Positive electrode active material for lithium-ion batteries, batteries containing the same, and uses thereof

Abstract

The present invention relates to a cathode active material for a lithium-ion battery, the cathode active material comprising secondary particles including primary particles, the primary particles having an average primary particle size (S1) determined by SEM image analysis, the cathode active material having an average crystallite size (S2) determined by X-ray diffraction measurement, wherein S1 / S2 is at least 13, and the cathode active material has been processed with an aqueous solution.

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for a lithium-ion battery. More specifically, the present invention relates to a positive electrode active material for a lithium-ion battery, the positive electrode active material comprising secondary particles including primary particles, and reducing several factors that degrade battery performance, such as a large amount of lithium impurities, a high water content, and a high specific surface area of ​​the positive electrode active material. The present invention also relates to a battery including the positive electrode active material and the use of the battery including the positive electrode active material. [Background technology]

[0002] It is well known that lithium impurities, such as LiOH and / or Li2CO3, are generated during the preparation process of cathode active materials for lithium-ion batteries, especially when the cathode active material has a Ni content of at least 60 atomic percent (at%). To reduce the lithium impurities on the surface of the cathode active material, the cathode active material is treated with an aqueous solution. The aqueous treatment results in an increased specific surface area of ​​the cathode material. However, the increase in specific surface area can lead to undesirable side reactions between the cathode active material and the electrolyte, resulting in poor battery cycle life. Furthermore, the increase in specific surface area of ​​the cathode active material can also lead to an increase in the water content on the surface of the cathode active material. Therefore, a cathode active material with a low amount of lithium impurities, a low water content, and a low specific surface area is needed. Summary of the Invention [Problem to be solved by the invention]

[0003] A first object of the present invention is to provide a positive electrode active material having a small amount of lithium impurities, a low water content, and a low specific surface area.

[0004] A second object of the present invention is to provide a battery containing the above-mentioned positive electrode active material.

[0005] A third object of the present invention is to provide for the use of the above-described battery in an electric or hybrid electric vehicle.

[0006] Acknowledgments This invention was supported by the Materials / Components Technology Development Program through the Korea Institute for Industrial Technology Evaluation, funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea). [Project Name: Development of high power (high discharge rate) lithium-ion secondary batteries with 8C-rate class / Project Number: 20011287 / Contribution Rate: 100%] [Means for solving the problem]

[0007] The first object of the present invention is achieved by providing a positive electrode active material for a lithium-ion battery, the positive electrode active material comprising secondary particles including primary particles, the primary particles having an average primary particle size (S1) determined by SEM image analysis, the positive electrode active material having an average crystallite size (S2) determined by X-ray diffraction measurement, S1 / S2 being at least 13, and the positive electrode active material being treated with an aqueous solution.

[0008] The second object of the present invention is achieved by providing a battery containing the above-mentioned positive electrode active material.

[0009] A third object of the present invention is achieved by providing the use of the above-described battery in an electric or hybrid electric vehicle. [Brief explanation of the drawings]

[0010] [Figure 1a] Figure 1a is an SEM image of EX2.1 showing a secondary particle containing multiple primary particles. The dotted line indicates the area that is captured to obtain the average primary particle size of the secondary particles. [Figure 1b] Figure 1b is an SEM image of EX2.1 to obtain the average primary particle size of the secondary particles of EX2.1. [Figure 2] FIG. 2 is an SEM image of precursor B to obtain the average primary particle size of precursor B. [Figure 3]FIG. 3 is an SEM image of precursor A to obtain the average primary particle size of precursor A. [Figure 4] FIG. 4 is an SEM image of precursor C to obtain the average primary particle size of precursor C. [Figure 5] FIG. 5 is an SEM image of precursor D to obtain the average primary particle size of precursor D. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following detailed description, preferred embodiments are described in detail to enable the practice of the invention. Although the invention has been 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 in light of the following detailed description.

[0012] positive electrode active material In a first aspect, the present invention relates to an active cathode material for a lithium-ion battery, the active cathode material comprising secondary particles comprising primary particles, the primary particles having an average primary particle size (S1) determined by SEM image analysis, and the active cathode material having an average crystallite size (S2) determined by X-ray diffraction measurement, wherein S1 / S2 is at least 13.

[0013] The present inventors have discovered that adjusting the S1 / S2 ratio of a positive electrode active material can reduce the amount of lithium impurities, water content, and specific surface area of ​​the positive electrode active material. S1 / S2 can be adjusted to be at least 13. That is, the amount of lithium impurities, water content, and specific surface area of ​​a positive electrode active material having an S1 / S2 ratio of at least 13 ("CAM1") are less than the amount of lithium impurities, water content, and specific surface area of ​​a positive electrode active material having an S1 / S2 ratio of less than 13 ("CAM2"), and CAM1 and CAM2 have the same metal composition. The lithium impurities in the positive electrode active material can be LiOH and / or Li2CO3.

[0014] The primary particle size, the average of which is S1, is calculated using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA). The specific method for calculating the primary particle size is described in the following section, "Experimental Methods Used in the Examples, E) Particle Size, E2) Primary Particle Size Analysis of Positive Electrode Active Material."

[0015] The average crystallite size, S2, is determined by XRD measurement of secondary particles of the positive electrode active material. A specific method for determining S2 is described in the following section, "Experimental Methods Used in the Examples, F) X-ray Powder Diffraction, F2) Calculation of Crystallite Size."

[0016] The amount of lithium impurities in the positive electrode active material is determined by measuring the soluble base content by pH titration. The soluble base content refers to the content of base in an aqueous solution formed by dissolving the positive electrode active material, which has not been treated with a base-containing aqueous solution, in deionized water. The soluble base content increases as the Ni content of the positive electrode active material increases. The specific method for measuring the soluble base content is described in the following section, "Experimental Methods Used in the Examples, B) Surface Base Analysis."

[0017] The water content of the positive electrode active material is measured using a Karl Metrohm Fischer Coulometer. The water content increases as the Ni content of the positive electrode active material increases. The specific method for measuring the water content is described in the following section, "Experimental Methods Used in the Examples, C) Moisture Analysis."

[0018] In a preferred embodiment, S1 / S2 may be 15-40, preferably 17-30.

[0019] In a preferred embodiment, S1 may be in the range of 100 nm to 1000 nm, preferably 200 nm to 800 nm, more preferably 300 nm to 600 nm.

[0020] In a preferred embodiment, S2 may be in the range of 5 nm to 50 nm, preferably 10 nm to 40 nm, and more preferably 15 nm to 35 nm.

[0021] In a preferred embodiment, the positive electrode active material may be treated with an aqueous solution and then dried. The treatment of the positive electrode active material with an aqueous solution can be performed by immersing the positive electrode active material in the aqueous solution. The specific surface area of ​​the positive electrode active material is increased by the treatment.

[0022] In a preferred embodiment, the aqueous solution-treated cathode active material has a maximum of 3.5 m as measured by the BET method. 2 / g, preferably up to 3.3 m 2 / g, and at least 2.0 m 2 / g, preferably at least 2.5 m 2 The BET method is specifically described in the following section, "Experimental Methods Used in the Examples, D) Specific Surface Area Analysis."

[0023] In a preferred embodiment, the positive electrode active material comprises Li, M′, and oxygen, where M′ comprises: Ni with a content x, where x ≥ 60.0 at% relative to M', Co with a content y, where 0.0≦y≦30.0 at% relative to M′, Mn with a content z, where 0.0≦z≦30.0 at.% relative to M′, D with a content a (wherein 0.0≦a≦5.0 at% with respect to M′, and 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), x+y+z+a is 100.0 at%.

[0024] In certain preferred embodiments, D is at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr.

[0025] In the foregoing embodiments, x may preferably be at least 70.0 at% relative to M', more preferably at least 80.0 at% and most preferably at least 85.0 at%; y may preferably be greater than 0.0 at% to less than or equal to 10.0 at%, more preferably greater than 2.0 at% to less than or equal to 8.0 at%, and most preferably greater than 3.0 at% to less than or equal to 6.0 at% relative to M'; and / or z may preferably be greater than 0.0 at% to less than or equal to 15 at%, more preferably greater than 2.0 at% to less than or equal to 13.0 at%, and most preferably greater than 5.0 at% to less than or equal to 11.0 at% relative to M'.

[0026] Within the framework of the present invention, at% means atomic percentage. At% or "atomic percentage" of a given element means the percentage of atoms of said 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 wt% (E wt1 ) can be converted from

[0027]

number

[0028] In a preferred embodiment, the median diameter D50 of the secondary particles of the positive electrode active material is at least 2.0 μm and at most 15.0 μm, as determined by laser diffraction particle size analysis.

[0029] In a preferred embodiment, the positive electrode active material may be represented by general formula (I):

[0030] Li b Ni x1 Co y1 Mn z1 D a1 O2(I) (Wherein, x1+y1+z1+a1 is 1.00, x1≧0.6, preferably x1≧0.7, more preferably x1≧0.8, and most preferably x1≧0.85, 0.0≦y1≦0.3, preferably 0.0≦y1≦0.1, more preferably 0.02≦y1≦0.08, and most preferably 0.03≦y1≦0.06, 0.0≦z1≦0.3, preferably 0.0≦z1≦0.15, more preferably 0.02≦z1≦0.13, and most preferably 0.05≦z1≦0.11, 0.00≦a1≦0.05, preferably 0.00≦a1≦0.04, more preferably 0.00≦a1≦0.03, and most preferably 0.00≦a1≦0.02; 0.90≦b≦1.20, preferably 0.93≦b≦1.15, more preferably 0.95≦b≦1.10, and most preferably 0.97≦b≦1.05; and D is an element selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr.

[0031] The positive electrode active material according to the present invention is feeding a stream of metal salt solution containing one or more metal elements into a reactor for a period of time (T1-T2); mixing the metal salt solution with an aqueous solution containing one or more alkali hydroxides and an aqueous ammonia solution (NH(aq)) during a period (T1-T2) to form an aqueous slurry containing hydroxide or oxyhydroxide particles of one or more metal elements; Here, during the period (T1 to T2), in the reactor, a range of pH values ​​of the aqueous slurry of 11.5 or more and 12.0 or less, preferably 11.6 or more and 11.9 or less, wherein the pH value of the aqueous slurry is the pH value measured on a sample of the aqueous slurry after cooling to 20°C; a concentration of NH3(aq) equal to or greater than 5.0 g / l, preferably equal to or less than 15.0 g / l, and maintaining the temperature of the aqueous slurry at least 70°C and at most 99°C; After a period (T1-T2), the aqueous slurry in the reactor is further processed by separating the solid fraction from the liquid fraction and drying the solid fraction to obtain a secondary particle-based powder material compound; mixing a powder material comprising a secondary particle-based powder material compound, a lithium source, and an optional dopant source to obtain a mixture; heating the mixture in an oxidizing atmosphere at a temperature of 650°C to 1000°C to obtain a raw cathode active material; and optionally further comprising a step of heat treatment before the mixing step, wherein the powder material is heated at a temperature of 105°C to 750°C.

[0032] In a preferred embodiment, the process further comprises treating the raw cathode active material with an aqueous solution.

[0033] The pH value can be measured using a pH meter, for example a 780 Metrohm meter. The NH3(aq) concentration can be measured using a commercially available titrator, for example a Metrohm 848 Titrino Plus.

[0034] The powder material containing the secondary particle-based powder material compound in the process of preparing the positive electrode active material according to the present invention is called a precursor.

[0035] In the process for preparing the cathode active material according to the present invention, the hydroxide may be partially oxidized depending on the atmosphere of the manufacturing process. Therefore, the aqueous slurry may contain oxyhydroxide. Also, during drying of the solid fraction, the hydroxide or oxyhydroxide particles from the aqueous slurry may be further partially oxidized. It should be noted that atmospheric conditions are not required to obtain the precursor.

[0036] The secondary particle-based powder compound may be an M-hydroxide or an M-oxyhydroxide, wherein M comprises one or more metal elements including at least one of Ni, Co, and Mn; the secondary particles include a plurality of primary particles, the compound has a median particle size D50 of 3.0 μm to 20.0 μm as determined by laser diffraction; the primary particles have a particle-based thickness distribution determined by measuring the thickness of the primary particles in images taken by SEM, the thickness distribution having a median particle thickness of 180 nm to 600 nm; The compound has a span value (D90-D10) / D50 of at most 0.6, preferably at most 0.4, more preferably at most 0.2, where D10, D50, and D90 are the particle size values ​​at 10%, 50%, and 90%, respectively, of the cumulative distribution.

[0037] The thickness of the primary particles was calculated using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA). The specific method for calculating the thickness of the primary particles is described in the following section, "Experimental Methods Used in the Examples, E) Particle Size, E3) Primary Particle Size Analysis of Precursors, Steps 1) to 4)."

[0038] The thickness corresponding to the cumulative percentage of the thickness distribution when it reaches 50% is designated as p50. Similarly, the thickness corresponding to the cumulative percentage of the thickness distribution when it reaches 75% is designated as p75. The thickness distribution may have a p50 in the range of 200 nm to 580 nm, preferably 220 nm to 570 nm. The thickness distribution may have a p75 in the range of 225 nm to 800 nm, preferably 250 nm to 750 nm. The disclosed ranges of p50 and / or p75 may indicate a dense structure of primary particles. The cumulative percentage of the thickness distribution is calculated based on primary particle thickness data obtained using ImageJ software (ImageJ 1.52a, National Institutes of Health, USA). Specific methods for calculating the cumulative percentage of the thickness distribution are described in the following sections, "Experimental Methods Used in the Examples, E) Particle Size, E3) Primary Particle Size Analysis of Precursors, Steps 5) and 6)."

[0039] battery In a second aspect, the present invention relates to a battery comprising an active cathode material according to the first aspect.

[0040] Battery use In a third aspect, the invention relates to the use of a battery according to the second aspect in an electric or hybrid electric vehicle.

[0041] As will be appreciated by those skilled in the art, all embodiments directed to cathode active materials according to the first aspect apply mutatis mutandis to the second and third aspects.

[0042] Experimental methods used in the examples The following analytical methods are used in the examples.

[0043] A) Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) As described below in this specification, the content of metal elements in the precursor and the positive electrode active material is 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 for 380 minutes until the sample is completely dissolved.° The solution is heated on a hot plate at 37°C. After cooling to room temperature, the solution and rinse water in the Erlenmeyer flask are transferred to a 250 mL volumetric flask. The volumetric flask is then filled with DI water up to the 250 mL mark, followed by thorough homogenization. An appropriate amount of the solution is pipetted and transferred to a 250 mL volumetric flask for the second dilution, and the volumetric flask is filled with the internal standard solution and 10% hydrochloric acid up to the 250 mL mark, followed by homogenization. Finally, this solution is used for ICP-OES measurement. The content of each metal element is expressed as wt% of the total content of the metal elements.

[0044] B) 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 untreated positive electrode active material powder is 4 grams. After stirring, the suspension of the powder in water is filtered to dissolve the base and obtain a clear solution. Step (b): pH titration: 90 mL of the clear solution prepared in step (a) is used for pH titration 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 base dissolved in the deionized water is assumed to be either LiOH (amount 2*EP1-EP2) or Li2CO3 (amount 2*(EP2-EP1)). The values ​​obtained for LiOH and Li2CO3 are the result of the reaction of the surface with deionized water.

[0045] C) Moisture analysis The moisture content of the positive electrode active material powder is measured using a Karl Metrohm Fischer Coulometer. One gram of the positive electrode active material powder is placed in a KF furnace at 300°C. The evaporated moisture is introduced into the KF reactor and analyzed by KF coulometry.

[0046] D) Specific surface area analysis D1) Measurement of specific surface area before treatment with aqueous solution The specific surface area of ​​the positive electrode active material is measured by the Braunaer-Emmet-Teller (BET) method using a Micromeritics Tristar II 3020. Before the measurement, the powder sample is heated at 300°C for 1 hour under nitrogen (N2) gas to remove adsorbed species. The dried powder is placed in a sample tube. The sample is then degassed at 30°C for 10 minutes. The instrument performs a nitrogen adsorption test at 77K. The nitrogen adsorption / desorption isotherm is obtained, and the specific surface area is measured in units of m 2 The total specific surface area of ​​the sample in g is derived.

[0047] D2) Measurement of specific surface area after treatment with aqueous solution The specific surface area of ​​the aqueous solution-treated cathode active material is obtained by mixing 7 grams of the cathode active material with 70 grams of water for 10 minutes, followed by drying in a vacuum oven at 120°C for 3 hours.

[0048] The specific surface area of ​​the dry powder is measured by the Braunaer-Emmet-Teller (BET) method using a Micromeritics Tristar II 3020. Before the measurement, the powder sample is heated at 300°C for 1 hour under nitrogen (N2) gas to remove adsorbed species. The dry powder is placed in a sample tube. The sample is then degassed at 30°C for 10 minutes. The instrument performs a nitrogen adsorption test at 77K. The nitrogen adsorption / desorption isotherm is obtained, and the specific surface area is measured in units of m 2 The total specific surface area of ​​the sample in g is derived.

[0049] E) Particle size E1) Secondary particle size analysis The secondary particle size distribution of both the precursor and the cathode active material is measured using a Malvern Mastersizer 3000 equipped with a Hydro MV wet dispersion accessory after dispersing the precursor or cathode active material powders of the examples described herein below in an aqueous medium. Sufficient sonication and agitation are applied, and a suitable surfactant is incorporated, to improve powder dispersion. D50 is defined as the particle size at 50% of the cumulative volume percent distribution.

[0050] E2) Primary particle size analysis of positive electrode active material The diameter of the primary particles of the positive electrode active material is calculated using ImageJ software (ImageJ 1.52a, US National Institutes of Health) according to the following steps: Step 1) Open a file containing a 10,000x SEM image of the cathode active material (the image was taken at the center of a secondary particle). An example of such an image is shown in Figure 1a, where the dotted line indicates the capture area corresponding to Figure 1b. Step 2) Set the scale according to the SEM magnification. Step 3) Use the polygon selection tool to draw lines that follow the edges of the primary particles for at least 50 particles. When truncating, particles at the edges of the image will be excluded. Step 4) Measure the area of ​​the drawn primary particle, which is selected from the Measurement Settings and Area boxes. Step 5) Particles

number

[0051] E3) Primary particle size analysis of precursors The thickness of the precursor primary particles is calculated using ImageJ software (ImageJ 1.52a, US National Institutes of Health) according to the following steps: Step 1) Open the file containing the SEM image of the precursor material at 20,000x magnification. Step 2) Set the scale according to the SEM magnification. Step 3) Select the line tool and place a line on the primary particle perpendicular to the orientation of the primary particle. Step 4) Measure the thickness of the primary particle selected from the Measurement Settings and Area boxes. The thickness is shown in the Length column. Step 5) Repeat processes 3 and 4 for 90 randomly selected particles in one image. If the number of particles in one image is less than 90, additional SEM images can be used. Figure 2 shows an example of the measurement of precursor B. Step 6) Process the data in Microsoft Excel or any numerical processing software as shown in Table 1 according to the following steps: a. In the "Thickness" column, sort the primary particle thickness from smallest to largest. b. In the "Total Fraction" column, calculate the fraction of each thickness that contributes to the total thickness c. In the "Cumulative" column, calculate the cumulative fraction. d. Calculate p50 and p75 from the two closest cumulative numbers, respectively, by the linear equation y=mx+c.

[0052] [Table 1]

[0053] F) X-ray powder diffraction (XRD) F1) XRD measurement X-ray diffraction patterns for the example positive electrode active material powders described herein below were collected on a Rigaku Ultima 4 X-ray diffractometer using a Cu Kα radiation source (40 kV, 40 mA) emitting at a wavelength of 1.5418 Å. The instrument configuration was set to a 1° Soller slit (SS), a 10 mm divergence height limiting slit (DHLS), a 1° divergence slit (DS), and a 0.3 mm receiving slit (RS). The goniometer diameter was 185 mm. For XRD, diffraction patterns were acquired in the range of 40 to 80° (2θ), with a scan rate of 1° per minute and a step size of 0.02° per scan.

[0054] F2) Calculation of crystallite size The average crystallite size is determined by XRD measurement of the secondary particles of the positive electrode active material. This correlates well with the average size of the primary particles contained in the secondary particles of the positive electrode active material. Therefore, the average crystallite size obtained by XRD is often used as a relevant parameter to estimate the primary particle size of the secondary particles.

[0055] The average crystallite size of the secondary particles of the example positive electrode active materials described herein below is determined according to the following steps: Step 1) Collect the diffractogram of standard LaB6 material (99.5%, Alfa Aesar from Fisher Scientific) according to the XRD measurement described in F1. Step 2) Collect the diffractogram of the positive electrode active material according to the XRD measurement described in F1. Step 3) Peak integration is performed for the LaB6 peaks at 2θ between 47° and 51° and the positive electrode active material peaks at 2θ between 42° and 47°. Peak integration is performed in Origin 2018b version b9.5.5.409, and the baseline is set to a line and area between 42.7° and 45.7°. From this step, the integrated peak areas of LaB6 and the positive electrode active material are obtained.

number

number

[0056]

number

[0057]

number

[0058] [Table 2]

[0059] In the calculations, the y0 offset is always zero because the input data is linearly baselined to 0. The peak positions are organized to place Kα1 at a lower 2θ than Kα2. m u and w are set as 0.5 and 0.2, respectively. The XRD peak area in the range of 42° to 47° is assumed to be a triangle with a base of 1.5° and the maximum intensity of the baselined peak as the height of the triangle. The Kα1 area is 2 / 3 of the calculated total XRD peak area, and the Kα2 area is 1 / 3 of the calculated total XRD peak area. the purpose The minimum value of SUMXMY2 is set as the objective in the Solver calculation. This function returns the sum of the squares of the differences between two array values. In this case, the difference is between the real and calculated values. Goodness of Fit R 2 If reaches 99.5% or more, the calculation is terminated. Otherwise, the iteration continues to reach the desired minimum value.

[0060] The diffractogram of LaB6 is shown in Figure 1. An example of the XRD peaks of EX1.1 after the fitting process is shown in Figure 2 (x-axis: 2θ, y-axis: intensity). The calculated parameters are shown in Table 2.2.

[0061] [Table 3]

[0062] From this step, the maximum intensities of the Kα1 peaks of LaB6 and the positive electrode active material were obtained, and the I LaB6 and I 活物質 is labeled as Step 5) Calculate the integral width according to the following formula:

[0063]

number

[0064]

number

number

[0065] The present invention is further illustrated in the following examples:

[0066] [Comparative Example 1] The positive electrode active material CEX1.1 was prepared through a solid-state reaction between a lithium source and a precursor according to the following steps: 1. Preparation of Precursor A: A starting solution was prepared by adding 2.0 L of DI water and 15 mL of 220 g / L NH3(aq) to a 3.65 L reactor and adjusting the temperature in the reactor to 65°C and maintaining this temperature throughout the process. The pH of the starting solution was adjusted by adding 230 g / L NaOH. (aq) The value was adjusted to 12.9 by adding solution. Next, a 220 g / L NH3(aq) and 230 g / L NaOH(aq) solution was injected at approximately 30 kW / m for the first 20 hours. 3 power density of about 10 kW / m for the rest of the process. 3The precipitation reaction was carried out by adding metal sulfate solutions of 129 g / L NiSO4(aq), 80 g / L MnSO4(aq), and 80 g / L CoSO4(aq) while mixing at a power density of 1000 kJ / min. The metal sulfate solutions were each added using separate pumps through a static mixer. The Ni:Mn:Co ratio was 98:2:0 at the beginning of the process and gradually changed to 74.1:20.3:5.6 toward the end of the precipitation process. During the reaction, the feed rate of the NaOH solution was adjusted to maintain the pH value of the reaction mixture in the reactor at a constant value of 11.6-11.8, and the feed rate of NH3(aq) was adjusted to maintain the NH3 concentration in the reaction mixture at a constant value of 8.0 ± 1 g / L. 100 minutes after the start of the reaction, it was stopped, and the reaction mixture, i.e., the aqueous slurry, was removed from the reactor. Then, 183 mL of the slurry and 1640 mL of mother liquor were returned to the reactor, and the precipitation continued. Reactor samples of the reaction mixture were taken every two hours and the D50 was measured therefrom. The reaction was stopped when the D50 of the reactor sample reached a target value of approximately 10 μm, and the duration of the process was 56 hours. During the process, a portion of the liquid fraction of the reaction mixture was pumped out of the reactor using a concentrator to obtain a slurry with a solids content of 1100 g / L. The resulting aqueous slurry of metal hydroxides was filtered and washed with 220 g / L NaOH(aq) solution and DI water at 60° C. The filter cake was dried in an oven at 120° C. for 12 hours to obtain Ni 0.85 Mn 0.10 Co 0.05 A precursor A having a total metal composition of FIG. 3 is an SEM image of precursor A to obtain the average primary particle size of precursor A. 2. Mixing: Precursor A prepared from step 1) was mixed with LiOH and Nb2O5 in an industrial blender to obtain a first mixture with 1 mol% Nb and a lithium-to-metal ratio of 1.01. 3. Heating: The mixture from step 2) was heated at 705°C under oxygen atmosphere for 12 hours, followed by grinding and sieving to obtain CEX1.1.

[0067] Positive electrode active material CEX1.2 was prepared according to the same method as CEX1.1, except that the heating temperature in step 3) was 755°C.

[0068] [Example 1] The positive electrode active material EX1.1 was prepared through a solid-state reaction between a lithium source and a precursor according to the following steps:

[0069] 1. Preparation of precursor B: Precursor B was prepared according to the same method as precursor A prepared in CEX1, except that the temperature in the reactor was maintained at 85°C. 2. Mixing: Precursor B prepared from step 1) was mixed with LiOH and Nb2O5 in an industrial blender to obtain a first mixture with 1 mol% Nb and a lithium-to-metal ratio of 1.01. 3. Heating: The mixture from step 2) was heated at 705°C under oxygen atmosphere for 12 hours, followed by grinding and sieving to obtain EX1.1.

[0070] Positive electrode active material EX1.2 was prepared according to the same method as EX1.1, except that the heating temperature in step 3) was 755°C.

[0071] Comparative Example 2 The positive electrode active material CEX2.1 was prepared through a solid-state reaction between a lithium source and a precursor according to the following steps: 1. Preparation of Precursor C: 6 L of DI water, 160 mL of 220 g / L NH3(aq), and Ni with a D50 of 5.0 μm 0.94 Mn 0.03 Co 0.03 The starting solution was prepared by adding 100 mL of a 440 g / L aqueous slurry containing (OH)2 seed particles to a 10 L reactor and adjusting the temperature in the reactor to 75 °C, which was maintained throughout the process. Next, a 220 g / L NH3(aq) and 230 g / L NaOH(aq) solution was injected at approximately 30 kW / m for the first 6 hours. 3 power density of approximately 20 kW / m for the remaining process steps. 3The precipitation reaction was carried out by adding 120 g / L of a metal sulfate solution containing Ni, Mn, and Co (in a stoichiometric molar ratio of Ni:Mn:Co 94:3:3) while mixing at a power density of 1000 rpm. The feed rate of the metal sulfate solution was 135 mL / h at the start and continuously increased to maintain a constant particle growth rate of 0.4 μm / h. During the reaction, the feed rate of the NaOH(aq) solution was adjusted to maintain a constant pH value of 11.2 ± 0.1 in the reaction mixture, and the feed rate of the NH(aq) solution was adjusted to maintain a constant NH(aq) concentration in the reaction mixture at 5.0 ± 1 g / L. Reactor samples of the reaction mixture were taken every 2 hours, and the D50 values ​​were measured from them. The reaction was stopped when the D50 value of the reactor sample reached the target value of approximately 10.0 μm. The process duration was 12 hours. During the process, an external concentrator was used to pump part of the liquid fraction of the reaction mixture out of the reactor, and the solids content of the reaction mixture in the reactor was about 390 g / L at the end of the process. The resulting aqueous slurry of metal hydroxide was filtered and washed with 220 g / L NaOH solution and DI water at 60° C. The filter cake was dried in an oven at 120° C. for 12 hours to obtain Precursor C. FIG. 4 is an SEM image of precursor C to obtain the average primary particle size of precursor C. 2. Mixing: Precursor C prepared from step 1) was mixed with LiOH, Nb2O5, and Al2O3 in an industrial blender to obtain a first mixture with 0.52 mol% Nb, 0.5 mol% Al, and a lithium-to-metal ratio of 1.03. 3. Heating: The mixture from step 2) was heated at 700°C for 12 hours under oxygen atmosphere, followed by crushing and sieving to obtain the raw cathode active material. 4. Water treatment: The raw cathode material from step 3) was immersed in water and dried to obtain CEX2.1.

[0072] Positive electrode active material CEX2.2 was prepared according to the same method as CEX2.1, except that the heating temperature in step 3) was 720°C.

[0073] Positive electrode active material CEX2.3 was prepared according to the same method as CEX2.1, except that the heating temperature in step 3) was 740°C.

[0074] [Example 2] The positive electrode active material EX2.1 was prepared through a solid-state reaction between a lithium source and a precursor according to the following steps: 1. Preparation of Precursor D: 6 L of DI water, 350 mL of 220 g / L NH3(aq), and Ni with 5.0 μm D50 0.94 Mn 0.03 Co 0.03 The starting solution was prepared by adding 400 mL of a 440 g / L aqueous slurry containing (OH)2 seed particles to a 10 L reactor and adjusting the temperature in the reactor to 85 °C, which was maintained throughout the process. The precipitation reaction was then carried out by adding a 120 g / L metal sulfate solution containing Ni, Mn, and Co (in a stoichiometric molar ratio of Ni:Mn:Co 94:03:03) while mixing 220 g / L NH3(aq) and 230 g / L NaOH(aq) solutions at a power density of approximately 30 kW / m3 for the first 6 hours and approximately 20 kW / m3 for the remaining process steps. The feed rate of the metal sulfate solution was 540 mL / h at the start and continuously increased to maintain a constant particle growth rate of 0.5 μm / h. During the reaction, the feed rate of the NaOH solution was adjusted to maintain a constant pH value of 11.7 ± 0.1 in the reactor, and the feed rate of NH3(aq) was adjusted to maintain a constant NH3 concentration of 12.0 ± 1 g / L in the reaction mixture. Reactor samples of the reaction mixture were taken every 2 hours, and the D50 was measured from them. The reaction was stopped when the D50 of the reactor sample reached the target value of approximately 10.0 μm, and the duration of the process was 11 hours. During the process, an external concentrator was used to pump a portion of the liquid fraction of the reaction mixture out of the reactor, and the solid content of the reaction mixture in the reactor was approximately 180 g / L at the end of the process. The resulting aqueous slurry of metal hydroxide was filtered and washed with 220 g / L NaOH(aq) solution and DI water at 60° C. The filter cake was dried in an oven at 120° C. for 12 hours to obtain Precursor D. FIG. 5 is an SEM image of precursor D to obtain the average primary particle size of precursor D. 2. Mixing: Precursor D prepared from step 1) was mixed with LiOH, Nb2O5, and Al2O3 in an industrial blender to obtain a first mixture having 0.52 mol% Nb, 0.5 mol% Al, and a lithium-to-metal ratio of 1.03. 3. Heating: The mixture from step 2) was heated at 700°C for 12 hours under oxygen atmosphere, followed by crushing and sieving to obtain the raw cathode active material. 4. Water treatment: The raw cathode material from step 3) was immersed in water and dried to obtain EX2.1.

[0075] Positive electrode active material EX2.2 was prepared according to the same method as EX2.1, except that the heating temperature in step 3) was 720°C.

[0076] Positive electrode active material EX2.3 was prepared according to the same method as EX2.1, except that the heating temperature in step 3) was 740°C.

[0077] result

[0078] [Table 4]

[0079] [Table 5]

[0080] Table 3 summarizes the precursor properties. Precursors B and D exhibit significantly thicker primary particles, as indicated by the p50 and p75 numbers, compared to precursors A and C. Each of precursors A through D is lithiated into cathode active materials whose properties are summarized in Table 4.

[0081] CEX1.1, CEX1.2, EX1.2, and EX1.2 have the same metal composition, i.e., Ni:Mn:Co = 85:10:5 (at%). The ratio of primary particle size (measured by SEM images (S1)) to crystallite size (measured by XRD (S2)) (S1 / S2) is observed to be larger for EX1.1 and EX1.2 compared to CEX1.1 and CEX1.2. In particular, the ratio (S1 / S2) for EX1.1 and EX1.2 is greater than 13, while the ratio (S1 / S2) for CEX1.1 and CEX1.2 is smaller than 13. This higher ratio (S1 / S2) is associated with lower total base and moisture absorption during exposure to air. The total base and moisture absorption indicate undesirable surface impurities that can cause problems during application of the cathode active material in electrochemical cells, such as gelation during slurry formation and gasification during cycling.

[0082] The same observations as for EX2.1 to EX2.3 apply to CEX2.1 to CEX2.3. CEX2.1 to CEX2.3 and EX2.1 to EX2.3 have the same metal composition, i.e., Ni:Mn:Co = 94:3:3 (at%). EX2.1 to EX2.3 prepared from precursor D exhibit a higher S1 / S2 ratio and therefore a lower total base and water content compared to CEX2.1 to CEX2.3. In addition to the benefits of a lower total base and water content, the specific surface area of ​​EX2.1 and EX2.3 is 4.0 m compared to CEX2.1 and CEX2.3 after contacting the positive electrode active material with water. 2 Even before contacting the cathode active material with water, the specific surface areas of EX2.1 and EX2.3 are lower than those of CEX2.1 and CEX2.3. The specific surface areas of EX2.1 and EX2.3 treated with water are approximately 3.2 m 2 A low surface area is preferred to prevent moisture and carbon uptake when the positive electrode active material is exposed to air, reducing the risk of side reactions with the electrolyte in the battery.

Claims

1. A positive electrode active material for a lithium ion battery, the positive electrode active material comprising secondary particles including primary particles, the primary particles have an average primary particle size (S1) determined by SEM image analysis; the positive electrode active material has an average crystallite size (S2) determined by X-ray diffraction measurement, S1 / S2 is at least 13; S2 is in the range of 5 nm to 50 nm, The positive electrode active material is treated with an aqueous solution.

2. 2. The positive electrode active material according to claim 1, wherein S1 / S2 is 15 to 40.

3. 3. The positive electrode active material according to claim 1, wherein S1 / S2 is 17 to 30.

4. 4. The positive electrode active material according to claim 1, wherein S1 is in the range of 100 nm to 1000 nm, preferably 200 nm to 800 nm, more preferably 300 nm to 600 nm.

5. The positive electrode active material according to any one of claims 1 to 4, wherein S2 is 10 nm to 40 nm, preferably 15 nm to 35 nm.

6. The positive electrode active material includes Li, M′, and oxygen, and M′ is: Ni with a content x, where x≧60.0 at% relative to M′; a Co content y, where 0.0≦y≦30.0 at% with respect to M′; Mn with a content z (where 0.0≦z≦30.0 at% relative to M′), D with a content a (wherein 0.0≦a≦5.0 at% relative to M′, and 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); The positive electrode active material according to any one of claims 1 to 5, wherein x + y + z + a is 100.0 at%.

7. 7. The positive electrode active material according to claim 6, wherein x is 70 at. % with respect to M'.

8. 8. The positive electrode active material according to claim 6, wherein x is 80 at. % or more relative to M'.

9. 9. The positive electrode active material according to claim 6, wherein y satisfies 0<y≦10 at. % with respect to M'.

10. 10. The positive electrode active material according to claim 6, wherein z is 0<z≦15 at. % with respect to M′.

11. 11. The cathode active material of claim 1, wherein the median diameter D50 of the secondary particles is at least 2.0 μm and at most 15.0 μm, as determined by laser diffraction particle size analysis.

12. A battery comprising the positive electrode active material according to any one of claims 1 to 11.

13. 13. Use of the battery of claim 12 in an electric or hybrid electric vehicle.

Images