EP1-EP2) or IJ2CO3 (with a quantity 2*(EP2-EP1)). The obtained values for LiOH and U2CO3 are the result of the reaction of the surface with deionized water.

[0051] E) Coin cell testing

[0052] El) Coin cell preparation

[0053] For the preparation of a positive electrode, a slurry that contains a positive electrode active material powder, conductor (Super P, Timcal), binder (KF 9305, Kureha) - with a formulation of 96.5: 1.5:2.0 by weight - in a solvent (NMP, Mitsubishi) is prepared by a high-speed homogenizer. The homogenized slurry is spread on one side of an aluminum foil using a doctor blade coater with a 170 pm gap. The slurry coated foil is dried in an oven at 120°C and then pressed using a calendaring tool. Then it is dried again in a vacuum oven to completely remove the remaining solvent in the electrode film. A coin cell is assembled in an argon-filled glovebox. A separator (Celgard 2320) is located between a positive electrode and a piece of lithium foil used as a negative electrode. IM LiPFe in EC / DMC (1:2) is used as electrolyte and is dropped between separator and electrodes. Then, the coin cell is completely sealed to prevent leakage of the electrolyte.

[0054] E2) Testing method

[0055] The testing method is a conventional "constant cut-off voltage" test. The conventional coin cell test in the present invention follows the schedule shown in Table 1. Each cell is cycled at 25°C using a Toscat-3100 computer-controlled galvanostatic cycling station (from Toyo).

[0056] The schedule uses a 1C current definition of 220 mA / g in the 4.3 V to 3.0 V / Li metal window range. The capacity fading rate (QF) is obtained according to below equation. 100 wherein DQ1 is the discharge capacity at the first cycle, DQ7 is the discharge capacity at the 7th cycle, DQ34 is the discharge capacity at the 34th cycle.

[0057] Table 1. Cycling schedule for Coin cell testing method

[0058] EXAMPLES

[0059] The present invention is further illustrated in the following examples:

[0060] Example 1

[0061] A lithium hydroxide-based powder EXI was prepared according to below condition:

[0062] 1. Drying: the lithium raw material LiOH.HzO (LiOH = 57 wt.%, D50> 250 pm, span> 1.3 ) was dried in a paddle dryer with a flow of carbon dioxide free air with relative humidity < 1% (dry air). The drying temperature is 180-200°C and drying time is around 1 hour. The injection air flow is around 15 m3 / h.

[0063] 2. Milling: the dried material from step 1) was milled in a fluidized jet mill with a grinding pressure of 3 - 6 bar using dry air. Milling was done until D50 target is achieved. The obtained lithium hydroxide-based powder EXI having D50 around 11.3 pm and span around 2.85.

[0064] A positive electrode active material EX1-C was prepared through a solid-state reaction between a lithium source EXI and a precursor according to the following steps:

[0065] 1. Co-precipitation: a transition metal oxidized hydroxide precursor with metal composition of Nio.so no. Coo.io was prepared by a co-precipitation process in a large- scale continuous stirred tank reactor (CSTR) with mixed nickel manganese cobalt sulfates, sodium hydroxide, and ammonia.

[0066] 2. Mixing: the precursor prepared from Step 1) was mixed with EXI as the source of LiOH in an industrial blender to obtain a mixture having 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 an oxygen atmosphere followed by sieving and grinding to obtain EX1-C.

[0067] Comparative Example 1

[0068] CEX1 was prepared according to the same method as EXI, except that pristine air containing ambient moisture and carbon dioxide, was used for the milling purpose in Step 2). The obtained lithium hydroxide-based powder CEX1 having D50 around 11.4 pm and span around 2.67.

[0069] CEX1-C was prepared according to the same method as EX1-C, except that CEX1 was used as Li source in Step 2).

[0070] Comparative Example 2

[0071] CEX2 was prepared according to the same method as EXI, except that in step 2) colloid mill having grinder diameter of 150 mm is used. Milling speed was 3000 rpm at 10 pm gap and milling time was 20 minutes conducted under a dry air atmosphere. The obtained lithium hydroxide-based powder CEX1 having D50 around 29.6 pm and span around 5.09.

[0072] CEX2-C was prepared according to the same method as EX1-C, except that CEX2 was used as Li source in Step 2.

[0073] Comparative Example 3

[0074] CEX3 was prepared according to the same method as CEX2, except that air atmosphere was used for milling in Step 1) and pin mill was used in Step 2). Pin mill speed is 7000 rpm with a feed rate of 10 kg / hour and milling was conducted for around 1 hour under a pristine air atmosphere.

[0075] CEX3-C was prepared according to the same method as EX1-C, except that CEX3 was used as Li source in Step 2. Results

[0076] Table 2. Summary of the properties of EXI to CEX3.

[0077] Table 3. Summary of the properties of positive electrode active material EX1-C to CEX3-C

[0078] Table 2 summarizes the properties of the lithium hydroxide-based powder according to example and comparative examples. EXI is dried in vacuum and jet-milled using dry air. Such treatment condition enables the lithium hydroxide-based powder of EXI to have a span around 2.8 while keeping U2CO3 content under 0.6 wt.%. When a lithium hydroxide-based powder is obtained from jet-milling using pristine air as in CEX1, the U2CO3 content is higher than 2 wt.% due to the uptake of CO2 during milling. CEX2 is prepared by a low energy milling such as colloid mill and observed to have a large D50 and wider span in comparison with EXI. As for CEX3, both drying and low energy milling such as pin mill are conducted under pristine air atmosphere to produce the lithium hydroxide-based powder of CEX3 with high U2CO3 content, large D50 and wider span in comparison with EXI.

[0079] Table 3 summarizes positive electrode active material properties obtained from a lithiation process using the lithium hydroxide-based powders according to EXI to CEX3. It is observed that, in comparison with the comparative examples, EX1-C has the lowest content of carbon and lithium surface impurity indicated by U2CO3 and LiOH content. Moreover, EX1-C shows the lowest capacity fading rate QF well below the comparative examples. It can be concluded that the lithium hydroxide-based powder prepared according to the present invention is suitable to prepare a positive electrode active material with low U2CO3 content, low carbon content, and low capacity fading.

Claims

CLAIMS1. A lithium hydroxide-based powder for use in 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 DIO, D50, and D90 being defined as particle sizes at 10%, 50%, and 90% of cumulative volume% distribution when measured by laser scattering method, respectively.

2. The lithium hydroxide-based powder according to claim 1, wherein the lithium hydroxide- based powder comprises a lithium carbonate in a content of at most 2 wt.% relative to a weight of the lithium hydroxide-based powder.

3. The lithium hydroxide-based powder according to claim 2, wherein the lithium carbonate is in a content of at most 1.5 wt.% relative to the weight of the lithium hydroxide-based powder.

4. The lithium hydroxide-based powder according to claim 2 or 3, wherein the lithium carbonate is in a content of at most 0.8 wt.% relative to the weight of the lithium hydroxide-based powder.

5. The lithium hydroxide-based powder according to any one of the previous claims, wherein the span is at most 4.0.

6. The lithium hydroxide-based powder according to any one of the previous claims, wherein the span is at most 3.5.

7. The lithium hydroxide-based powder according to any one of the previous claims, wherein the lithium hydroxide-based powder contains a lithium hydroxide in a content of at least 98 wt.% relative to a weight of the lithium hydroxide-based powder.

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

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

10. A composition comprising the lithium hydroxide-based powder according to any one of the previous claims and a transition-metal hydroxide or oxyhydroxide comprising M', wherein M' comprises:Ni in a content x, wherein x > 30.0 at%, relative to M';Co in a content y, wherein 0.0 < y < 60.0 at%, relative to M';Mn in a content z, wherein 0.0 < z < 80.0 at%, relative to M'; andD in a content a, 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, wherein x+y+z+a is 100.0 at%.

11. A method of manufacturing the lithium hydroxide-based powder according to any one of the previous claims comprising: drying a lithium containing compound in a vacuum oven or in an oven under a carbon dioxide-free atmosphere to form a dried lithium containing compound; and 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 according to claim 11, wherein drying is performed in a temperature of at least 70°C and time period of at least 30 minutes.

13. The method according to claim 11 or 12, wherein the pulverizer is a jet mill and a carbon dioxide-free gas is injected into the jet mill, and wherein a volume flow rate of the carbon dioxide-free gas ranges from 0.1 to 20.0 m3 / min, a grinding pressure ranges from 1 to 10 bar, and a feeding rate of the dried lithium containing compound ranges from 20 to 60 kg / hr.

14. 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 dry air has a relative humidity of at most 1%.

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