Positive electrode active material, method for preparing the same, and positive electrode and lithium secondary battery comprising the same

Abstract

The present invention relates to a positive electrode active material, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the same, the positive electrode active material having a uniform particle size, thereby being capable of improving capacity, initial efficiency, lifespan, and resistance performance of a battery, wherein the positive electrode active material comprises a lithium nickel cobalt manganese-based oxide doped with Zr and Y in a single particle form, and has a polydispersity index (PDI) value of 1.0 to 2.0 according to Equation 1 described in the present invention.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0151124, filed with the Korean Intellectual Property Office on November 3, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a positive electrode active material, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the positive electrode active material. More specifically, it relates to a positive electrode active material having a uniform particle size, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the positive electrode active material. Background Technology

[0004] In recent years, with the technological development and increasing demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source has increased rapidly. Among these secondary batteries, lithium-ion batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0005] As positive electrode active materials for lithium-ion secondary batteries, lithium transition metal oxides have been developed, such as lithium cobalt oxides (e.g., LiCoO2), lithium nickel oxides (e.g., LiNiO2), lithium manganese oxides (e.g., LiMnO2 or LiMn2O4), and lithium iron phosphate (e.g., LiFePO4). Furthermore, in recent years, lithium composite transition metal oxides containing two or more types of transition metals, such as Li[Ni], have been developed and widely used. a Co b Mn c O2, Li[Ni a Co b Al c ]O2 and Li[Ni a Co b Mn c Al d O2.

[0006] To date, lithium composite transition metal oxides containing two or more transition metals are typically prepared as spherical secondary particles with tens to hundreds of primary particles aggregated within them. In recent years, to address the structural and thermal stability issues of secondary particle-form cathode active materials, the development of single-particle-form cathode active materials has accelerated. Specifically, when secondary particle-form cathode active materials are applied to lithium secondary batteries, a large amount of gas is generated, leading to battery volume expansion. Furthermore, increasing the nickel content in the cathode active material to achieve high capacity also increases the risk of fire. Therefore, the demand for developing single-particle-form cathode active materials with excellent stability is continuously growing.

[0007] Meanwhile, metal oxides are typically used in powder form (dry doping) as additives to improve the charge / discharge efficiency and lifetime of single-particle positive electrode active materials at high voltages. However, in the case of dry doping, the uniformity of particle growth may be suppressed due to the influence of non-uniform additives.

[0008] Therefore, it is necessary to develop positive electrode active materials in the form of single particles with uniform particle size. Summary of the Invention

[0009] Technical issues

[0010] To address the aforementioned problems, the present invention aims to provide a single-particle positive electrode active material having a uniform particle size, thereby improving battery performance.

[0011] Furthermore, another object of the present invention is to provide a method for preparing positive electrode active materials.

[0012] Furthermore, another object of the present invention is to provide a lithium secondary battery with improved performance by including the above-described positive electrode active material.

[0013] Technical solution

[0014] To achieve the above objectives, the present invention provides a positive electrode active material, a method for preparing the positive electrode active material, a positive electrode, and a lithium secondary battery.

[0015] (1) The present invention provides a positive electrode active material comprising a lithium nickel cobalt manganese-based oxide, wherein the nickel content in the lithium nickel cobalt manganese-based oxide is more than 60 mol% of all transition metals, and is in the form of a single particle consisting of less than 10 primary particles, wherein the lithium nickel cobalt manganese-based oxide is doped with zirconium (Zr) and yttrium (Y), and has a polydispersity index (PDI) value of 1.0 to 2.0 according to the following Equation 1.

[0016] [Equation 1]

[0017] PDI = Volume average particle size of primary particles (μm) / Number average particle size of primary particles (μm).

[0018] (2) In (1) above, the present invention provides a positive electrode active material, wherein the lithium nickel cobalt manganese-based oxide has a composition represented by the following chemical formula 1.

[0019] [Chemical Formula 1]

[0020] Li 1+x Ni a1 Cob1 Mn c1 Zr d1 Y e1 M f1 O2

[0021] In the above chemical formula (1), M is one or more selected from W, Cu, Sr, Mn, Ti, Mg, Mo, B, Sn, Fe, Zn, Si, and Al, and -0.1 ≤ x ≤ 0.1, 0.6 ≤ a1 < 1, 0 < b1 < 0.4, 0 < c1 < 0.4, 0 < d1 ≤ 0.01, 0 < e1 ≤ 0.01, 0 ≤ f1 ≤ 0.1, and a1 + b1 + c1 + d1 + e1 + f1 = 1.

[0022] (3) In the above (1) or (2), the present invention provides a positive electrode active material, wherein the lithium nickel cobalt manganese-based oxide is doped with 1,500 ppm to 4,500 ppm of Zr and 1,500 ppm to 4,500 ppm of Y.

[0023] (4) In any one of the above (1) to (3), the present invention provides a positive electrode active material, wherein the primary particles have a volume average particle diameter of 2.4 μm to 3.0 μm.

[0024] (5) In any one of the above (1) to (4), the present invention provides a positive electrode active material, wherein the primary particles have a number average particle diameter of 1.2 μm to 3.0 μm.

[0025] (6) In any one of the above (1) to (5), the present invention provides a positive electrode active material, wherein the D 50 of the positive electrode active material measured using a particle size analyzer (PSA) is 3.5 μm to 4.1 μm.

[0026] (7) In any one of the above (1) to (6), the present invention provides a positive electrode active material, wherein the primary particles have a span ((D v,90 -D v,10 ) / D v,50 ) value of 0.9 or less.

[0027] (8) In any one of the above (1) to (7), the present invention provides a positive electrode active material, wherein the primary particles have a D v,50 of 2.2 μm to 3.2 μm.

[0028] (9) In any one of the above (1) to (8), the present invention provides a positive electrode active material, wherein the positive electrode active material further includes a coating formed on the lithium nickel cobalt manganese-based oxide, and the coating contains Al, W, or a combination thereof.

[0029] (10) In the above (9), the present invention provides a positive electrode active material, wherein, based on the total weight of the positive electrode active material, the content of Al contained in the coating is 1,000 ppm to 2,000 ppm.

[0030] (11) In the above (9) or (10), the present invention provides a positive electrode active material, wherein, based on the total weight of the positive electrode active material, the content of W contained in the coating is 2,000 ppm to 4,000 ppm.

[0031] (12) The present invention provides a method for preparing a positive electrode active material, the method comprising: (A) mixing a composite transition metal hydroxide having a composition represented by the following Chemical Formula 2, a yttrium-containing raw material, and a lithium-containing raw material to prepare a mixture; and (B) sequentially subjecting the mixture to a first firing at 750 °C to 900 °C, a second firing at 920 °C to 1,000 °C, and then a third firing at 500 °C to 800 °C in an atmospheric atmosphere to prepare a fired product.

[0032] [Chemical Formula 2]

[0033] Ni a2 Co b2 Mn c2 Zr d2 M’ e2 (OH)2

[0034] In the above Chemical Formula 2, M’ is one or more selected from W, Cu, Sr, Mn, Y, Ti, Mg, Mo, B, Sn, Fe, Zn, Si, and Al, and 0.6 ≤ a2 < 1, 0 < b2 < 0.4, 0 < c2 < 0.4, 0 < d2 ≤ 0.01, 0 ≤ e2 ≤ 0.1, and a2 + b2 + c2 + d2 + e2 = 1.

[0035] (13) In the above (12), the present invention provides a method for preparing a positive electrode active material, wherein the first firing is carried out for 2 hours to 10 hours.

[0036] (14) In the above (12) or (13), the present invention provides a method for preparing a positive electrode active material, wherein the second firing is carried out for 2 hours to 10 hours.

[0037] (15) In the above (12) to (14), the present invention provides a method for preparing a positive electrode active material, wherein the third firing is carried out for 2 hours to 10 hours.

[0038] (16) In any of (12) to (15) above, the present invention provides a method for preparing a positive electrode active material, wherein the method further includes (C) finely pulverizing the calcined product.

[0039] (17) In the above (16), the present invention provides a method for preparing a positive electrode active material, wherein the fine grinding is carried out by vortex grinding.

[0040] (18) In (17) above, the present invention provides a method for preparing a positive electrode active material, wherein the vortex pulverization is carried out at a pressure of 2.5 bar to 5 bar.

[0041] (19) In any of (12) to (18) above, the present invention provides a method for preparing a positive electrode active material, wherein the method further comprises (C') mixing the calcined product with one or more selected from aluminum raw materials and tungsten raw materials, and then heat-treating the mixture to form a coating comprising one or more selected from Al and W on the calcined product.

[0042] (20) The present invention provides a positive electrode comprising any one of the positive electrode active materials described in (1) to (11) above.

[0043] (21) The present invention provides a lithium secondary battery comprising the positive electrode, the negative electrode, the separator disposed between the positive electrode and the negative electrode as described in (20) above, and an electrolyte.

[0044] Beneficial effects

[0045] The positive electrode active material of the present invention comprises a lithium nickel cobalt manganese-based oxide (lithium composite transition metal oxide) in the form of single particles doped with Zr and Y, and has a polydispersity index value within a specific range satisfying Equation 1 described in this specification, thereby reducing the breakage of positive electrode active material particles during rolling for manufacturing lithium secondary batteries, thereby improving the capacity, initial efficiency, lifetime and resistivity of lithium secondary batteries.

[0046] Furthermore, the above-mentioned positive electrode active material can be effectively prepared using the method for preparing positive electrode active material according to the present invention.

[0047] The positive electrode and lithium secondary battery of the present invention can be excellent in terms of capacity, initial efficiency, lifespan and resistance performance. Attached Figure Description

[0048] Figure 1 SEM images (5,000x magnification) of the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 are shown.

[0049] Figure 2This is a diagram showing SEM images (5,000×) of the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2, respectively. The images were processed to divide the particles and display the boundaries of the primary particles in random colors. Detailed Implementation

[0050] The invention will be described in more detail below to facilitate understanding of the invention.

[0051] It should be understood that the terms or words used in this specification and claims should not be construed as having the meanings defined in common dictionaries, but should be interpreted as having meanings and concepts consistent with the technical ideas of the invention, based on the inventor's ability to appropriately define the concepts of the terms to best explain the principles of the invention.

[0052] In this specification, it should be understood that the terms "comprising," "including," and "having" are intended to specify the presence of the stated features, numbers, steps, elements, or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, elements, or combinations thereof.

[0053] In this specification, the term "on" includes not only the case where a component is directly formed on the upper surface of another component, but also the case where a third component is inserted therebetween.

[0054] In this specification, "single-particle form" is a concept relative to the spherical secondary particle form, which is formed by the aggregation of tens to hundreds of primary particles manufactured by conventional methods, and refers to a form consisting of 10 or fewer primary particles. Specifically, in this invention, the single-particle form can be a single particle consisting of one primary particle, or it can be a secondary particle form consisting of an aggregation of 2 to 10 primary particles.

[0055] "Primary particle" refers to the smallest unit of particle identified when observing positive electrode active material using a scanning electron microscope, while "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles.

[0056] In this specification, the "volume average particle size of primary particles" is a value derived from Equation 2 below, and is obtained by calculating the area of ​​each primary particle by the number of pixels corresponding to each of the n primary particles present in the SEM image, using the radius (r) of a circle with the same area as the area of ​​each primary particle. i This allows for the calculation of the particle size (D) of each primary particle present in the SEM image. i =2r i ) and volume (V i =4 / 3×πr i 3The value (V) is obtained by multiplying the volume and particle size calculated for each primary particle. i D i The sum of the totals divided by the calculated volume (V) i The sum of ).

[0057] [Equation 2]

[0058] In Equation 2 above, n is the number of primary particles present in the SEM image, and V i V is the volume of one of the n primary particles, and V i D i It is the volume (V) of one of the n primary particles. i ) and particle size (D i The value obtained by multiplying ) by .

[0059] In this specification, the "average particle size of the number of primary particles" is a value derived from Equation 3 below, and is obtained by calculating the area of ​​each primary particle by the number of pixels corresponding to each of the n primary particles present in the SEM image, using the radius (r) of a circle with the same area as the area of ​​each primary particle. i This allows for the calculation of the particle size (D) of each primary particle present in the SEM image. i =2r i The total calculated particle size is then divided by the number of particles in a single operation.

[0060] [Equation 3]

[0061] In Equation 3 above, n is the number of primary particles present in the SEM image, and D i It is the particle size (D) of one of the n primary particles. i ).

[0062] In this manual, "D measured using a particle size analyzer (PSA)" 50 "D" refers to the particle size at the 50% point in the volumetric cumulative distribution of particle size. D can be measured in the following ways. 50 The powder to be measured is dispersed in a dispersion medium, and then the mixture is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac Co., Ltd.'s S3500) to calculate the particle size distribution by measuring the difference in the diffraction pattern based on the particle size as the particles pass through the laser beam. The particle size at the 50% point in the volume cumulative distribution is then calculated based on the particle size in the measuring device.

[0063] In this specification, the "D" of primary particlesv,10 D v,50 and D v,90 "This can be obtained as follows: The area of ​​each primary particle is calculated by the number of pixels corresponding to each of the n primary particles present in the SEM image. The particle size and volume of each primary particle present in the SEM image are then calculated using the radius of a circle with the same area as each primary particle. The particle size at the 10%, 50%, and 90% points in the cumulative volume distribution is then calculated based on the particle size. Furthermore, the span value of the primary particle is obtained by..." v,10 D v,50 and D v,90 Substitute (D) v,90 -D v,10 ) / D v,50 The value obtained.

[0064] Positive electrode active material

[0065] This invention provides a positive electrode active material comprising a lithium nickel cobalt manganese-based oxide, wherein the nickel content of the lithium nickel cobalt manganese-based oxide in all transition metals is 60 mol% or more, and it can be in the form of a single particle composed of 10 or fewer primary particles, wherein the lithium nickel cobalt manganese-based oxide is doped with zirconium (Zr) and yttrium (Y), and has a polydispersity index (PDI) value of 1.0 to 2.0 according to Equation 1 below. The lithium nickel cobalt manganese-based oxide may have a layered structure.

[0066] [Equation 1]

[0067] PDI = Volume average particle size of primary particles (μm) / Number average particle size of primary particles (μm)

[0068] The inventors have discovered that if the positive electrode active material comprises the above-mentioned lithium nickel cobalt manganese-based oxide in the form of single particles doped with Zr and Y, and has a polydispersity index (PDI) value within a specific range according to Equation 1 above, the breakage of the positive electrode active material particles can be reduced during rolling for manufacturing lithium secondary batteries, thereby improving the capacity, initial efficiency, lifetime and resistivity performance of lithium secondary batteries, and the inventors have completed the present invention.

[0069] According to the present invention, the nickel content in the lithium nickel cobalt manganese-based oxide can be 60 mol% or more of all transition metals. Specifically, relative to the total moles of metals other than lithium, the lithium nickel cobalt manganese-based oxide can contain 60 mol% or more or 61 mol% or more of nickel. In other words, the lithium nickel cobalt manganese-based oxide can be a high-nickel-based lithium composite transition metal oxide. In this case, the energy density of lithium secondary batteries can be improved.

[0070] According to the present invention, lithium nickel cobalt manganese-based oxides are doped with Zr and Y. In this case, the particle shape is improved and the structure is stabilized, enabling high capacity characteristics and high energy density per unit volume.

[0071] Meanwhile, when lithium nickel cobalt manganese-based oxides are not doped with Zr, the structural stability is relatively reduced during lithium insertion and extraction, which may cause problems with the life performance of lithium secondary batteries. When Y is not doped, the growth of particles requires sintering at higher temperatures, and therefore the following problem exists: the resistance of the positive electrode active material to be prepared increases.

[0072] According to the present invention, the polydispersity index (PDI) of the positive electrode active material is from 1.0 to 2.0 according to Equation 1. Theoretically, if all primary particles constituting the lithium nickel cobalt manganese-based oxide have the same particle size, the polydispersity index (PDI) is 1.0, and the more uniform the particle size, the closer the value is to 1.0. Specifically, the polydispersity index value can be 1.0 or higher, 1.1 or higher, 1.2 or higher, 1.3 or higher, 1.4 or higher, 1.5 or higher, 1.6 or higher, 1.7 or higher, or 1.8 or higher, and can be 1.9 or lower or 2.0 or lower. If the polydispersity index value meets the above range, it can be seen that the primary particles have grown very uniformly, and thus localized degradation of the positive electrode active material is prevented, thereby improving the battery performance (capacity, initial efficiency, lifetime, resistivity, etc.). The polydispersity index value is determined by a combination of the preparation method and composition of the positive electrode active material, the type of dopant element, the size and particle size distribution of the primary particles, etc., and is not determined by any single factor.

[0073] Meanwhile, if the polydispersity index of the positive electrode active material is greater than 2.0, the primary particle size is uneven, which leads to increased breakage of the positive electrode active material particles during rolling for manufacturing lithium secondary batteries, resulting in deterioration of the resistance and life performance of the lithium secondary battery.

[0074] According to the present invention, lithium nickel cobalt manganese-based oxides may have a composition represented by the following chemical formula 1.

[0075] [Chemical Formula 1]

[0076] Li 1+x Ni a1 Co b1 Mn c1 Zr d1 Y e1 M f1 O2

[0077] In the above Chemical Formula 1, M is one or more selected from W, Cu, Sr, Mn, Ti, Mg, Mo, B, Sn, Fe, Zn, Si, and Al, and -0.1 ≤ x ≤ 0.1, 0.6 ≤ a1 < 1, 0 < b1 < 0.4, 0 < c1 < 0.4, 0 < d1 ≤ 0.01, 0 < e1 ≤ 0.01, 0 ≤ f1 ≤ 0.1, and a1 + b1 + c1 + d1 + e1 + f1 = 1.

[0078] The above x can be above -0.1, above -0.09, above -0.08, above -0.07, above -0.06, above -0.05, above -0.04, above -0.03, above -0.02, above -0.01, above 0, above 0.01, above 0.02, above 0.03, or above 0.04, and can be below 0.05, below 0.06, below 0.07, below 0.08, below 0.09, or below 0.1. When x satisfies the above range, high-capacity characteristics and high energy density per unit volume can be achieved.

[0079] According to the present invention, in the above Chemical Formula 1, a1 represents the atomic fraction of nickel among the metal elements in the lithium nickel cobalt manganese-based oxide, and can be above 0.6 or above 0.61, and can be below 0.7, below 0.71, below 0.72, below 0.73, below 0.74, below 0.75, below 0.76, below 0.77, below 0.78, below 0.79, below 0.8, below 0.81, below 0.82, below 0.83, below 0.84, below 0.85, below 0.86, below 0.87, below 0.88, below 0.89, below 0.9, below 0.91, below 0.92, below 0.93, below 0.94, below 0.95, below 0.96, below 0.97, below 0.98, below 0.99, or less than 1. When a1 satisfies the above range, high-capacity characteristics can be achieved, and particularly, if a1 is from 0.6 to 0.75, high energy density is exhibited during high-voltage driving, enabling high-capacity characteristics to be achieved.

[0080] According to the present invention, in the above-mentioned chemical formula 1, b1 represents the atomic fraction of cobalt in the metal element of the lithium nickel cobalt manganese-based oxide, and can be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and can be less than 0.10, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, 0.17 or less, or 0.18 or less. Values ​​below 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or less than 0.4. When b1 meets the above ranges, stability during charging and discharging can be improved, and rate performance can be improved.

[0081] According to the present invention, in the above-mentioned chemical formula 1, c1 represents the atomic fraction of manganese in the metal element of the lithium nickel cobalt manganese-based oxide, and can be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.1 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, or 0. The electrolyte concentration (c1) can be 17 or higher, 0.18 or higher, 0.19 or higher, 0.2 or higher, 0.21 or higher, 0.22 or higher, 0.23 or higher, 0.24 or higher, 0.25 or higher, 0.26 or higher, 0.27 or higher, 0.28 or higher, 0.29 or higher, or 0.30 or higher, and can be below 0.32, below 0.33, below 0.34, below 0.35, below 0.36, below 0.37, below 0.38, below 0.39 or less than 0.4. When c1 meets the above ranges, high capacity characteristics can be achieved. Furthermore, high-temperature stability can be improved, and side reactions with the electrolyte solution can be relatively reduced.

[0082] According to the present invention, in the above-mentioned chemical formula 1, d1 represents the atomic fraction of zirconium in the metal element of the lithium nickel cobalt manganese-based oxide, and can be greater than 0, greater than 0.001, greater than 0.002, or greater than 0.003, and can be less than 0.004, less than 0.005, less than 0.006, less than 0.007, less than 0.008, less than 0.009, or less than 0.01. When d1 satisfies the above range, the crystal structure stability of the positive electrode active material can be improved, and due to the increase in structural stability, the resistance and lifespan of the battery can be improved.

[0083] According to the present invention, in the above-described chemical formula 1, e1 represents the atomic fraction of yttrium in the metal element of the lithium nickel cobalt manganese-based oxide, and can be greater than 0 or greater than 0.001, and can be less than 0.002, less than 0.003, less than 0.004, less than 0.005, less than 0.006, less than 0.007, less than 0.008, less than 0.009, or less than 0.01. When e1 satisfies the above range, particle growth can be improved, thereby improving capacity and lifespan.

[0084] According to the present invention, in the above-mentioned chemical formula 1, f1 represents the atomic fraction of element M in the metal element of the lithium nickel cobalt manganese-based oxide, and can be 0 or more, and 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When f1 satisfies the above range, the crystal structure stability of the positive electrode active material can be improved, and the particle shape can be improved.

[0085] According to the present invention, the lithium nickel cobalt manganese-based oxide is doped with 1,500 ppm to 4,500 ppm of Zr and 1,500 ppm to 4,500 ppm of Y.

[0086] The Zr content relative to the total weight of lithium nickel cobalt manganese-based oxides can be specifically 1,500 ppm or higher, 1,600 ppm or higher, 1,700 ppm or higher, 1,800 ppm or higher, 1,900 ppm or higher, 2,000 ppm or higher, 2,100 ppm or higher, 2,200 ppm or higher, 2,300 ppm or higher, 2,400 ppm or higher, 2,500 ppm or higher, 2,600 ppm or higher, 2,700 ppm or higher, 2,800 ppm or higher, or 2,900 ppm or higher, and can be below 3,000 ppm, below 3,100 ppm, below 3,200 ppm, below 3,300 ppm, below 3,400 ppm, below 3,500 ppm, below 3,600 ppm, below 3,700 ppm, below 3,800 ppm, or below 3,900 ppm. Below ppm, below 4,000 ppm, below 4,100 ppm, below 4,200 ppm, below 4,300 ppm, below 4,400 ppm, or below 4,500 ppm.

[0087] The content of Y relative to the total weight of lithium nickel cobalt manganese-based oxides can be specifically 1,500 ppm or more, 1,600 ppm or more, 1,700 ppm or more, 1,800 ppm or more, 1,900 ppm or more, 2,000 ppm or more, 2,100 ppm or more, 2,200 ppm or more, 2,300 ppm or more, or 2,400 ppm or more, and can be below 2,500 ppm, below 2,600 ppm, below 2,700 ppm, below 2,800 ppm, below 2,900 ppm, below 3,000 ppm, below 3,100 ppm, below 3,200 ppm, below 3,300 ppm, below 3,400 ppm, below 3,500 ppm, below 3,600 ppm, below 3,700 ppm, below 3,800 ppm, below 3,900 ppm, below 3,000 ppm, below 3,900 ppm, below 3,100 ppm, below 3,200 ppm, below 3,300 ppm, below 3,400 ppm, below 3,500 ppm, below 3,600 ppm, below 3,700 ppm, below 3,800 ppm, below 3,900 ppm, below 3,900 ppm. Below ppm, below 4,000 ppm, below 4,100 ppm, below 4,200 ppm, below 4,300 ppm, below 4,400 ppm, or below 4,500 ppm.

[0088] If the Y content is within the above range, the influence of Y promotes particle growth, thereby increasing the grain size and the size of primary particles, which can improve the capacity and life performance of the battery. If the Zr content is within the above range, Zr is stably doped on the transition metal layer, thereby improving the structural stability during lithium insertion and extraction, and thus the particle strength is excellent, which can improve the life and resistance performance of the battery.

[0089] According to the present invention, the primary particles may have a volume average particle size of 2.4 μm to 3.0 μm. Specifically, the volume average particle size of the primary particles may be 2.4 μm or more, or 2.5 μm or more, and may be 2.7 μm or less, 2.8 μm or less, 2.9 μm or less, or 3.0 μm or less. If the volume average particle size of the primary particles is within the above range, it is advantageous for mobile lithium, enabling improvements in battery charge / discharge capacity and efficiency, and also improving lifespan performance.

[0090] According to the present invention, the primary particles can have a number average particle size of 1.2 μm to 3.0 μm. Specifically, the number average particle size of the primary particles can be 1.2 μm or more, or 1.3 μm or more, and can be less than 1.5 μm, less than 1.6 μm, less than 1.7 μm, less than 1.8 μm, less than 1.9 μm, less than 2.0 μm, less than 2.1 μm, less than 2.2 μm, less than 2.3 μm, less than 2.4 μm, less than 2.5 μm, less than 2.6 μm, less than 2.7 μm, less than 2.8 μm, less than 2.9 μm, or less than 3.0 μm. When the number average particle size of the primary particles is within the above range, the proportion of small particles (primary particles with a particle size of less than 1 μm) related to lifetime performance is reduced, thereby improving lifetime performance.

[0091] According to the present invention, as measured by a particle size analyzer (PSA), the positive electrode active material can have a D of 3.5 μm to 4.1 μm. 50 The average particle size (D) of the positive electrode active material 50 Specifically, the particle size can be 3.50 μm or larger, 3.60 μm or larger, 3.70 μm or larger, or 3.80 μm or larger, and can be 3.90 μm or smaller, 4.00 μm or smaller, or 4.10 μm or smaller. If the D of the positive electrode active material is measured using a particle size analyzer (PSA)... 50 Within the aforementioned range, the lifespan and capacity characteristics of batteries, including the positive electrode active material, can be improved, thereby optimizing electrochemical performance. For reference, if D 50 If the diameter is less than 3.5 μm, the battery life can be reduced, while if D 50 If the diameter is greater than 4.1 μm, the battery capacity can be reduced.

[0092] According to the present invention, the primary particles may have a span of 0.9 or less (D v,90 -D v,10 ) / D v,50 The span value of a primary particle can specifically be 0 or higher, 0.10 or higher, 0.20 or higher, 0.30 or higher, 0.40 or higher, 0.50 or higher, 0.60 or higher, 0.70 or higher, or 0.80 or higher, and can be below 0.82, below 0.83, below 0.84, below 0.85, below 0.86, below 0.87, below 0.88, below 0.89, or below 0.90. If the span value of a primary particle is within the above range, it can be determined that the particle size distribution is uniform, and uniform particle growth can improve lifespan performance.

[0093] According to the present invention, the D of primary particles v,50The particle size can range from 2.2 μm to 3.2 μm. The D0 of primary particles... v,50 Specifically, the particle size can be 2.20 μm or larger, 2.25 μm or larger, 2.30 μm or larger, 2.35 μm or larger, 2.40 μm or larger, 2.45 μm or larger, 2.50 μm or larger, or 2.55 μm or larger, and can also be below 2.70 μm, below 2.75 μm, below 2.80 μm, below 2.85 μm, below 2.90 μm, below 2.95 μm, below 3.00 μm, below 3.05 μm, below 3.10 μm, below 3.15 μm, or below 3.20 μm. If the primary particle's D... v,50 Within the aforementioned range, lithium migration is advantageous, enabling improvements in charge / discharge capacity and efficiency, as well as enhancing lifetime performance.

[0094] According to the present invention, the positive electrode active material may further include a coating formed on a lithium nickel cobalt manganese-based oxide, wherein the coating may include Al, W, or a combination thereof. In this case, the conductivity of the positive electrode active material is improved, and side reactions with the electrolyte solution in the battery are suppressed, thereby improving the battery's capacity characteristics, resistance characteristics, lifespan characteristics, etc. Specifically, the generation of byproducts in the form of hydrogen fluoride, which can be produced through side reactions with the electrolyte solution in the battery, is suppressed, enabling high capacity characteristics at high rates.

[0095] According to the present invention, the Al content contained in the coating can be from 1,000 ppm to 2,000 ppm relative to the total weight of the positive electrode active material. Specifically, the Al content relative to the total weight of the positive electrode active material can be 1,000 ppm or more, 1,100 ppm or more, 1,200 ppm or more, or 1,300 ppm or more, and can be 1,400 ppm or less, 1,500 ppm or less, 1,600 ppm or less, 1,700 ppm or less, 1,800 ppm or less, 1,900 ppm or less, or 2,000 ppm or less. In this case, the conductivity of the positive electrode active material is improved, and the generation of byproducts due to side reactions with the electrolyte solution in the battery is suppressed, thereby improving the capacity characteristics, resistance characteristics, lifetime characteristics, etc., of the positive electrode active material.

[0096] According to the present invention, relative to the total weight of the positive electrode active material, the content of W contained in the coating may be 2,000 ppm to 4,000 ppm. Specifically, the content of W may be 2,000 ppm or more, 2,100 ppm or more, or 2,200 ppm or more relative to the total weight of the positive electrode active material, and may be 2,500 ppm or less, 2,600 ppm or less, 2,700 ppm or less, 2,800 ppm or less, 2,900 ppm or less, 3,000 ppm or less, 3,100 ppm or less, 3,200 ppm or less, 3,300 ppm or less, 3,400 ppm or less, 3,500 ppm or less, 3,600 ppm or less, 3,700 ppm or less, 3,800 ppm or less, 3,900 ppm or less, or 4,000 ppm or less. In this case, the conductivity of the positive electrode active material is improved, and the generation of by-products formed due to side reactions with the electrolyte solution in the battery is suppressed, enabling improvement of the capacity characteristics, resistance characteristics, life characteristics, etc. of the positive electrode active material.

[0097] Methods for preparing positive electrode active materials

[0098] The present invention provides a method for preparing the above positive electrode active material. In other words, the positive electrode active material according to the present invention is prepared by the following method for preparing a positive electrode active material.

[0099] The method for preparing the positive electrode active material in the form of single particles according to the present invention includes: (A) mixing a composite transition metal hydroxide having a composition represented by the following Chemical Formula 2, a yttrium-containing raw material, and a lithium-containing raw material to prepare a mixture; and (B) subjecting the mixture to a first firing at 750°C to 900°C, a second firing at 920°C to 1,000°C, and then a third firing at 500°C to 800°C in an atmospheric atmosphere to prepare a fired product.

[0100] [Chemical Formula 2]

[0101] Ni a2 Co b2 Mn c2 Zr d2 M’ e2 (OH)2

[0102] In the above Chemical Formula 2, M’ is one or more selected from W, Cu, Sr, Mn, Y, Ti, Mg, Mo, B, Sn, Fe, Zn, Si, and Al, and 0.6 ≤ a2 < 1, 0 < b2 < 0.4, 0 < c2 < 0.4, 0 < d2 ≤ 0.01, 0 ≤ e2 ≤ 0.1, and a2 + b2 + c2 + d2 + e2 = 1.

[0103] The inventors have discovered that if a mixture obtained by mixing a composite transition metal hydroxide containing Ni, Co, Mn, and Zr with yttrium-containing raw materials and lithium-containing raw materials is sequentially calcined at 750°C to 900°C once, calcined at 920°C to 1,000°C twice, and calcined at 500°C to 800°C three times, a positive electrode active material in the form of single particles with a uniform primary particle size can be prepared, thereby reducing the breakage of the positive electrode active material particles during rolling for manufacturing lithium secondary batteries. The inventors have completed this invention.

[0104] Step (A)

[0105] Step (A) above is a step of preparing a mixture by mixing a positive electrode active material precursor having the composition represented by the above chemical formula 2, a yttrium-containing raw material and a lithium-containing raw material.

[0106] According to the present invention, in the above chemical formula 2, a2 ​​represents the atomic fraction of nickel in the metal element in the composite transition metal hydroxide, and can be 0.6 or more or 0.61 or more, and can be less than 0.7, less than 0.71, less than 0.72, less than 0.73, less than 0.74, less than 0.75, less than 0.76, less than 0.77, less than 0.78, less than 0.79, less than 0.8, less than 0.81, less than 0.82, less than 0.83, less than 0.84, less than 0.85, less than 0.86, less than 0.87, less than 0.88, less than 0.89, less than 0.9, less than 0.91, less than 0.92, less than 0.93, less than 0.94, less than 0.95, less than 0.96, less than 0.97, less than 0.98, less than 0.99 or less than 1. When a2 meets the above range, high capacity characteristics of the battery including the positive electrode active material to be prepared can be achieved. In particular, if a2 is 0.6 to 0.75, the battery including the positive electrode active material to be prepared can exhibit high energy density during high voltage driving, thus enabling high capacity characteristics to be achieved.

[0107] According to the present invention, in the above-mentioned chemical formula 2, b2 represents the atomic fraction of cobalt in the metal element of the complex transition metal hydroxide, and can be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and can be less than 0.10, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, 0.17 or less, or 0.18 or less. The values ​​are below 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or less than 0.4. When b2 meets the above ranges, the stability of the battery, including the positive electrode active material to be prepared, during charging and discharging can be improved, and the rate performance can be improved.

[0108] According to the present invention, in the above-mentioned chemical formula 2, c2 represents the atomic fraction of manganese in the metal element of the complex transition metal hydroxide, and can be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.1 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0 The concentration of c2 can be 0.17 or higher, 0.18 or higher, 0.19 or higher, 0.2 or higher, 0.21 or higher, 0.22 or higher, 0.23 or higher, 0.24 or higher, 0.25 or higher, 0.26 or higher, 0.27 or higher, 0.28 or higher, 0.29 or higher, or 0.30 or higher, and can be 0.32 or lower, 0.33 or lower, 0.34 or lower, 0.35 or lower, 0.36 or lower, 0.37 or lower, 0.38 or lower, 0.39 or lower, or less than 0.4. When c2 meets the above ranges, high capacity characteristics of the battery including the positive electrode active material to be prepared can be achieved. Furthermore, the high-temperature stability of the battery can be improved, and side reactions with the electrolyte solution can be relatively reduced.

[0109] According to the present invention, in the above-mentioned chemical formula 2, d2 represents the atomic fraction of zirconium in the metal element of the composite transition metal hydroxide, and can be greater than 0, greater than 0.001, greater than 0.002, or greater than 0.003, and can be less than 0.004, less than 0.005, less than 0.006, less than 0.007, less than 0.008, less than 0.009, or less than 0.01. When d2 meets the above range, the crystal structure stability of the positive electrode active material to be prepared can be improved, and due to the improvement in structural stability, the resistance and lifespan of the battery can be improved.

[0110] According to the present invention, in the above-mentioned chemical formula 2, e2 represents the atomic fraction of element M in the metal element of the composite transition metal hydroxide, and can be 0 or more, and 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When e2 satisfies the above range, the crystal structure stability of the positive electrode active material to be prepared can be improved, and the particle shape can be improved.

[0111] Complex transition metal hydroxides can be prepared by co-precipitation reaction of a solution containing a complex transition metal (Ni, Co, Mn, and Zr), an alkaline aqueous solution, and an ammonium cation complex forming agent. Specifically, complex transition metal hydroxides, as precursors for positive electrode active materials, can be prepared by co-precipitation reaction simultaneously with the introduction of a reaction solution comprising a solution containing a complex transition metal, an alkaline aqueous solution, and an ammonium cation complex forming agent into a reactor.

[0112] Solutions containing complex transition metals include cations of Ni, Co, Mn, and Zr metals. Solutions containing complex transition metals may include acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, hydroxyoxides, etc., of the aforementioned metals, and there are no particular limitations, as long as they are soluble in water.

[0113] Alkaline aqueous solutions may include one or more selected from alkali metal hydrates, alkali metal hydroxides, alkaline earth metal hydrates, and alkaline earth metal hydroxides. For example, alkaline aqueous solutions may include NaOH, KOH, Ca(OH)2, etc., and water or a mixture of water and an organic solvent that can be homogeneously mixed with water can be used as a solvent.

[0114] The ammonium cation complex forming agent may include one or more selected from NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3. As a solvent, water or a mixture of water and an organic solvent (especially an alcohol, etc.) that is homogeneous with water can be used.

[0115] The coprecipitation reaction can be carried out for 1 hour to 50 hours. Specifically, the coprecipitation reaction can be carried out for more than 1 hour, 5 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, or 20 hours, and can be less than 30 hours, 31 hours, 32 hours, 33 hours, 34 hours, 35 hours, 36 hours, 37 hours, 38 hours, 39 hours, 40 hours, 45 hours, or 50 hours. If the coprecipitation reaction is carried out for a period of time within the above range, the crystallinity of the composite transition metal hydroxide particles can be controlled to a sufficient degree.

[0116] In this case, an alkaline aqueous solution can be introduced in an amount that brings the pH of the reaction solution within the desired range. The coprecipitation reaction can be carried out at a pH of 10 to 13. Specifically, the coprecipitation reaction can be carried out at pH values ​​above 10, 10.5, 11, or 11.5, as well as at pH values ​​below 12, 12.5, 12.7, or 13.

[0117] When complex transition metal hydroxide particles are formed using the method described above, the particles are separated from the reaction solution to obtain the complex transition metal hydroxide. Specifically, the reaction solution can be filtered to separate the particles, and the separated particles can then be washed with water and dried to obtain the complex transition metal hydroxide. In this case, processes such as pulverization and / or classification can be performed if necessary.

[0118] According to the present invention, the yttrium (Y)-containing raw material may be one or more selected from YCl3, Y2O3, Y(NO3)3, Y(OH)3, YSZ, Y2(SO4)3, and Y2S3, particularly one or more selected from Y2O3, Y(NO3)3, and Y(OH)3, and more particularly Y2O3. The yttrium-containing raw material may be added in an amount such that the weight of yttrium relative to the total weight of the complex transition metal hydroxide is from 1,500 ppm to 4,500 ppm. Specifically, the amount of yttrium-containing raw material added can be such that the yttrium relative to the total weight of the complex transition metal hydroxide is 1,500 ppm or more, 1,600 ppm or more, 1,700 ppm or more, 1,800 ppm or more, 1,900 ppm or more, 2,000 ppm or more, 2,100 ppm or more, 2,200 ppm or more, 2,300 ppm or more, 2,400 ppm or more, 2,500 ppm or more, 2,600 ppm or more, 2,700 ppm or more, 2,800 ppm or more, or 2,900 ppm or more, and can be below 3,000 ppm, below 3,100 ppm, below 3,200 ppm, below 3,300 ppm, below 3,400 ppm, below 3,500 ppm, below 3,600 ppm, below 3,700 ppm, or below 3,800 ppm. Below ppm, 3,900 ppm, 4,000 ppm, 4,100 ppm, 4,200 ppm, 4,300 ppm, 4,400 ppm, or 4,500 ppm. In these cases, the grain size contained in a single particle is larger, which can further improve the capacity and lifespan performance of the battery.

[0119] According to the present invention, the lithium-containing raw materials can be lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, hydroxides, hydroxyoxides, etc., and there are no particular limitations, as long as they can be dissolved in water. Specifically, the lithium-containing raw materials can be Li2CO3, LiNO3, LiNO2, LiOH, LiOH H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, etc., and any one or a mixture of two or more of them can be used.

[0120] According to the present invention, a composite transition metal hydroxide and a lithium-containing raw material can be mixed such that the ratio (M:Li) of the total number of moles of transition metals (M) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the lithium-containing raw material is 1:1.0-1.1, 1:1.01-1.09, 1:1.02-1.08, 1:1.03-1.07, 1:1.04-1.07 or 1:1.05-1.07.

[0121] Step (B)

[0122] Step (B) above involves firing the mixture sequentially at 750°C to 900°C once, at 920°C to 1,000°C a second time, and at 500°C to 800°C a third time in an atmospheric atmosphere to prepare the fired product.

[0123] According to the present invention, when the mixture is calcined once at 750°C to 900°C, a reaction occurs between the lithium-containing raw material and the composite transition metal hydroxide, thereby causing a change in the crystal structure and preparing polycrystalline secondary particles with a small primary particle size. The primary calcination temperature can specifically be above 750°C, above 760°C, above 770°C, above 780°C, above 790°C, above 800°C, above 810°C, above 820°C, above 830°C, above 840°C, or above 850°C, and can be below 860°C, below 870°C, below 880°C, below 890°C, or below 900°C. If the primary calcination temperature is within the above range, the reaction between the composite transition metal hydroxide and the lithium-containing raw material proceeds uniformly, resulting in a structurally stable and uniform positive electrode active material. If the temperature is below 750°C, the reaction between lithium and the composite transition metal hydroxide cannot proceed sufficiently, resulting in the formation of positive electrode active material in the form of secondary particles (where more than 10 primary particles aggregate during secondary firing), thus causing a deterioration in lifetime characteristics. If the temperature is above 900°C, the growth of primary particles proceeds rapidly, thereby inducing the growth of uneven particles during secondary firing, thus causing a reduction in capacity.

[0124] According to the present invention, in terms of ease of maintaining the heat treatment atmosphere and economy, the firing is carried out in an atmospheric atmosphere.

[0125] According to the present invention, a single firing process can be carried out for 2 to 10 hours. In this case, the reaction between the composite transition metal hydroxide and lithium ions proceeds sufficiently, so that even inside the positive electrode active material, a uniform distribution of lithium can be achieved, and overall uniform particle growth can be achieved.

[0126] Immediately after the first firing, if the temperature is continuously increased to 920°C to 1,000°C, and a second firing is performed at 920°C to 1,000°C, the size of the primary particles increases, allowing for the preparation of single-particle particles. If the second firing temperature is within this range, the primary particles grow sufficiently to produce single-particle cathode active materials, improving capacity and lifetime characteristics. Conversely, if the second firing temperature is below 920°C, the primary particle size is small, resulting in a non-uniform cathode active material in the form of secondary particles rather than single particles, leading to a shortened lifetime. If the temperature exceeds 1,000°C, the primary particle size becomes too large, degrading lithium migration and causing increased resistance and deteriorated capacity characteristics.

[0127] In terms of ease of maintaining the firing atmosphere and economy, the second firing is carried out in an atmospheric atmosphere.

[0128] According to the present invention, the secondary firing can be carried out for 2 to 10 hours. In this case, the primary particle growth is sufficient to improve capacity and lifespan characteristics.

[0129] Immediately after the second firing, if the temperature is continuously reduced to 500°C to 800°C, and a third firing is performed at 500°C to 800°C, a surface stabilization reaction occurs, resulting in a fired product with improved crystal structure stability. In this case, the fired product can be a lithium nickel cobalt manganese-based oxide with a nickel content of 60 mol% or more in all transition metals, and in the form of single particles consisting of fewer than 10 primary particles. If the third firing temperature is within the above range, structural stability is improved, thereby improving charge / discharge capacity and resistance. However, if the third firing temperature is below 500°C, the reduced structural stability of the positive electrode active material leads to increased cation mixing, resulting in reduced lifetime performance. Conversely, if the temperature is above 800°C, changes in surface structure lead to increased resistance and reduced charge capacity.

[0130] In terms of ease of maintaining the firing atmosphere and economy, the three firings are carried out in an atmospheric atmosphere.

[0131] According to the present invention, the three firing processes can be carried out for 2 to 10 hours. In this case, the structural stability of the positive electrode active material is improved, resulting in the advantage of increased charge / discharge capacity and efficiency.

[0132] The method for preparing positive electrode active material according to the present invention may further include (C) finely pulverizing the calcined product, thereby improving capacity by uniformly applying the positive electrode active material during electrode manufacturing.

[0133] According to the present invention, fine grinding can be performed by vortex grinding. In this case, grinding can be carried out according to the target particle size range, which is beneficial for setting particle sizes optimized for capacity and lifespan performance.

[0134] According to the present invention, vortex pulverization can be carried out at a pressure of 1.5 bar to 5 bar. In this case, the charge / discharge capacity and lifetime performance of the positive electrode active material can be improved by uniformly pulverizing without damaging the primary particles.

[0135] The method for preparing the positive electrode active material according to the present invention may further include (C') mixing the calcined product with one or more raw materials selected from aluminum and tungsten, and then heat-treating the mixture to form a coating comprising one or more of Al and W on the calcined product. In this case, a coating portion comprising one or more of Al and W is formed on the calcined product (lithium nickel cobalt manganese-based oxide in single-particle form).

[0136] According to the present invention, the amount of aluminum raw material added can be such that the aluminum content relative to the total weight of the calcined product is 1,000 ppm to 2,000 ppm. Specifically, the amount of aluminum raw material added can be such that the aluminum content relative to the total weight of the calcined product is 1,000 ppm or more, 1,100 ppm or more, 1,200 ppm or more, or 1,300 ppm or more, and can be 1,400 ppm or less, 1,500 ppm or less, 1,600 ppm or less, 1,700 ppm or less, 1,800 ppm or less, 1,900 ppm or less, or 2,000 ppm or less.

[0137] According to the present invention, the amount of tungsten raw material added can be such that the total weight of tungsten relative to the calcined product is 2,000 ppm to 4,000 ppm. Specifically, the amount of tungsten raw material added can be such that the total weight of tungsten relative to the calcined product is 2,000 ppm or more, 2,100 ppm or more, or 2,200 ppm or more, and can be less than 2,500 ppm, less than 2,600 ppm, less than 2,700 ppm, less than 2,800 ppm, less than 2,900 ppm, less than 3,000 ppm, less than 3,100 ppm, less than 3,200 ppm, less than 3,300 ppm, less than 3,400 ppm, less than 3,500 ppm, less than 3,600 ppm, less than 3,700 ppm, less than 3,800 ppm, less than 3,900 ppm, or less than 4,000 ppm.

[0138] According to the present invention, the mixing amount of aluminum raw material and tungsten raw material can make the total amount of coating elements Al and W relative to the total weight of combustion products 3,000 ppm to 6,000 ppm. Specifically, the mixing amount of aluminum and tungsten raw materials can ensure that the total amount of coating elements Al and W relative to the total weight of the fired product is above 3,000 ppm, 3,100 ppm, 3,200 ppm, 3,300 ppm, 3,400 ppm, 3,500 ppm, 3,600 ppm, 3,700 ppm, 3,800 ppm, 3,900 ppm, 4,000 ppm, 4,100 ppm, 4,200 ppm, 4,300 ppm, 4,400 ppm, or 4,500 ppm, and can be below 4,600 ppm, below 4,700 ppm, below 4,800 ppm, below 4,900 ppm, below 5,000 ppm, below 5,100 ppm, below 5,200 ppm, or below 5,300 ppm. The concentrations are below ppm, 5,400 ppm, 5,500 ppm, 5,600 ppm, 5,700 ppm, 5,800 ppm, 5,900 ppm, or 6,000 ppm. Under these conditions, the conductivity of the positive electrode active material to be prepared can be improved, and the byproducts formed due to side reactions with the electrolyte solution can be controlled, thereby improving the battery's capacity and lifespan characteristics.

[0139] Heat treatment can be carried out in an atmospheric atmosphere, an oxygen atmosphere, or an inert atmosphere. Specifically, heat treatment can be carried out in an atmospheric atmosphere because it is advantageous in terms of ease of maintenance and economy.

[0140] Furthermore, the heat treatment can be performed at temperatures ranging from 400°C to 600°C. Specifically, the heat treatment can be maintained at temperatures above 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, or 500°C, and can be maintained at temperatures below 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, or 600°C. If the heat treatment temperature is within the above range, sufficient thermal energy can be provided for the coating. If lithium nickel cobalt manganese-based oxide is mixed with Al and W coating raw materials, and then heat-treated within the above temperature range, a coating including the coating elements Al and W can be formed on the lithium nickel cobalt manganese-based oxide. The coating, including the coating elements Al and W, can be in the form of partially covering (discontinuously) at least a portion (i.e., a region on the lithium nickel cobalt manganese-based oxide) or covering (continuously) the entire region. The coating can be in the form of a film, an island, or a combination thereof.

[0141] The heat treatment can last from 3 to 9 hours. Specifically, the heat treatment can last more than 3 hours, more than 4 hours, or more than 5 hours, but can also last less than 6 hours, less than 7 hours, less than 8 hours, or less than 9 hours. If the heat treatment time is within the above range, sufficient thermal energy can be provided to form the coating.

[0142] positive electrode

[0143] The present invention provides a positive electrode comprising the above-mentioned positive electrode active material.

[0144] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the aforementioned positive electrode active material.

[0145] The positive electrode current collector can include highly conductive metals, and there are no particular limitations, as long as it does not react within the battery's voltage range and the positive electrode active material layer can easily adhere to the positive electrode current collector. Examples of positive electrode current collectors include stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. Furthermore, the positive electrode current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities can be formed on its surface to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0146] If desired, the positive electrode active material layer may optionally include conductive materials, binders, and the positive electrode active material. In this case, the content of the positive electrode active material relative to the total weight of the positive electrode active material layer may be from 80% to 99% by weight, more specifically from 85% to 98.5% by weight, and may exhibit excellent capacity performance within the aforementioned range.

[0147] Conductive materials are used to impart conductivity to the electrodes, and any conductive material can be used without particular limitation, as long as it has electronic conductivity without causing chemical changes to the components of the battery. Specific examples may include graphite, such as natural or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermally cracked carbon black, and carbon fibers; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive tubes, such as carbon nanotubes; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one or a mixture of two or more of these can be used. The content of the conductive material relative to the total weight of the positive electrode active material layer can be from 0.1% by weight to 15% by weight.

[0148] Adhesives are used to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples may include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, polymers whose hydrogens are substituted with Li, Na, or Ca, or various copolymers thereof, and any one or a mixture of two or more of them may be used. The content of the adhesive relative to the total weight of the positive electrode active material layer can be from 0.1% by weight to 15% by weight.

[0149] The positive electrode can be manufactured according to the general methods used for manufacturing positive electrodes, the difference being the use of the aforementioned positive electrode active material. Specifically, the positive electrode can be manufactured by applying a positive electrode active material layer forming composition (which is prepared by dispersing the aforementioned positive electrode active material and, if necessary, an optional binder, conductive material, and dispersant, in a solvent) onto a positive electrode current collector, followed by drying and rolling; or, casting the positive electrode active material layer forming composition onto a separate carrier, and then pressing the film layer obtained by peeling it off from the carrier onto the positive electrode current collector.

[0150] The solvent can be any solvent commonly used in the art, and can be dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, water, etc., and any one or a mixture of two or more of them can be used. Considering the coating thickness and manufacturing yield of the slurry, the amount of solvent to be used is sufficient if the solvent dissolves or disperses the positive electrode active material, conductive material, binder, and dispersant, and subsequently, when applied to manufacture the positive electrode, the slurry can have a viscosity that exhibits excellent thickness uniformity.

[0151] Lithium secondary batteries

[0152] The present invention provides a lithium secondary battery, which includes the above-mentioned positive electrode, negative electrode, separator disposed between the positive electrode and the negative electrode, and electrolyte.

[0153] Lithium secondary batteries may optionally also include a battery housing for housing electrode assemblies for a positive electrode, a negative electrode, and a separator, as well as a sealing member for sealing the battery housing.

[0154] The negative electrode may include a negative electrode current collector and a layer of negative electrode active material placed on the negative electrode current collector.

[0155] There are no particular limitations on the negative electrode current collector, as long as it has high conductivity without causing chemical changes in the battery. For example, it can be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or copper or stainless steel, aluminum-cadmium alloys, etc., surface-treated with one of carbon, nickel, titanium, silver, etc. Furthermore, the negative electrode current collector typically has a thickness from 3 μm to 500 μm, and as in the case of the positive electrode current collector, fine irregularities can be formed on its surface to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0156] In addition to the negative electrode active material, the negative electrode active material layer may selectively include a binder and a conductive material.

[0157] As anode active materials, compounds capable of reversibly inserting and deintercalating lithium can be used. Specific examples include carbonaceous materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metallic compounds that can form alloys with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and lithium-doped and undoped metal oxides, such as SiO2. β(0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composite materials including metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof may be used. Furthermore, lithium metal films can be used as anode active materials. In addition, low-crystallinity carbon, high-crystallinity carbon, etc., can all be used as carbon materials. Representative examples of low-crystallinity carbon may include soft carbon and hard carbon, and representative examples of high-crystallinity carbon may include irregular, planar, sheet-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon, such as coke derived from petroleum or coal tar pitch. Based on the total weight of the anode active material layer, the content of the anode active material can be from 80% to 99% by weight.

[0158] Adhesives are components used to aid in the bonding between conductive materials, active materials, and current collectors, and are typically added in an amount from 0.1% to 10% by weight relative to the total weight of the negative electrode active material layer. Examples of adhesives may include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, and various copolymers thereof.

[0159] The conductive material in the negative electrode active material layer is a component used to further improve the conductivity of the negative electrode active material, and can be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. There are no particular limitations on the conductive material, as long as it is conductive without causing chemical changes in the battery. Examples of suitable materials include graphite, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers and metal fibers; fluorinated carbon; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives, etc.

[0160] The negative electrode can be manufactured by applying a negative electrode active material layer forming composition (which is prepared by dissolving or dispersing the negative electrode active material and optional binder and conductive material in a solvent) onto a negative electrode current collector and then drying it; or by casting the negative electrode active material layer forming composition onto a separate carrier and then pressing the film layer obtained by peeling it off from the carrier onto the negative electrode current collector.

[0161] The separator is used to separate the negative and positive electrodes and provide a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is a separator commonly used in lithium secondary batteries. In particular, separators with excellent electrolyte moisture retention and low resistance to ion movement in the electrolyte are preferred. Specifically, porous polymer membranes can be used, for example, porous polymer membranes made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures with two or more layers. Furthermore, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. In addition, coated separators including ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0162] Electrolytes can be organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., and can be used to manufacture lithium secondary batteries, but are not limited to these. As a specific example, electrolytes may include organic solvents and lithium salts.

[0163] As organic solvents, any organic solvent can be used without particular limitation, as long as it can serve as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as organic solvents, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic C2 to C20 hydrocarbon group, and may include double-bonded aromatic rings or ether bonds); amides such as dimethylformamide; dioxolane solvents such as 1,3-dioxolane; or sulfolane. Carbonate solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant and low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) are even more preferred, which can improve the charging / discharging performance of the battery.

[0164] As a lithium salt, any compound can be used without particular limitation, as long as it can provide lithium ions for lithium secondary batteries. Specifically, the anion of the lithium salt can be selected from F... - Cl - ,Br - I- NO3 - N(CN)2 - BF4 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - At least one of the components in the group consisting of lithium salts, such as LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, and LiB(C2O4)2, can be used. The lithium salt can be used in concentrations ranging from 0.1 M to 2.0 M. If the concentration of the lithium salt is within the above range, the electrolyte exhibits suitable conductivity and viscosity, thus demonstrating excellent electrolyte performance, and lithium ions can move efficiently.

[0165] To improve battery life, suppress capacity reduction, and increase discharge capacity, the electrolyte may also include one or more additives, such as alkylene carbonate halogenates (e.g., ethylene difluorocarbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol ethers, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidinanes, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In this case, the additive content relative to the total weight of the electrolyte can be from 0.1% by weight to 5% by weight.

[0166] The lithium secondary battery of the present invention, comprising the above-mentioned positive electrode active material, has excellent performance and can therefore be used in portable devices such as mobile phones, laptops and digital cameras, as well as in electric vehicles such as hybrid electric vehicles (HEVs).

[0167] The external shape of the lithium secondary battery of the present invention is not particularly limited, but it can be cylindrical, square, bag-shaped, coin-shaped, etc.

[0168] The lithium secondary battery of the present invention can be used as a battery cell for power supply of small devices, and is also preferably used as a unit battery of large and medium-sized battery modules including multiple battery cells.

[0169] Therefore, a battery module including a lithium secondary battery as a unit cell and a battery pack including the battery module are provided.

[0170] The battery module or battery pack can be used as a power source for one or more large or medium-sized devices in power tools, electric vehicles (including electric vehicles (EVs), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEVs)) or power storage systems.

[0171] In the following, embodiments of the invention will be described in detail in a manner readily apparent to those skilled in the art. However, the invention can be embodied in many different forms and is not limited to the embodiments set forth herein.

[0172] Examples and Comparative Examples

[0173] Example 1

[0174] A composite transition metal hydroxide in the form of secondary particles formed by the aggregation of dozens to hundreds of primary particles (composition: Ni). 0.617 Co 0.06 Mn 0.32 Zr 0.003 (OH)2, average particle size (D) 50 Yttrium (Ni+Co+Mn+Zr) and Y2O3 (introduced in an amount such that yttrium is 0.3 mol% relative to the composite transition metal hydroxide) were introduced into an acoustic mixer and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes. Subsequently, Li2CO3 was introduced into the acoustic mixer such that the ratio of the total moles of transition metals (Ni+Co+Mn+Zr) in the composite transition metal hydroxide to the moles of lithium (Li) in the Li2CO3 ((Ni+Co+Mn+Zr):Li) was 1:1.06, and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes to prepare a mixture.

[0175] The mixture was introduced into a square alumina crucible (150mm×150mm) and fired once at 850℃ for 6 hours under atmospheric conditions. After the temperature was continuously increased to 955℃ (heating rate: 1.25℃ / min), it was fired a second time at 955℃ for 3 hours. Then, after the temperature was continuously decreased to 600℃ (cooling rate: 3℃ / min), it was fired a third time at 600℃ for 2 hours to prepare the fired product.

[0176] The calcined product was finely pulverized at a rate of 5 g / min using a jet mill (Isaac ENC Co., Ltd., 2-inch Jet Mill) at a sample injection pressure of 6 bar and a pulverizing pressure of 4 bar.

[0177] The finely pulverized calcined product was mixed with Al2O3 (introduced in an amount of 1,500 ppm of Al relative to the total weight of the calcined product) and WO3 (introduced in an amount of 3,000 ppm of W relative to the total weight of the calcined product), and then heat-treated at 500°C for 6 hours under atmospheric atmosphere to prepare a positive electrode active material including a coating containing Al and W.

[0178] Example 2

[0179] A composite transition metal hydroxide in the form of secondary particles formed by the aggregation of dozens to hundreds of primary particles (composition: Ni). 0.617 Co 0.06 Mn 0.32 Zr 0.003 (OH)2, average particle size (D) 50 Yttrium (Ni+Co+Mn+Zr) and Y2O3 (introduced in an amount such that yttrium is 0.3 mol% relative to the composite transition metal hydroxide) were introduced into an acoustic mixer and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes. Subsequently, Li2CO3 was introduced into the acoustic mixer such that the ratio of the total moles of transition metals (Ni+Co+Mn+Zr) in the composite transition metal hydroxide to the moles of lithium (Li) in the Li2CO3 ((Ni+Co+Mn+Zr):Li) was 1:1.06, and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes to prepare a mixture.

[0180] The mixture was introduced into a square alumina crucible (150mm×150mm) and fired once at 850℃ for 4 hours under atmospheric conditions. After the temperature was continuously increased to 945℃ (heating rate: 1.25℃ / min), it was fired a second time at 945℃ for 5 hours. Then, after the temperature was continuously decreased to 600℃ (cooling rate: 3℃ / min), it was fired a third time at 600℃ for 6 hours and 30 minutes to prepare the fired product.

[0181] The calcined product was finely pulverized at a rate of 5 g / min using a jet mill (Isaac ENC Co., Ltd., 2-inch Jet Mill) at a sample injection pressure of 6 bar and a pulverizing pressure of 4 bar.

[0182] The finely pulverized calcined product was mixed with Al2O3 (introduced in an amount of 1,500 ppm of Al relative to the total weight of the calcined product) and WO3 (introduced in an amount of 3,000 ppm of W relative to the total weight of the calcined product), and then heat-treated at 500°C for 6 hours under atmospheric atmosphere to prepare a positive electrode active material including a coating containing Al and W.

[0183] Comparative Example 1

[0184] A composite transition metal hydroxide in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles (composition: Ni) 0.62 Co 0.06 Mn 0.32 (OH)2, average particle size (D) 50 ZrO2 (introduced in an amount such that zirconium is 0.3 mol% relative to the composite transition metal hydroxide) and Y2O3 (introduced in an amount such that yttrium is 0.3 mol% relative to the composite transition metal hydroxide) were introduced into an acoustic mixer and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes. Subsequently, Li2CO3 was introduced into the acoustic mixer such that the ratio of the total moles of transition metals (Ni+Co+Mn+Zr) in the composite transition metal hydroxide to the moles of lithium (Li) in Li2CO3 ((Ni+Co+Mn+Zr):Li) was 1:1.06, and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes to prepare a mixture.

[0185] The mixture was introduced into a square alumina crucible (150mm×150mm) and fired once at 850℃ for 6 hours under atmospheric conditions. After the temperature was continuously increased to 955℃ (heating rate: 1.25℃ / min), it was fired a second time at 955℃ for 3 hours. Then, after the temperature was continuously decreased to 600℃ (cooling rate: 3℃ / min), it was fired a third time at 600℃ for 2 hours to prepare the fired product.

[0186] The calcined product was finely pulverized at a rate of 5 g / min using a jet mill (Isaac ENC Co., Ltd., 2-inch Jet Mill) at a sample injection pressure of 6 bar and a pulverizing pressure of 4 bar.

[0187] The finely pulverized calcined product was mixed with Al2O3 (Evonik Co., Ltd.) (introduced in an amount such that Al is 1,500 ppm relative to the total weight of the calcined product) and WO3 (Zenichem Co., Ltd.) (introduced in an amount such that W is 3,000 ppm relative to the total weight of the calcined product), and then heat-treated at 500°C for 6 hours under atmospheric atmosphere to prepare a positive electrode active material including a coating containing Al and W.

[0188] Comparative Example 2

[0189] A composite transition metal hydroxide in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles (composition: Ni) 0.62 Co 0.06 Mn 0.32 (OH)2, average particle size (D) 50 ZrO2 (introduced in an amount such that zirconium is 0.3 mol% relative to the composite transition metal hydroxide) and Y2O3 (introduced in an amount such that yttrium is 0.3 mol% relative to the composite transition metal hydroxide) were introduced into an acoustic mixer and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes. Subsequently, Li2CO3 was introduced into the acoustic mixer such that the ratio of the total moles of transition metals (Ni+Co+Mn+Zr) in the composite transition metal hydroxide to the moles of lithium (Li) in Li2CO3 ((Ni+Co+Mn+Zr):Li) was 1:1.06, and mixed sequentially at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes to prepare a mixture.

[0190] The mixture was introduced into a square alumina crucible (150mm×150mm) and fired once at 850℃ for 4 hours under atmospheric conditions. After the temperature was continuously increased to 945℃ (heating rate: 1.25℃ / min), it was fired a second time at 945℃ for 5 hours. Then, after the temperature was continuously decreased to 600℃ (cooling rate: 3℃ / min), it was fired a third time at 600℃ for 6 hours and 30 minutes to prepare the fired product.

[0191] The calcined product was finely pulverized at a rate of 5 g / min using a jet mill (Isaac ENC Co., Ltd., 2-inch Jet Mill) at a sample injection pressure of 6 bar and a pulverizing pressure of 4 bar.

[0192] The finely pulverized calcined product was mixed with Al2O3 (introduced in an amount of 1,500 ppm of Al relative to the total weight of the calcined product) and WO3 (introduced in an amount of 3,000 ppm of W relative to the total weight of the calcined product), and then heat-treated at 500°C for 6 hours under atmospheric atmosphere to prepare a positive electrode active material including a coating containing Al and W.

[0193] Experimental Example

[0194] Experimental Example 1: (1) Particle size analysis of positive electrode active material

[0195] SEM images (5,000x magnification) of each positive electrode active material prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were obtained using SEM (FEI Co., Ltd., Inspect F) and are shown below. Figure 1 middle.

[0196] Furthermore, the boundaries of the primary particles presented in five SEM images (5,000x magnification) of each positive electrode active material prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were separated using an image processing program (LG Chem Co., Ltd., DX program) and shown in random colors. Figure 2 The image shows SEM images (5,000x magnification) of the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2, respectively. The images were processed to divide the material and display the boundaries of the primary particles in random colors.

[0197] The area of ​​each primary particle is calculated by dividing the boundaries of the primary particles into a graph shown in random colors. The area of ​​each primary particle is calculated by the number of pixels corresponding to each of the n primary particles, and the radius (r) of a circle with the same area as each primary particle is used. i This is used to calculate the particle size (D) of each primary particle present in the SEM image. i =2ri ) and volume (V i =4 / 3×πr i 3 The value (V) is obtained by multiplying the volume and particle size calculated for each primary particle. i D i The sum of the totals divided by the calculated volume (V) i The sum of the calculated particle sizes is used to derive the volume average particle size of the primary particles. The sum of the calculated particle sizes is divided by the number of primary particles to derive the number average particle size. Then, the PDI value is obtained according to Equation 1 described in this invention. All of these are shown in Table 1 below.

[0198] Furthermore, a graph obtained by separating the boundaries of primary particles and displaying it in random colors was used to calculate the particle size at 10%, 50%, and 90% points in the cumulative volume distribution of particle size based on the calculated particle size and volume of all primary particles, thereby confirming D. v,10 D v,50 and D v,90 And D v,50 and span ((D) v,90 -D v,10 ) / D v,50 The values ​​are shown in Table 1 below.

[0199] Experimental Example 2: (2) Particle size analysis of positive electrode active material

[0200] Take 0.01 g of each positive electrode active material (powder) prepared in the examples and comparative examples, place it in a vial containing 30 ml of ultrapure water and 500 μl of dispersant, and disperse the positive electrode active material using an ultrasonic instrument for 1 minute. Then, analyze it in a PSA (Microtrac Co., Ltd., S3500) to confirm D. 50 As shown in Table 1 below.

[0201] At this time, D 50 This indicates the particle size at the 50th percentile of the volumetric cumulative distribution based on particle size.

[0202] [Table 1]

[0203] Referring to Table 1 above, compared with the positive electrode active materials of Comparative Examples 1 and 2, the positive electrode active materials of Examples 1 and 2 have a PDI value closer to 1 and a low span value, thus confirming that they have uniform particle size.

[0204] refer to Figure 1It can be confirmed that the positive electrode active materials of Examples 1 and 2 exist only in the form of single particles composed of 10 or fewer primary particles, while the positive electrode active materials of Comparative Examples 1 and 2 exist in the form of secondary particles in which primary particles smaller than the primary particles of Examples 1 and 2 aggregate, and in the form of single particles composed of primary particles that have grown to be very large.

[0205] refer to Figure 2 It can be confirmed that in the cases of Examples 1 and 2, the portion of primary particles clustered together in different colors is not large and the primary particles with uniform size are evenly distributed. However, in the cases of Comparative Examples 1 and 2, there are portions of primary particles clustered together in different colors and the individual primary particles do not have uniform size.

[0206] Experiment Example 3: ICP Analysis

[0207] Take 0.1 g of each calcined product prepared in the Examples and Comparative Examples (hereinafter referred to as lithium nickel cobalt manganese-based oxides), add 1 ml of hydrochloric acid, and then heat to dissolve the lithium nickel cobalt manganese-based oxides. Subsequently, to accelerate the reaction, a small amount of hydrogen peroxide water is added to completely dissolve the lithium nickel cobalt manganese-based oxides, thereby preparing a solution. The solution is then diluted with deionized water to a total volume of 10 mL, thereby preparing the analytical sample. The weight ratio of the constituent elements present in the analytical sample was measured using an ICP apparatus (ICP-OES; Agilent 5110, Agilent Technologies Co., Ltd.), and the composition of the lithium nickel cobalt manganese-based oxides and the contents of Zr (ppm) and Y (ppm) present in the lithium nickel cobalt manganese-based oxides are shown in Table 2 below.

[0208] In addition, 0.1 g of each positive electrode active material prepared in the examples and comparative examples was taken, 1 ml of hydrochloric acid was added, and then heated to dissolve the positive electrode active material. Subsequently, to accelerate the reaction, a small amount of hydrogen peroxide water was added to completely dissolve the positive electrode active material, thereby preparing a solution. The solution was then diluted with deionized water to a total volume of 10 mL, thereby preparing the analytical sample. The weight ratio of the constituent elements present in the analytical sample was measured using an ICP apparatus (ICP-OES; Agilent 5110, Agilent Technologies Co., Ltd.), and the content of Al (ppm) and W (ppm) present in the positive electrode active material are shown in Table 2 below.

[0209] [Table 2]

[0210] Table 2 above confirms that the lithium nickel cobalt manganese-based oxides prepared in Examples 1 and 2, and Comparative Examples 1 and 2, have a composition represented by the above-described chemical formula 1, and include doping elements Zr and Y. Furthermore, it is confirmed that the positive electrode active materials prepared in Examples 1 and 2, and Comparative Examples 1 and 2, include coatings containing Al and W.

[0211] Experiment Example 4: Evaluation of Battery Performance

[0212] Each positive electrode active material, Super P conductive material, and polyvinylidene fluoride (PVDF) binder prepared in the Examples and Comparative Examples were mixed in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 95:2:3 to prepare a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to manufacture the positive electrode.

[0213] A lithium metal electrode is used as the negative electrode, and a porous polyethylene separator is inserted between the positive and negative electrodes to prepare an electrode assembly. The electrode assembly is then placed inside a battery casing, and an electrolyte solution is injected into the battery casing to create a half-cell. The electrolyte solution is prepared by dissolving 1.0 M LiPF6 in an organic solvent (in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 3:4:3).

[0214] Each half-cell manufactured as described above was charged to 4.45 V at 25°C in CC (0.1 C)-CV mode and discharged to 2.5 V in CC (0.1 C) mode. The initial charge capacity and initial discharge capacity were measured during this period, and the initial charge / discharge capacity, initial efficiency, and DC internal resistance (DCIR) were calculated and are shown in Table 3 below. For reference, the initial efficiency value is a percentage of the initial discharge capacity relative to the initial charge capacity, and the DCIR value is calculated by dividing the difference between the voltage at 60 seconds and the initial voltage when the battery is discharged at a constant current of 0.1 C by the current.

[0215] Furthermore, the capacity of the lithium secondary battery was measured by repeatedly performing 50 charge / discharge cycles at a constant current of 0.33 C within the range of 2.5 V to 4.45 V at 45°C. The percentage of the discharge capacity of the 50th cycle relative to the discharge capacity of the first cycle was set as the capacity retention rate, as shown in Table 3 below. Additionally, the percentage of the DCIR obtained by dividing the voltage drop (ΔV) over 60 seconds in the 50th discharge cycle by the current, relative to the DCIR obtained by dividing the voltage drop (ΔV) over 60 seconds in the first discharge cycle by the current, was set as the resistance increase rate, as shown in Table 3 below.

[0216] [Table 3]

[0217] Referring to Tables 1 and 3 above, the positive electrode active materials of Examples 1 and 2 not only have a single particle form, but also have a PDI index close to 1 and a low span value. Therefore, when included in a battery, they are superior in terms of battery capacity, initial efficiency, lifespan and resistivity performance compared to batteries containing the positive electrode active materials of Comparative Examples 1 and 2.

Claims

1. A positive electrode active material comprising a lithium nickel cobalt manganese-based oxide, wherein the nickel content in all transition metals in the lithium nickel cobalt manganese-based oxide is 60 mol% or more, and it is in the form of a single particle composed of 10 or fewer primary particles, wherein the lithium nickel cobalt manganese-based oxide is doped with zirconium (Zr) and yttrium (Y), and has a polydispersity index (PDI) value of 1.0 to 2.0 according to the following Equation 1: [Equation 1] PDI = volume average particle size (μm) of primary particles / number average particle size (μm) of primary particles.

2. The positive electrode active material as described in claim 1, wherein, The lithium nickel cobalt manganese-based oxide has a composition represented by the following Chemical Formula 1: [Chemical Formula 1] Li 1+x Ni a1 Co b1 Mr c1 Zr d1 Y e1 M f1 O2 wherein in the above Chemical Formula 1, M is one or more selected from W, Cu, Sr, Mn, Ti, Mg, Mo, B, Sn, Fe, Zn, Si, and Al, and -0.1 ≤ x ≤ 0.1, 0.6 ≤ a1 < 1, 0 < b1 < 0.4, 0 < c1 < 0.4, 0 < d1 ≤ 0.01, 0 < e1 ≤ 0.01, 0 ≤ f1 ≤ 0.1, and a1 + b1 + c1 + d1 + e1 + f1 = 1.

3. The positive electrode active material as described in claim 1, wherein, The lithium nickel cobalt manganese-based oxide is doped with 1,500 ppm to 4,500 ppm of Zr and 1,500 ppm to 4,500 ppm of Y.

4. The positive electrode active material as described in claim 1, wherein, The primary particles have a volume average particle size of 2.4 μm to 3.0 μm.

5. The positive electrode active material as described in claim 1, wherein, The primary particles have a number average particle size of 1.2 μm to 3.0 μm.

6. The positive electrode active material as described in claim 1, wherein, The D of the positive electrode active material was measured using a particle size analyzer (PSA). 50 The thickness ranges from 3.5 μm to 4.1 μm.

7. The positive electrode active material as described in claim 1, wherein, The primary particles have a span value of less than 0.9, and the span value is used as (D v,90 -D v,10 ) / D v,50 get.

8. The positive electrode active material as described in claim 1, wherein, The primary particles have a D-size of 2.2 μm to 3.2 μm. v,50 .

9. The positive electrode active material as described in claim 1, wherein, The positive electrode active material further includes a coating formed on the lithium nickel cobalt manganese-based oxide, wherein the coating contains Al, W, or a combination thereof.

10. The positive electrode active material as described in claim 9, wherein, The content of Al contained in the coating is 1,000 ppm to 2,000 ppm relative to the total weight of the positive electrode active material.

11. The positive electrode active material as described in claim 9, wherein, The content of W contained in the coating is 2,000 ppm to 4,000 ppm relative to the total weight of the positive electrode active material.

12. A method for preparing a positive electrode active material, the method comprising: (A) Mixing a composite transition metal hydroxide having a composition represented by the following Chemical Formula 2, a yttrium-containing raw material, and a lithium-containing raw material to prepare a mixture; and (B) Sequentially subjecting the mixture to a first firing at 750°C to 900°C, a second firing at 920°C to 1,000°C, and then a third firing at 500°C to 800°C in an atmospheric atmosphere to prepare a fired product: [Chemical Formula 2] Ni a2 What b2 Mn c2 Zr d2 M' e2 (OH)2 wherein in the above Chemical Formula 2, M' is one or more selected from W, Cu, Sr, Mn, Y, Ti, Mg, Mo, B, Sn, Fe, Zn, Si, and Al, and 0.6 ≤ a2 < 1, 0 < b2 < 0.4, 0 < c2 < 0.4, 0 < d2 ≤ 0.01, 0 ≤ e2 ≤ 0.1, and a2 + b2 + c2 + d2 + e2 = 1.

13. The method of claim 12, wherein, The first firing is carried out for 2 hours to 10 hours.

14. The method of claim 12, wherein, The second firing is carried out for 2 hours to 10 hours.

15. The method of claim 12, wherein, The third firing is carried out for 2 hours to 10 hours.

16. The method according to claim 12, further comprising (C) finely pulverizing the fired product.

17. The method of claim 16, wherein, The fine grinding is carried out by vortex grinding.

18. The method of claim 17, wherein, The vortex pulverization is carried out at a pressure of 2.5 bar to 5 bar.

19. The method of claim 12, further comprising (C') mixing the calcined product with one or more selected from aluminum and tungsten raw materials, and then heat-treating the mixture to form a coating comprising one or more selected from Al and W on the calcined product.

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

21. A lithium secondary battery, comprising: The positive electrode as described in claim 20; negative electrode; A diaphragm placed between the positive electrode and the negative electrode; and Electrolytes.

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