Positive electrode active material and method for producing the same, positive electrode including the same, and lithium secondary battery

Abstract

To provide a positive electrode active material containing a lithium nickel composite oxide, which is economical, has high capacity, and long life characteristics, and has improved high voltage characteristics and high temperature characteristics, a method for manufacturing the same, and a positive electrode and a lithium secondary battery containing the same.SOLUTION: The present invention relates to a positive electrode active material including core particles containing a lithium-nickel composite oxide, and a coating layer located on the surface of the core particles and containing aluminum, yttrium, and tungsten, as well as a method for manufacturing the same and a positive electrode and lithium secondary battery containing the same.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material, a method for producing the same, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0002] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, high-capacity secondary batteries has been growing rapidly. As a result, research and development efforts to improve the performance of lithium secondary batteries have been actively conducted.

[0003] A lithium secondary battery is a battery that includes a cathode and an anode, each containing an active material capable of intercalating and deintercalating lithium ions, and an electrolyte. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are intercalated and deintercalated at the cathode and anode.

[0004] Various materials are being investigated as cathode active materials for realizing such lithium secondary batteries. Among these, lithium nickel oxide, lithium nickel manganese cobalt composite oxide, lithium nickel cobalt aluminum composite oxide, and lithium cobalt oxide are commonly used as cathode active materials. However, while demand for large-sized, high-capacity, and high-energy density lithium secondary batteries has recently surged, the supply of cathode active materials containing the rare metal cobalt is expected to be extremely short. In other words, because cobalt is expensive and its remaining reserves are limited, there is a need to develop cathode active materials that reduce the cobalt content or eliminate cobalt altogether. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a positive electrode active material containing a lithium nickel composite oxide, which is economical, has high capacity, and long life characteristics, and has improved high voltage characteristics and high temperature characteristics; a method for producing the same; and a positive electrode and a lithium secondary battery containing the same. [Means for solving the problem]

[0006] In one embodiment, a positive electrode active material is provided, comprising: a core particle comprising a lithium nickel-based composite oxide; and a coating layer located on a surface of the core particle, the coating layer comprising aluminum, yttrium, and tungsten.

[0007] In another embodiment, there is provided a method for manufacturing a cathode active material, the method including: mixing a nickel-based composite hydroxide and a lithium raw material; performing a first heat treatment to obtain a first composite oxide; introducing the first composite oxide into a solution in which an aluminum raw material and an yttrium raw material are mixed in an aqueous solvent; mixing and drying the first composite oxide; dry-mixing the dried product with a tungsten raw material; and performing a second heat treatment to obtain the cathode active material.

[0008] In another embodiment, a positive electrode is provided, comprising a current collector and a positive electrode active material layer disposed on the current collector, the positive electrode active material layer comprising the positive electrode active material described above.

[0009] In another embodiment, a lithium secondary battery is provided that includes the positive electrode, the negative electrode, and an electrolyte. [Effects of the Invention]

[0010] The positive electrode active material according to one embodiment maximizes capacity while minimizing production costs, ensures long-life characteristics, and improves high-voltage and high-temperature characteristics. A lithium secondary battery using the positive electrode active material can exhibit high initial charge / discharge capacity and efficiency even under high-voltage driving conditions, achieve long-life characteristics, and effectively suppress the problem of gas generation due to high-voltage and high-temperature driving. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 2] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 3] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 4] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 5] 1 is a scanning electron microscope (SEM) image of the surface of a positive electrode active material particle of Comparative Example 1. [Figure 6] 1 is a scanning electron microscope (SEM) image of the surface of a positive electrode active material particle of Comparative Example 1. [Figure 7] 10 is an SEM image of the surface of a positive electrode active material particle of Comparative Example 2. [Figure 8] 10 is an SEM image of the surface of a positive electrode active material particle of Comparative Example 2. [Figure 9] 10 is an SEM image of the surface of a positive electrode active material particle of Comparative Example 6. [Figure 10] 10 is an SEM image of the surface of a positive electrode active material particle of Comparative Example 6. [Figure 11] 1 is an SEM image of the surface of a positive electrode active material particle of Example 2. [Figure 12] 1 is an SEM image of the surface of a positive electrode active material particle of Example 2. [Figure 13] 10 is an SEM image of the surface of a positive electrode active material particle of Example 3. [Figure 14] 10 is an SEM image of the surface of a positive electrode active material particle of Example 3. [Figure 15] 1 is an image of the positive electrode active material produced in Example 4 taken in BSE mode using an SEM. [Figure 16] 10 shows the results of SEM-EDS analysis of the surface of a first positive electrode active material, which is a part of particles of the positive electrode active material prepared in Example 4. [Figure 17] 10 shows the results of SEM-EDS analysis of a cross section of a first positive electrode active material, which is a part of a particle of the positive electrode active material prepared in Example 4. [Figure 18] 10 shows the results of SEM-EDS analysis of the surface of a second positive electrode active material, which is a part of particles of a part of the positive electrode active material prepared in Example 4. [Figure 19] 10 shows the results of SEM-EDS analysis of a cross section of a second positive electrode active material, which is a part of a particle of a positive electrode active material prepared in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the present invention is given by way of example only, and the present invention is not limited thereto, but is defined only by the scope of the claims that follow.

[0013] Unless otherwise specified in this specification, when a layer, film, region, plate, or other part is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between.

[0014] Unless otherwise specified herein, the singular can also include the plural, and unless otherwise specified, "A or B" can mean "including A, including B, or including A and B."

[0015] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0016] Unless otherwise defined herein, particle size refers to the average particle size. Furthermore, particle size refers to the average particle size (D50), which refers to the diameter of particles with a cumulative volume of 50% in a particle size distribution. The average particle size (D50) can be measured by methods well known to those skilled in the art, such as using a particle size analyzer or a transmission electron microscope or scanning electron microscope. Alternatively, the average particle size (D50) can be measured using a measuring device that uses dynamic light scattering, and data analysis can be performed to count the number of particles in each particle size range, after which the average particle size (D50) can be calculated. Alternatively, the average particle size (D50) can be measured using a laser diffraction method. When measuring by the laser diffraction method, more specifically, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac's MT3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0017] It should be understood that the terms "comprise," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0018] Here, the term "layer" includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on a portion of the surface.

[0019] The term "metal" is understood to include general metals, transition metals, and metalloids (semimetals).

[0020] positive electrode active material In one embodiment, a positive electrode active material is provided, comprising: a core particle comprising a lithium nickel-based composite oxide; and a coating layer located on a surface of the core particle, the coating layer comprising aluminum, yttrium, and tungsten.

[0021] Recently, LiCoO2 (LCO), LiNi x Co y Mn z O2(NCM), LiNi x Co y Al z However, as the price of cobalt is rising sharply worldwide, there is a demand for the development of positive electrode active materials that reduce the cobalt content or do not contain cobalt at all.

[0022] Among these, cathode active materials with an olivine crystal structure, such as lithium iron phosphate (LFP), lithium manganese phosphate (LMP), and lithium manganese iron phosphate (LMFP), or a spinel crystal structure, such as lithium manganese oxide (LMO), have limitations in achieving high capacity due to the small amount of lithium that can be utilized within the structure.

[0023] Layered nickel-manganese cathode active materials are suitable for high-capacity batteries because they can increase the amount of lithium in their structure, resulting in excellent capacity and efficiency. However, the removal of cobalt, which plays a key role in the layered structure, reduces structural stability and increases resistance, making it difficult to ensure long life. Furthermore, the removal of cobalt accelerates side reactions between the cathode active material and electrolyte under high voltage and high temperature conditions, increasing gas generation and reducing life.

[0024] Therefore, in one embodiment, a cathode active material is proposed in which a lithium-nickel composite oxide is used as a core particle and a coating layer containing aluminum, yttrium, and tungsten is formed. This allows the cobalt content required for the core particle to be reduced or eliminated to ensure structural stability, thereby ensuring price competitiveness. Furthermore, by including aluminum, yttrium, and tungsten in the coating layer, battery capacity and efficiency can be maximized, and long-life characteristics can be achieved by reducing gas generation even under high-voltage and high-temperature conditions.

[0025] core particle The core particles include a lithium nickel-based composite oxide. For example, the lithium nickel-based composite oxide may be represented by the following Chemical Formula 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0026] In the formula 1, 0.9≦a1≦1.8, 0.3≦x1≦0.98, 0≦y1≦0.7, 0≦z1≦0.7, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1; M 1 and M 2 are each independently Al, B, Ba, Ca, Ce, Co, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, Y, W, Zr or a combination thereof, and X is F, P, S or a combination thereof.

[0027] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.5, or 0.9 ≤ a1 ≤ 1.2 may hold. Also, 0.35 ≤ x1 ≤ 0.95, 0.4 ≤ x1 ≤ 0.9, 0.45 ≤ x1 ≤ 0.85, 0.5 ≤ x1 ≤ 0.8, or 0.69 ≤ x1 ≤ 0.79 may hold, 0.1 ≤ y1 ≤ 0.65, 0.1 ≤ y1 ≤ 0.60, 0.1 ≤ y1 ≤ 0.55, 0.15 ≤ y1 ≤ 0.5, or 0.2 ≤ y1 ≤ 0.4 may hold, and 0.01 < z1 ≤ 0.5, 0.01 < z1 ≤ 0.3, or 0.01 < z1 ≤ 0.1 etc. may hold.

[0028] In one embodiment, the lithium nickel-based composite oxide may be a lithium nickel-manganese-based composite oxide or a lithium nickel-manganese-aluminum-based composite oxide. Also, the lithium nickel-based composite oxide may have a layered structure.

[0029] For example, the lithium nickel-manganese-based composite oxide may be represented by the following Chemical Formula 2. [Chemical Formula 2] Li a2 Ni x2 Mn y2 M 1 z2 M 2 w2 O 2-b2 X b2

[0030] In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.6 ≤ x2 ≤ 0.8, 0.1 ≤ y2 ≤ 0.39, 0.01 < z2 ≤ 0.03, 0 ≤ w2 ≤ 0.29, 0.9 ≤ x2 + y2 + z2 + w2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, where M 1 and M 2 are each independently Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, Y, W, Zr, or a combination thereof, and X is F, P, S, or a combination thereof.

[0031] In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.5, or 0.9 ≤ a2 ≤ 1.2 may hold. Also, 0.6 ≤ x2 ≤ 0.79, 0.6 ≤ x2 ≤ 0.78, 0.6 ≤ x2 ≤ 0.75, 0.65 ≤ x2 ≤ 0.8, or 0.7 ≤ x2 ≤ 0.79 may hold, 0.1 ≤ y2 ≤ 0.35, 0.1 ≤ y2 ≤ 0.30, 0.1 ≤ y2 ≤ 0.29, 0.15 ≤ y2 ≤ 0.39, or 0.2 ≤ y2 ≤ 0.3 may hold, 0.01 < z2 ≤ 0.025, 0.01 < z2 ≤ 0.02, or 0.01 < z2 ≤ 0.019 may hold, 0 ≤ w2 ≤ 0.28, 0 ≤ w2 ≤ 0.27, 0 ≤ w2 ≤ 0.26, 0 ≤ w2 ≤ 0.25, 0 ≤ w2 ≤ 0.24, 0 ≤ w2 ≤ 0.23, 0 ≤ w2 ≤ 0.22, 0 ≤ w2 ≤ 0.21, 0 ≤ w2 ≤ 0.2, 0 ≤ w2 ≤ 0.15, 0 ≤ w2 ≤ 0.1, or 0 ≤ w2 ≤ 0.09 etc. may hold.

[0032] For example, the lithium nickel-manganese-aluminum composite oxide may be represented by the following Chemical Formula 3. [Chemical Formula 3] Li a3 Ni x3 Mn y3 Al z3 M 1 w3 O 2-b3 X b3

[0033] In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.8, 0.6 ≤ x3 ≤ 0.8, 0.1 ≤ y3 ≤ 0.39, 0.01 < z3 ≤ 0.03, 0 ≤ w3 ≤ 0.29, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, and M 1 is Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, Y, W, Zr, or a combination thereof, and X is F, P, S, or a combination thereof.

[0034] In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.5 or 0.9 ≤ a3 ≤ 1.2 may hold. Also, 0.6 ≤ x3 ≤ 0.79, 0.6 ≤ x3 ≤ 0.78, 0.6 ≤ x3 ≤ 0.75, 0.65 ≤ x3 ≤ 0.8, or 0.7 ≤ x3 ≤ 0.79 may hold, 0.1 ≤ y3 ≤ 0.35, 0.1 ≤ y3 ≤ 0.30, 0.1 ≤ y3 ≤ 0.29, 0.15 ≤ y3 ≤ 0.39, or 0.2 ≤ y3 ≤ 0.3 may hold, 0.01 < z3 ≤ 0.025, 0.01 < z3 ≤ 0.02, or 0.01 < z3 ≤ 0.019 may hold, and 0 ≤ w3 ≤ 0.28, 0 ≤ w3 ≤ 0.27, 0 ≤ w3 ≤ 0.26, 0 ≤ w3 ≤ 0.25, 0 ≤ w3 ≤ 0.24, 0 ≤ w3 ≤ 0.23, 0 ≤ w3 ≤ 0.22, 0 ≤ w3 ≤ 0.21, 0 ≤ w3 ≤ 0.2, 0 ≤ w3 ≤ 0.15, 0 ≤ w3 ≤ 0.1, or 0 ≤ w3 ≤ 0.09 etc. may hold.

[0035] The nickel content can satisfy 60 mol% or more with respect to 100 mol% of the total metals excluding lithium in the positive electrode active material. Nickel is contained in the core particles but may partially move to the coating layer during the coating process, and thus the nickel content may mean the nickel content contained in the entire positive electrode active material. The nickel content can be, for example, 60 mol% - 80 mol%, 65 mol% - 80 mol%, 70 mol% - 80 mol%, 60 mol% - 79 mol%, 60 mol% - 78 mol%, or 60 mol% - 75 mol% etc. with respect to 100 mol% of the total metals excluding lithium in the positive electrode active material. When the nickel content satisfies the above range, high capacity can be achieved, and even if the cobalt content is reduced, the structural safety can be enhanced.

[0036] The manganese content may be, for example, 10 mol% to 39 mol%, 10 mol% to 35 mol%, 10 mol% to 30 mol%, 10 mol% to 29 mol%, 15 mol% to 39 mol%, 20 mol% to 39 mol%, or 20 mol% to 30%, based on 100 mol% of all metals in the positive electrode active material (excluding lithium). Manganese is contained in the core particles, but some of it may migrate to the coating layer during the coating process. Therefore, the manganese content may refer to the manganese content contained in the entire positive electrode active material. When the manganese content satisfies this range, the positive electrode active material can achieve high capacity while improving structural stability.

[0037] For example, the aluminum content of the core particles may be 0.1 mol% or more, 0.5 mol% or more, or 1 mol% or more, and 3 mol% or less, 2 mol% or less, or 1.9 mol% or less, based on 100 mol% of all metals excluding lithium in the positive electrode active material. Here, the aluminum content refers to the content of aluminum present in the core particles. When the aluminum content of the core particles satisfies this range, a stable layered structure can be maintained even if cobalt is excluded from the core particles, preventing the problem of structural collapse during charge and discharge, and achieving long-life characteristics of the positive electrode active material.

[0038] According to one embodiment, the aluminum concentration within the core particle may be relatively uniform. This means that there is an aluminum concentration gradient from the center to the surface within the core particle, or that the aluminum concentration is neither higher nor lower at the outside than at the inside of the core particle, and that the aluminum is uniformly dispersed within the core particle. This can be said to be a structure obtained by synthesizing a composite oxide using a nickel-manganese-aluminum hydroxide as a precursor without additionally doping aluminum during the core particle synthesis process. The core particle may be in the form of a secondary particle formed by agglomeration of multiple primary particles, but the aluminum content within the primary particle can also be said to be the same or similar regardless of the position of the primary particle. In other words, if a primary particle is selected at any position in the cross section of the secondary particle and the aluminum content is measured within the primary particle rather than at the interface, the aluminum content can be expressed as the same / similar / uniform regardless of the position of the primary particle, i.e., whether the primary particle is near the center or the surface of the secondary particle. In this structure, a stable layered structure can be maintained even when cobalt is absent or present in only a small amount, and aluminum by-products and aluminum aggregates are not generated, so the capacity, efficiency, and life characteristics of the positive electrode active material can be improved simultaneously.

[0039] The lithium nickel-manganese-aluminum composite oxide of the core particles may be, for example, a cobalt-free compound that does not contain cobalt or contains a very small amount of cobalt.

[0040] The core particle may be in the form of a secondary particle formed by agglomeration of multiple primary particles. The secondary particles may be spherical, ellipsoidal, polyhedral, or irregular in shape, while the primary particles may be spherical, ellipsoidal, plate-like, or a combination thereof.

[0041] The core particles are susceptible to chemical attack from components in the electrolyte when the battery is operated under high voltage or high temperature conditions, and therefore, there is a possibility that side reactions with the electrolyte may occur frequently, resulting in a large amount of gas generation and a decrease in battery life and safety. However, this problem can be solved by introducing a coating layer according to one embodiment described below.

[0042] Coating layer The positive electrode active material includes a coating layer located on the surface of the core particle and containing aluminum, yttrium, and tungsten. In one embodiment, the coating layer contains all of aluminum, yttrium, and tungsten, which can significantly reduce gas generation under high voltage or high temperature operating conditions compared to when only one or two of these elements are contained.

[0043] The coating layer according to one embodiment may be in the form of a film that continuously surrounds the surface of the core particle, or may be in the form of islands.

[0044] For example, the coating layer may be in the form of a film that continuously surrounds the surface of the core particle. The film-like coating layer may be in the form of a shell that surrounds the entire surface of the core particle, which is different from a structure in which only a portion of the surface of the core particle is partially coated. While the coating layer is formed to completely surround the surface of the core particle, it may be very thin and relatively uniform in thickness, which may improve the structural stability of the cathode active material without increasing resistance or decreasing capacity. Furthermore, side reactions with the electrolyte may be effectively suppressed, reducing gas generation under high-voltage and high-temperature conditions and achieving long-life characteristics.

[0045] For example, the aluminum content of the coating layer may be 0.1 mol% to 2.5 mol%, e.g., 0.2 mol% to 2.3 mol%, 0.3 mol% to 2.0 mol%, 0.5 mol% to 2.0 mol%, 0.8 mol% to 2.0 mol%, or 0.8 mol% to 1.3 mol%, based on 100 mol% of the total metals (excluding lithium) in the positive electrode active material. This refers to the aluminum content of the coating layer, separate from the aluminum contained in the core particles. The aluminum content of the coating layer can be measured, for example, by SEM-EDS analysis of the surface or cross-section of the positive electrode active material. When the aluminum content of the coating layer satisfies the above range, a uniform and thin coating layer can be formed, the resistance of the positive electrode active material is not increased, and side reactions with the electrolyte are effectively suppressed, thereby improving the life characteristics of lithium secondary batteries under high-voltage and high-temperature conditions.

[0046] For example, the yttrium content of the coating layer may be 0.05 mol% to 1.5 mol%, e.g., 0.1 mol% to 1.5 mol%, 0.1 mol% to 1.3 mol%, 0.1 mol% to 1.2 mol%, 0.1 mol% to 1.0 mol%, or 0.1 mol% to 0.6 mol%, based on 100 mol% of all metals excluding lithium in the positive electrode active material. When the yttrium content of the coating layer satisfies this range, the positive electrode active material forms a good coating layer without a decrease in capacity or an increase in resistance, effectively suppressing side reactions with the electrolyte and effectively reducing gas generation under high voltage and high temperature conditions.

[0047] For example, the tungsten content of the coating layer may be 0.01 mol% to 1.5 mol%, e.g., 0.02 mol% to 1.3 mol%, 0.03 mol% to 1.2 mol%, 0.04 mol% to 1.0 mol%, 0.05 mol% to 0.3 mol%, or 0.1 mol% to 0.2 mol%, based on 100 mol% of all metals (excluding lithium) in the positive electrode active material. When the tungsten content of the coating layer satisfies this range, the structural stability of the positive electrode active material can be further improved and side reactions with the electrolyte can be effectively suppressed. This can maximize the reduction in gas generation in lithium secondary batteries under high-voltage and high-temperature conditions.

[0048] According to one embodiment, the positive electrode active material is obtained by heat treatment at a high temperature of 800°C or higher in an oxygen atmosphere during manufacturing, and therefore, aluminum, yttrium, and tungsten may be present in the form of oxides in the coating layer. For example, the coating layer may include an oxide of a metal selected from aluminum, yttrium, tungsten, or a combination thereof. In one embodiment, the coating layer may include aluminum oxide, yttrium oxide, and tungsten oxide, and / or a composite oxide containing two or more elements selected from aluminum, yttrium, and tungsten. For example, the metal oxide in the coating layer may further include lithium. In one embodiment, the aluminum in the coating layer may be present as aluminum oxide (e.g., Al2O3) or lithium aluminum oxide (e.g., LiAlO2, LiAl5O8, Li5AlO4), the yttrium may be present as yttrium oxide (Y2O3) or lithium yttrium oxide (e.g., LiYO2), and the tungsten may be present as tungsten oxide (WO3) or lithium tungsten oxide (e.g., Li2WO4). This may be advantageous for improving the life characteristics and reducing gas generation of lithium secondary batteries under high-voltage and high-temperature conditions. The presence of aluminum, yttrium, and tungsten in the coating layer in the form of oxides can be confirmed by elemental analysis using EDS analysis or SEM-EDS analysis, or by crystal structure analysis using Fourier transformation after measurement using HR-TEM.

[0049] As an example, the yttrium content (C Y ) to the tungsten content (C W ) molar ratio (C W / C Y) may be 1.0 or less, for example, 0.01 to 1.0, 0.05 to 1.0, 0.1 to 1.0, or 0.25 to 1.0. In this case, the positive electrode active material forms a good coating layer without a decrease in capacity or an increase in resistance, effectively suppressing side reactions with the electrolyte and effectively reducing the amount of gas generation under high voltage and high temperature conditions.

[0050] In another example, the aluminum content (C Al ) to the tungsten content (C W ) molar ratio (C W / C Al ) may be 0.5 or less, for example, 0.01 to 0.5, 0.03 to 0.5, or 0.05 to 0.5. In this case, the positive electrode active material can ensure structural stability while forming a good coating layer without decreasing capacity or increasing resistance, effectively suppressing side reactions with the electrolyte, and effectively reducing the amount of gas generation under high voltage and high temperature conditions.

[0051] The thickness of the coating layer may be 30 nm to 1 μm, for example, 50 nm to 1 μm, 80 nm to 800 nm, or 100 nm to 500 nm. When the coating layer satisfies this thickness range, the coating can improve the structural stability of the positive electrode active material and effectively suppress side reactions with the electrolyte without increasing resistance or decreasing capacity. The thickness of the coating layer can be measured, for example, by TOF-SIMS, XPS, or EDS analysis, and the thickness range of the coating layer can be measured by SEM-EDS or TEM-EDS line profile.

[0052] In one embodiment, the coating layer may contain a mixture of aluminum, yttrium, and tungsten.

[0053] According to one embodiment, the aluminum in the coating layer may be present in the form of a continuous film or in the form of islands.

[0054] According to one embodiment, one or more of aluminum, yttrium, and tungsten may be present in an island shape in the coating layer, for example, one or more of yttrium and tungsten may be present in an island shape in the coating layer, which may improve the structural stability of the positive electrode active material, reduce gas generation even under high voltage and high temperature conditions, and effectively achieve long-life characteristics.

[0055] For example, in the coating layer, the aluminum may be present in the form of a continuous film or in the form of islands, and one or more of yttrium and tungsten may be present in the form of islands, but is not particularly limited thereto.

[0056] In one embodiment, the island shape may have a thickness of 10 nm to 500 nm. When this thickness is satisfied, the structural stability of the positive electrode active material may be improved, the amount of gas generation may be reduced even under high voltage and high temperature conditions, and long-life characteristics may be effectively achieved. Here, the size of the island shape may be measured, for example, through component analysis using SEM-EDS on a cross section of the positive electrode active material.

[0057] In another embodiment, the positive electrode active material may be a first positive electrode active material having a prominent yttrium coating in the coating layer, and a second positive electrode active material having a prominent tungsten coating. When this is satisfied, the effects of reducing gas generation and achieving long-life characteristics can be harmoniously achieved even under high voltage and high temperature conditions.

[0058] For example, the positive electrode active material may include a first positive electrode active material in which yttrium is present in an island shape, a second positive electrode active material in which tungsten is present in an island shape, or a combination thereof. For example, the positive electrode active material may include a first positive electrode active material in which yttrium is present in an island shape and a second positive electrode active material in which tungsten is present in an island shape, and the size of the yttrium-containing islands in the first positive electrode active material may be smaller than the size of the tungsten-containing islands in the second positive electrode active material. When this is satisfied, the effects of reducing gas generation and achieving long-life characteristics can be maximized even under high-voltage and high-temperature conditions.

[0059] Meanwhile, the coating layer may further contain nickel, manganese, or a combination thereof in addition to aluminum, yttrium, and tungsten. Nickel and manganese may be contained in the core particles and introduced during the formation of the coating layer, and their contents are not particularly limited. According to one embodiment, the coating layer essentially contains aluminum, yttrium, and tungsten, and selectively contains nickel and manganese. The coating layer is formed to a thin and uniform thickness, thereby improving the high-voltage characteristics and life characteristics of the positive electrode active material.

[0060] Grain boundary coating section During the formation of the coating layer, aluminum may diffuse into the core particles. To this end, a positive electrode active material according to an embodiment may further include a grain boundary coating region containing aluminum located on the surface of the primary particle within the secondary particle. Here, the term "secondary particle" refers to the core particle, and the "interior of the secondary particle" may refer to the entire interior of the secondary particle excluding the surface, or may refer to the region extending from the surface of the secondary particle toward the center of the secondary particle, extending up to approximately 60% of the radius. The grain boundary coating region is a concept distinct from the coating layer on the surface of the core particle, and refers to a coating region formed on the surface of the primary particle located within the core particle. The presence of the grain boundary coating region can be confirmed by SEM-EDS analysis of a cross section of the positive electrode active material. The formation of the aluminum grain boundary coating region may further stabilize the structure of the positive electrode active material, thereby improving its lifespan.

[0061] The aluminum content in the grain boundary coating portion is not particularly limited, and as an example, the aluminum content in the grain boundary coating portion may be less than the aluminum content in the coating layer.

[0062] In addition to aluminum, the grain boundary coating may further contain nickel, manganese, or a combination thereof.

[0063] Internal pores In one embodiment, the core particles of the positive electrode active material may have pores therein. Therefore, during the formation of the coating layer, tungsten may diffuse into the core particles, thereby further including tungsten in the pores of the core particles.

[0064] The average particle size (D 50) is not particularly limited, and may be, for example, 10 μm to 18 μm, 11 μm to 16 μm, or 12 μm to 15 μm. The average particle size is determined by measuring the size (diameter or length of the major axis) of 20 or more particles randomly selected from a scanning electron microscope image of the positive electrode active material to obtain a particle size distribution, and then determining the diameter (D) of the particles whose cumulative volume is 50% by volume from the particle size distribution. 50 When the average particle size of the positive electrode active material satisfies this range, high capacity and long life can be achieved, which may be advantageous for forming a coating layer according to an embodiment.

[0065] In the positive electrode active material according to an embodiment, the cobalt content may be, for example, 0.01 mol% or less, 0.005 mol% or less, or 0.001 mol% or less, for example, 0 mol% to 0.01 mol%, based on 100 mol% of all metals excluding lithium. The positive electrode active material according to an embodiment may be, for example, a cobalt-free positive electrode active material.

[0066] In addition, the cathode active material according to an embodiment may be characterized as being sodium-free. Although sodium ions are typically used in the manufacturing process of a cathode active material, the manufacturing method described below allows core particles with a stable structure and a coating layer with a uniform thickness to be formed without using sodium ions.

[0067] Method for producing positive electrode active material In one embodiment, a method for manufacturing a cathode active material is provided, the method comprising: mixing a nickel-based composite hydroxide and a lithium source material, performing a first heat treatment to obtain a first composite oxide, adding the first composite oxide to a solution in which an aluminum source material and an yttrium source material are mixed in an aqueous solvent, mixing and drying the first composite oxide, dry-mixing the dried product with a tungsten source material, and performing a second heat treatment to obtain a cathode active material. The cathode active material described above can be manufactured through the method.

[0068] The nickel-based composite hydroxide is a precursor of core particles and may be in the form of secondary particles in which a plurality of primary particles are aggregated. For example, the nickel-based composite hydroxide may be represented by the following Chemical Formula 11. [Chemical Formula 11] Ni x11 M 1 y11 M 2 z11 (OH)2

[0069] In Chemical Formula 11, 0.3 ≦ x11 ≦ 0.98, 0 ≦ y11 ≦ 0.7, 0 ≦ z11 ≦ 0.7, and 0.9 ≦ x11 + y11 + z11 ≦ 1.1, and M 1 and M 2 are each independently Al, B, Ba, Ca, Ce, Co, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, Y, W, Zr, or a combination thereof.

[0070] In Chemical Formula 11, 0.35 ≦ x11 ≦ 0.95, 0.4 ≦ x11 ≦ 0.9, 0.45 ≦ x11 ≦ 0.85, 0.5 ≦ x11 ≦ 0.8, or 0.69 ≦ x11 ≦ 0.79 may be satisfied, 0.1 ≦ y11 ≦ 0.65, 0.1 ≦ y11 ≦ 0.60, 0.1 ≦ y11 ≦ 0.55, 0.15 ≦ y11 ≦ 0.5, or 0.2 ≦ y11 ≦ 0.4 may be satisfied, 0.01 < z11 ≦ 0.5, 0.01 < z11 ≦ 0.3, or 0.01 < z11 ≦ 0.1, etc. may be satisfied.

[0071] In one embodiment, the nickel-based composite hydroxide may be a nickel-manganese-based composite hydroxide or a nickel-manganese-aluminum-based composite hydroxide. For example, the nickel-based composite hydroxide may contain no cobalt or contain a very small amount of cobalt, and may be, for example, a cobalt-free nickel-manganese-aluminum-based composite hydroxide. The nickel-based composite hydroxide can be produced by a general coprecipitation method.

[0072] In one embodiment, a method for manufacturing a positive electrode active material does not require additional doping with aluminum during the preparation of core particles, but instead uses an aluminum raw material during the preparation of a precursor, thereby enabling the use of a nickel-manganese-aluminum composite hydroxide as a precursor in which aluminum is uniformly dispersed within the structure. Using such a precursor allows the manufacture of a positive electrode active material that stably maintains its layered structure during repeated charge and discharge cycles, even without cobalt. Furthermore, the absence of aluminum by-products or aluminum aggregates can improve the capacity, efficiency, and lifespan characteristics of the positive electrode active material.

[0073] In one embodiment, the nickel content in the nickel-based composite hydroxide is 60 mol% or more relative to 100 mol% of the total metals, and may be, for example, 60 mol% to 80 mol%, 65 mol% to 80 mol%, 70 mol% to 80 mol%, 60 mol% to 79 mol%, 60 mol% to 78 mol%, or 60 mol% to 75 mol%, etc. When the nickel content satisfies the above range, high capacity can be achieved, and structural safety can be improved even when the cobalt content is reduced.

[0074] For example, the manganese content in the nickel-manganese composite hydroxide (or nickel-manganese-aluminum composite hydroxide) may be 10 mol% to 39 mol%, 10 mol% to 35 mol%, 10 mol% to 30 mol%, 10 mol% to 29 mol%, 15 mol% to 39 mol%, 20 mol% to 39 mol%, 20 mol% to 30%, etc., relative to 100 mol% of the total metals. Furthermore, the aluminum content in the nickel-manganese composite hydroxide (or nickel-manganese-aluminum composite hydroxide) may be 0.1 mol% or more, 0.5 mol% or more, or 1 mol% or more, for example, 1 mol% to 3 mol%, 1 mol% to 2.5 mol%, 1 mol% to 2 mol%, or 1 mol% to 1.9 mol%, relative to 100 mol% of the total metals. When the manganese and aluminum contents of the composite hydroxide are within the above ranges, the structural stability of the positive electrode active material can be improved while achieving high capacity, and the production cost can be reduced, resulting in improved economic efficiency.

[0075] According to one embodiment, the cobalt content in the nickel-manganese-based composite hydroxide (or nickel-manganese-aluminum-based composite hydroxide) may be 0.01 mol% or less, 0.005 mol% or less, or 0.001 mol% or less, relative to 100 mol% of the total metals. Such a nickel-manganese-aluminum-based composite hydroxide is economical because it can avoid the increase in unit price due to cobalt, and it can be said to maximize capacity and improve structural stability.

[0076] For example, the nickel-based composite hydroxide may be represented by the following Chemical Formula 12: [Chemical formula 12] Ni x12 Mn y12 M 1 z12 M 2 w12 (OH)2

[0077] In chemical formula 12, 0.6≦x12≦0.8, 0.1≦y12≦0.39, 0.01 <z12≦0.03、0≦w12≦0.29、および0.9≦x12+y12+z12+w12≦1.1であり、M 1 and M 2 are each independently Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, Y, W, Zr, or a combination thereof, and X is F, P, S, or a combination thereof.

[0078] In Chemical Formula 12, 0.6 ≤ x12 ≤ 0.79, 0.6 ≤ x12 ≤ 0.78, 0.6 ≤ x12 ≤ 0.75, 0.65 ≤ x12 ≤ 0.8, or 0.7 ≤ x12 ≤ 0.79 can hold; 0.1 ≤ y12 ≤ 0.35, 0.1 ≤ y12 ≤ 0.30, 0.1 ≤ y12 ≤ 0.29, 0.15 ≤ y12 ≤ 0.39, or 0.2 ≤ y12 ≤ 0.3 can hold; 0.01 < z12 ≤ 0.025, 0.01 < z12 ≤ 0.02, or 0.01 < z12 ≤ 0.019 can hold; 0 ≤ w12 ≤ 0.28, 0 ≤ w12 ≤ 0.27, 0 ≤ w12 ≤ 0.26, 0 ≤ w12 ≤ 0.25, 0 ≤ w12 ≤ 0.24, 0 ≤ w12 ≤ 0.23, 0 ≤ w12 ≤ 0.22, 0 ≤ w12 ≤ 0.21, 0 ≤ w12 ≤ 0.2, 0 ≤ w12 ≤ 0.15, 0 ≤ w12 ≤ 0.1, or 0 ≤ w12 ≤ 0.09 etc. can hold.

[0079] For example, the nickel-based composite hydroxide may be represented by the following Chemical Formula 13. [Chemical Formula 13] Ni x13 Mn y13 Al z13 M 1 w13 (OH)2

[0080] In Chemical Formula 13, 0.6 ≤ x13 ≤ 0.8, 0.1 ≤ y13 ≤ 0.39, 0.01 < z13 ≤ 0.03, 0 ≤ w13 ≤ 0.29, and 0.9 ≤ x13 + y13 + z13 + w13 ≤ 1.1, and M 1 is Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, Y, W, Zr, or a combination thereof.

[0081] In Chemical Formula 13, 0.6 ≦ x13 ≦ 0.79, 0.6 ≦ x13 ≦ 0.78, 0.6 ≦ x13 ≦ 0.75, 0.65 ≦ x13 ≦ 0.8, or 0.7 ≦ x13 ≦ 0.79 can be satisfied; 0.1 ≦ y13 ≦ 0.35, 0.1 ≦ y13 ≦ 0.30, 0.1 ≦ y13 ≦ 0.29, 0.15 ≦ y13 ≦ 0.39, or 0.2 ≦ y13 ≦ 0.3 can be satisfied; 0.01 < z13 ≦ 0.025, 0.01 < z13 ≦ 0.02, or 0.01 < z13 ≦ 0.019 can be satisfied; 0 ≦ w13 ≦ 0.28, 0 ≦ w13 ≦ 0.27, 0 ≦ w13 ≦ 0.26, 0 ≦ w13 ≦ 0.25, 0 ≦ w13 ≦ 0.24, 0 ≦ w13 ≦ 0.23, 0 ≦ w13 ≦ 0.22, 0 ≦ w13 ≦ 0.21, 0 ≦ w13 ≦ 0.2, 0 ≦ w13 ≦ 0.15, 0 ≦ w13 ≦ 0.1, or 0 ≦ w13 ≦ 0.09 etc. can be satisfied.

[0082] For example, the nickel-based composite hydroxide is in a particulate form, and the average particle size (D 50 ) thereof can be 10 μm to 18 μm, 11 μm to 16 μm, or 12 μm to 15 μm.

[0083] In one embodiment, the lithium raw material can include, for example, lithium hydroxide hydrate, anhydrous lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, or a combination thereof.

[0084] For example, the nickel-based composite hydroxide and the lithium raw material can be mixed at a molar ratio of 1:0.9 to 1:1.8, and can be mixed at a molar ratio of, for example, 1:0.9 to 1:1.5 or 1:0.9 to 1:1.2.

[0085] As an example, the first heat treatment can be carried out in an oxygen atmosphere, and can be carried out, for example, in a temperature range of 750 °C to 950 °C, or 780 °C to 900 °C, or 810 °C to 89 °C, and can be carried out for 2 hours to 20 hours, 4 hours to 12 hours, or 8 hours to 12 hours.

[0086] A first composite oxide can be obtained through the first heat treatment. The first composite oxide can be a lithium-nickel composite oxide, a lithium-nickel-manganese composite oxide, or a lithium-nickel-manganese-aluminum composite oxide. The obtained first composite oxide can contain at least 60 mol% of nickel, for example, 60 mol% to 80 mol%, based on 100 mol% of all metals excluding lithium, and can contain no cobalt or a very small amount of cobalt of 0.01 mol% or less. If the first composite oxide is a cobalt-free lithium-nickel-manganese composite oxide or nickel-manganese-aluminum composite oxide, the residual lithium content on the particle surface can be significantly different from that of nickel-based oxides of other compositions, such as lithium-nickel-cobalt-manganese composite oxide and lithium-nickel-cobalt-aluminum composite oxide, and various surface properties can be different. Furthermore, it can be possible to form a coating layer with a more uniform film morphology than existing coating methods. According to one embodiment, a very thin and uniform coating layer can be formed on the surface of a lithium nickel-manganese based composite oxide (or lithium nickel-manganese-aluminum based composite oxide) having an extremely small amount of cobalt and a nickel content of 60 mol % or more, thereby improving high voltage and high temperature characteristics.

[0087] A solution of aluminum raw material and yttrium raw material mixed in an aqueous solvent is prepared, and the first composite oxide is added to the solution, mixed, and then dried. This method is called a wet coating method, and it is possible to form a coating layer containing aluminum and yttrium as active ingredients.

[0088] For example, the aqueous solvent may include distilled water, an alcohol-based solvent, or a combination thereof. The aluminum source may include, for example, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum hydroxide, or a combination thereof, and aluminum sulfate may be used as the aluminum source. The yttrium source may include, for example, yttrium nitrate, yttrium sulfate, yttrium carbonate, yttrium hydroxide, or a combination thereof. If this requirement is met, it may be advantageous to form a coating layer with a uniform thickness on the surface of the lithium-nickel composite oxide particles, which are the first composite oxide.

[0089] The aluminum raw material is a raw material for forming the coating layer, and the aluminum content in the aluminum raw material can be designed to be 0.1 mol% to 2.5 mol% relative to 100 mol% of the total metals excluding lithium in the final cathode active material, for example, 0.2 mol% to 2.3 mol%, 0.3 mol% to 2.0 mol%, 0.5 mol% to 2.0 mol%, 0.8 mol% to 2.0 mol%, or 0.8 mol% to 1.3 mol%. Similarly, the yttrium raw material is a raw material for forming the coating layer, and the yttrium content in the yttrium raw material can be designed to be 0.05 mol% to 1.5 mol% relative to 100 mol% of the total metals excluding lithium in the final cathode active material, for example, 0.1 mol% to 1.5 mol%, 0.1 mol% to 1.3 mol%, 0.1 mol% to 1.2 mol%, 0.1 mol% to 1.0 mol%, or 0.1 mol% to 0.6 mol%. By designing the content of each of the coating materials within the above ranges, it is possible to form a coating layer having a uniform thickness of tens to hundreds of nanometers, thereby reducing the amount of gas generation in the lithium secondary battery under high voltage or high temperature operating conditions and improving the high capacity and long life characteristics.

[0090] The solution obtained by mixing the aluminum raw material and the yttrium raw material in an aqueous solvent may have a pH of 1.5 to 3.5, for example, 2.0 to 3.4, 2.5 to 3.3, 2.7 to 3.3, or 2.9 to 3.2. The first composite oxide may be added to the solution containing the aluminum raw material and the yttrium raw material and mixed for approximately 5 to 80 minutes, 5 to 60 minutes, or 5 to 40 minutes, and the mixing may be performed with stirring. The pH of the mixed solution after stirring may be 4.5 to 8.5, for example, 5.0 to 8.0, 5.5 to 7.5, or 6.0 to 7.0. Satisfying these conditions may be advantageous for forming a coating layer of uniform thickness.

[0091] Drying after the mixing process can be understood as a process of removing the solvent, and can be carried out at, for example, 40°C to 300°C, 100°C to 220°C, or 150°C to 200°C.

[0092] The method further includes dry-mixing the dried product with a tungsten raw material and then performing a second heat treatment. The second heat treatment may form a coating layer containing aluminum, yttrium, and tungsten as active ingredients on the positive electrode active material, thereby obtaining a positive electrode active material according to an embodiment.

[0093] For example, the tungsten raw material is a raw material for forming a coating layer containing tungsten as an active ingredient, and the tungsten content in the tungsten raw material is designed to be 0.01 mol% to 1.5 mol% relative to 100 mol% of the total metals excluding lithium in the final cathode active material, e.g., 0.02 mol% to 1.3 mol%, 0.03 mol% to 1.2 mol%, 0.04 mol% to 1.0 mol%, 0.05 mol% to 0.3 mol%, or 0.1 mol% to 0.2 mol%. By designing the tungsten raw material content within these ranges, a coating layer having a thin and uniform thickness on the order of tens to hundreds of nanometers can be formed, reducing the amount of gas generation in lithium secondary batteries under high-voltage or high-temperature operating conditions and improving high-capacity and long-life characteristics.

[0094] In one embodiment, the amount of yttrium source and tungsten source added during the manufacturing process is adjusted to the yttrium content (C Y ) to the tungsten content (C W ) molar ratio (C W / C Y ) can be designed to be 1.0 or less, for example, 0.01 to 1.0, 0.05 to 1.0, 0.1 to 1.0, or 0.25 to 1.0. When this is satisfied, the amount of gas generated by the lithium secondary battery under high-voltage or high-temperature operating conditions can be reduced, and high capacity and long-life characteristics can be improved.

[0095] For example, in the manufacturing process, the amount of aluminum raw material and tungsten raw material added is determined based on the aluminum content (C Al ) to the tungsten content (C W ) molar ratio (C W / C Al ) can be designed to be 0.5 or less, for example, 0.01 to 0.5, 0.03 to 0.5, or 0.05 to 0.5. When this is satisfied, the positive electrode active material can ensure structural stability while forming a good coating layer without a decrease in capacity or an increase in resistance, effectively suppressing side reactions with the electrolyte and effectively reducing the amount of gas generation under high voltage and high temperature conditions.

[0096] The tungsten source may include, for example, tungsten oxide, tungsten sulfide, sodium tungstate, ammonium tungstate, or a combination thereof, which allows for the effective formation of a tungsten-containing coating layer having a uniform thickness on the surface of the lithium nickel-based composite oxide core particles.

[0097] The positive electrode active material can be obtained through a second heat treatment, which may be a process for forming a coating layer containing aluminum, yttrium, and tungsten as active ingredients on the surface of the lithium-nickel composite oxide particles (core particles). For example, the second heat treatment may be performed in an oxygen atmosphere at 700°C to 900°C, e.g., 730°C to 870°C, 750°C to 850°C, or 770°C to 830°C. For example, the second heat treatment may be performed for 1 hour to 18 hours, 2 hours to 15 hours, 3 hours to 10 hours, or 5 hours to 9 hours. For example, the second heat treatment temperature may be lower than the first heat treatment temperature, and the second heat treatment time may be the same as or shorter than the first heat treatment time. By performing the second heat treatment under these conditions, a coating layer containing the desired aluminum, yttrium, and tungsten as active ingredients can be effectively obtained.

[0098] positive electrode In one embodiment, the positive electrode active material layer may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive agent.

[0099] The positive electrode active material may be a compound capable of reversibly inserting and extracting lithium (lithiated insertion compound), specifically, the positive electrode active materials described above. In addition, the positive electrode active material layer may further include other positive electrode active materials in addition to the positive electrode active materials described above.

[0100] According to one embodiment, the loading level of the positive electrode is 10 mg / cm 2 ~40mg / cm 2 may be, for example, 10 mg / cm 2 ~30mg / cm 2 or 10 mg / cm 2 ~20mg / cm 2Furthermore, the density of the final rolled cathode may be 3.3 g / cc to 3.7 g / cc, for example, 3.3 g / cc to 3.6 g / cc or 3.4 g / cc to 3.58 g / cc. When using a cathode active material according to an embodiment, it is advantageous to achieve such a loading level and cathode density, and a cathode satisfying the loading level and cathode density ranges is suitable for realizing a high-capacity, high-energy-density lithium secondary battery.

[0101] The binder serves to effectively adhere the positive electrode active material particles to each other and to effectively adhere the positive electrode active material to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0102] The conductive agent is used to impart conductivity to the electrode and can be any electron-conductive material that does not undergo chemical changes in the battery. Examples of the conductive agent include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0103] The current collector may be made of Al, but is not limited to this.

[0104] For example, the positive electrode may further include an additive that can serve as a sacrificial positive electrode.

[0105] The content of the positive electrode active material may be 90% by weight to 99.5% by weight relative to 100% by weight of the positive electrode active material layer, and the contents of the binder and conductive agent may be 0.5% by weight to 5% by weight each relative to 100% by weight of the positive electrode active material layer.

[0106] Lithium secondary battery In one embodiment, a lithium secondary battery is provided that includes the above-described positive electrode, negative electrode, and electrolyte.

[0107] A lithium secondary battery may include a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte.

[0108] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 1 to 4 are schematic diagrams illustrating a lithium secondary battery according to an embodiment, with FIG. 1 illustrating a cylindrical battery, FIG. 2 illustrating a prismatic battery, and FIGS. 3 and 4 illustrating pouch battery types. Referring to FIGS. 1 to 4, a lithium secondary battery 100 may include an electrode assembly 40 having a positive electrode 10 and a negative electrode 20 with a separator 30 interposed therebetween, and a case 50 housing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in FIG. 1. Also, as shown in FIG. 2, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the electrode assembly 40 to the outside.

[0109] A lithium secondary battery according to an embodiment may be suitable for being charged at a high voltage or for being driven at a high voltage. For example, the charging voltage of the lithium secondary battery may be 4.45 V or higher, such as 4.45 V to 4.7 V, 4.45 V to 4.6 V, or 4.45 V to 4.55 V. By using a positive electrode active material according to an embodiment, the lithium secondary battery may significantly reduce the amount of gas generated even when charged at a high voltage, thereby achieving high capacity and long life characteristics.

[0110] negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive agent.

[0111] The negative electrode active material includes a material capable of reversibly inserting / extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0112] The material capable of reversibly inserting / extracting lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0113] As the lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0114] As the substance capable of doping and undoping with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. As the Si-based negative electrode active material, silicon, a silicon-carbon composite, SiOx (0 < x ≤ 2), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof can be used. As the Sn-based negative electrode active material, Sn, SnO2, a Sn alloy, or a combination thereof can be used.

[0115] The silicon-carbon composite can be a composite of silicon and amorphous carbon. The average particle diameter (D 50 ) of the silicon-carbon composite particles can be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite can be in a form in which silicon particles and amorphous carbon are coated on the surface of the silicon particles. For example, it can include secondary particles (cores) formed by granulating primary silicon particles, and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon is also located between the primary silicon particles, and for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed and present in an amorphous carbon matrix.

[0116] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0117] When the silicon-carbon composite contains silicon and amorphous carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, and the content of amorphous carbon may be 50% to 90% by weight. When the composite contains silicon, amorphous carbon, and crystalline carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, the content of crystalline carbon may be 10% to 70% by weight, and the content of amorphous carbon may be 20% to 40% by weight.

[0118] In addition, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, exist in the form of a silicon alloy, or exist in an oxidized form. The oxidized form of silicon may be represented by SiO x (0 < x ≤ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution.

[0119] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material is mixed with the carbon-based negative electrode active material, the mixing ratio may be 1:99 to 90:10 by weight ratio.

[0120] The binder serves to effectively adhere the negative electrode active material particles to each other and to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0121] Non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0122] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0123] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0124] The dry binder is a fiberizable polymeric material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0125] The conductive agent is used to impart conductivity to the electrode, and any electron-conductive material that does not undergo chemical change in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0126] The content of the negative electrode active material may be 95% to 99.5% by weight, and the content of the binder may be 0.5% to 5% by weight, relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive agent.

[0127] The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and may be in the form of a foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0128] electrolyte The electrolyte for a lithium secondary battery can be, for example, an electrolytic solution, which can include a non-aqueous organic solvent and a lithium salt.

[0129] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reactions of the battery can migrate.

[0130] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0131] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0132] Examples of the ester solvent that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0133] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0134] The non-aqueous organic solvents can be used alone or in combination of two or more.

[0135] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0136] The lithium salt is a substance dissolved in an organic solvent and serves as a lithium ion source in the battery to enable basic lithium secondary battery operation and promote the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers of 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0137] The concentration of the lithium salt is preferably within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has appropriate ionic conductivity and viscosity, thereby exhibiting excellent performance and allowing lithium ions to migrate effectively.

[0138] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. Such a separator may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more of these materials. Of course, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0139] The separator may include a porous substrate and a coating layer containing an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0140] The porous substrate may be a polymer membrane formed of any one polymer selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (Teflon®), or a copolymer or mixture of two or more of these polymers.

[0141] The porous substrate can have a thickness of about 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0142] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0143] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D 50 ) can be 1 nm to 2000 nm, for example, 100 nm to 1000 nm, or 100 nm to 700 nm.

[0144] The organic and inorganic materials may be mixed in one coating layer, or may be stacked together, with one coating layer containing an organic material and one coating layer containing an inorganic material. Here, the thickness of each coating layer may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0145] The lithium secondary battery according to an embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0146] Examples of the present invention and comparative examples are described below. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0147] Example 1 1. Production of positive electrode active material Ni 0.75 Mn 0.24 Al 0.01 (OH)2 and LiOH were mixed in a molar ratio of 1:1, and the mixture was subjected to a first heat treatment at 850°C for 8 hours in an oxygen atmosphere to obtain a composition of LiNi 0.75 Mn 0.24 Al 0.01 O2 and the average particle size (D 50 A first composite oxide in the form of secondary particles having a particle size of about 14 μm was prepared.

[0148] Aluminum sulfate and yttrium nitrate were mixed with distilled water as a solvent to prepare a solution containing aluminum and yttrium raw materials. The first composite oxide was then added to the solution and stirred for approximately one hour. The aluminum content in the aluminum sulfate was designed to be 1.0 mol% based on 100 mol% of the total metals excluding lithium in the final positive electrode active material, and the yttrium content in the yttrium nitrate was designed to be 0.2 mol% based on 100 mol% of the total metals excluding lithium in the final positive electrode active material. The solvent was removed from the mixed solution, and it was dried at 190°C.

[0149] Next, the dried product was dry-mixed with tungsten oxide (WO3), a tungsten raw material, without a solvent, and then subjected to a second heat treatment at 825°C for 8 hours to obtain a cathode active material. At this time, the tungsten content in the tungsten oxide was designed and mixed to be 0.05 mol% based on 100 mol% of the total metals excluding lithium in the final cathode active material.

[0150] 2. Lithium secondary battery manufacturing 96 wt% of the prepared positive electrode active material, 2.0 wt% of polyvinylidene fluoride binder, and 2.0 wt% of carbon nanotube conductive agent were mixed to prepare a positive electrode slurry, which was then coated on an aluminum foil current collector, dried, and rolled to prepare a positive electrode. At this time, the loading level of the positive electrode was 10 mg / cm. 2 and the density of the final rolled cathode is about 3.5 g / cc.

[0151] Anode slurry was prepared by mixing 97.5 wt% graphite anode active material, 1.5 wt% carboxymethyl cellulose, and 1 wt% styrene butadiene rubber in an aqueous solvent. The anode slurry was coated onto a copper foil current collector, which was then dried and rolled to prepare an anode.

[0152] A lithium secondary battery was fabricated in a conventional manner using a polytetrafluoroethylene separator and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent containing a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7.

[0153] Example 2 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the tungsten content in the tungsten oxide was designed and mixed to be 0.1 mol % relative to 100 mol % of the total metals excluding lithium in the final cathode active material.

[0154] Example 3 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the tungsten content in the tungsten oxide was designed and mixed to be 0.2 mol % relative to 100 mol % of the total metals excluding lithium in the final cathode active material.

[0155] Example 4 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the aluminum content in aluminum sulfate was 2.0 mol % based on 100 mol % of all metals excluding lithium in the final cathode active material, the yttrium content in yttrium nitrate was 1.0 mol % based on 100 mol % of all metals excluding lithium in the final cathode active material, and the tungsten content in tungsten oxide was 1.0 mol % based on 100 mol % of all metals excluding lithium in the final cathode active material.

[0156] Comparative Example 1 When manufacturing the positive electrode active material, the aluminum and yttrium coating process and the tungsten coating process are not performed, and LiNi 0.75 Mn 0.24 Al 0.01A positive electrode active material and a lithium secondary battery were produced in substantially the same manner as in Example 1, except that the O2 composite oxide itself was used as the positive electrode active material.

[0157] Comparative Example 2 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the tungsten coating process was not performed during the preparation of the cathode active material, and only aluminum sulfate and the first composite oxide were added to a distilled water solvent without adding yttrium nitrate, followed by a second heat treatment at 825°C for 8 hours to perform only aluminum coating.

[0158] Comparative Example 3 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the tungsten coating process was not performed during the preparation of the cathode active material, and only yttrium coating was performed by adding yttrium nitrate and the first composite oxide without adding aluminum sulfate to a distilled water solvent and then performing a second heat treatment at 825°C for 8 hours.

[0159] Comparative Example 4 A cathode active material and a lithium secondary battery were prepared in substantially the same manner as in Example 1, except that, when preparing a cathode active material, yttrium coating was performed by adding only yttrium nitrate and the first composite oxide to a distilled water solvent without adding aluminum sulfate, and the yttrium content in the yttrium nitrate was designed to be 0.5 mol % relative to 100 mol % of the total metals excluding lithium in the final cathode active material, and no tungsten coating process was performed.

[0160] Comparative Example 5 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a tungsten coating process was not performed during the preparation of the cathode active material, and the content of yttrium in yttrium nitrate was designed and mixed so that it was 0.1 mol% relative to 100 mol% of the total metals excluding lithium in the final cathode active material, and then a second heat treatment was performed at 825°C for 8 hours.

[0161] Comparative Example 6 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the tungsten coating process was not performed during the preparation of the cathode active material, and a solution of aluminum sulfate and yttrium nitrate mixed in a distilled water solvent was dried and then subjected to a second heat treatment at 825°C for 8 hours.

[0162] Comparative Example 7 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a tungsten coating process was not performed during the preparation of the cathode active material, and the content of yttrium in yttrium nitrate was designed and mixed so that it was 0.5 mol % relative to 100 mol % of the total metals excluding lithium in the final cathode active material, and then a second heat treatment was performed at 825°C for 8 hours.

[0163] To facilitate understanding, the coating designs of the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 to 7 are simply shown in Table 1 below.

[0164] [Table 1]

[0165] Evaluation example 1: SEM analysis The cathode active materials prepared in Examples 2, 3, and 4 and Comparative Examples 1, 2, and 6 were photographed using a scanning electron microscope (SEM) for comparison. FIGS. 5 and 6 are SEM images of the particle surfaces of the cathode active material prepared in Comparative Example 1, which was not coated. FIGS. 7 and 8 are SEM images of the particle surfaces of the cathode active material prepared in Comparative Example 2, which was only coated with aluminum. FIGS. 9 and 10 are SEM images of the particle surfaces of the cathode active material prepared in Comparative Example 6, which was only coated with aluminum and yttrium. FIGS. 11 and 12 are SEM images of the particle surfaces of the cathode active material prepared in Example 2, and FIGS. 13 and 14 are SEM images of the particle surfaces of the cathode active material prepared in Example 3. FIG. 15 is an image of the cathode active material prepared in Example 4 photographed in BSE mode using an SEM.

[0166] Referring to FIGS. 5 to 14, it can be seen that the cathode active materials of Examples 2 and 3 have different surface morphologies from those of Comparative Examples 1, 2, and 56. Referring to FIG. 15, in the images captured using the SEM in BSE mode, the higher the atomic number, the brighter the observed surface. Therefore, the brightness varies in the order W>Y>Mn>Ni>Al. Therefore, it can be seen that the cathode active material prepared in Example 4 contains a diverse mixture of cathode active materials with different surface coatings. Furthermore, by performing SEM-EDS analysis on magnified particles of the cathode active materials with different surface coatings, as described below, it can be seen that the cathode active materials can be broadly classified into two types of cathode active materials. SEM-EDS analysis was performed using a Philips FEI Titan 80-300 at an accelerating voltage of 15 kV. The two types of cathode active materials mentioned above can be broadly identified as including a cathode active material in which a yttrium coating is prominent in the coating layer of the cathode active material (cathode active material 1) and a cathode active material in which a tungsten coating is prominent in the coating layer of the cathode active material (cathode active material 2).

[0167] Evaluation example 2: Surface analysis of positive electrode active material For surface analysis of the positive electrode active materials, positive electrode active material 1 and positive electrode active material 2 described in Evaluation Example 1 were selected and subjected to SEM-EDS analysis of their surfaces, and the results are shown in Figures 16 and 18, respectively. Here, SEM-EDS was performed using a Philips FEI Titan 80-300 at an accelerating voltage of 15 kV.

[0168] 16 and 18, it can be seen that the cathode active materials 1 and 2 prepared in Example 4 have a coating layer containing Al, Y, and W formed on the surface thereof.

[0169] Furthermore, by comparing the results of elemental analysis of aluminum (Al), yttrium (Y), tungsten (W), and oxygen (O) at the same point on the surface of the positive electrode active material, it was found that aluminum, yttrium, and tungsten exist in the form of oxides in the coating layer.

[0170] Evaluation example 3: Cross-sectional analysis of positive electrode active material For surface analysis of the positive electrode active materials, positive electrode active material 1 and positive electrode active material 2 described in Evaluation Example 1 were selected and subjected to SEM-EDS analysis of their cross sections, and the results are shown in Figures 17 and 19, respectively. Here, SEM-EDS was performed using a Philips FEI Titan 80-300 at an accelerating voltage of 15 kV.

[0171] 17 and 19, it can be seen that the coating layer of the cathode active material prepared in Example 4 is formed in the range of 30 nm to 1 μm, and it can also be seen that aluminum exists in the form of a continuous film or islands in the coating layer of the cathode active material.

[0172] Meanwhile, it can be seen that yttrium exists in an island shape in the coating layer of cathode active material 1 as shown in Figure 17, and tungsten exists in an island shape in the coating layer of cathode active material 2 as shown in Figure 19. Therefore, it can be confirmed that at least one selected from yttrium and tungsten exists in an island shape in the coating layer of the cathode active material prepared in Example 4. It can also be confirmed that the cathode active material prepared in Example 4 has the above-mentioned island shape formed in the coating layer with a thickness ranging from 10 nm to 500 nm.

[0173] Evaluation example 4: Analysis of grain boundaries and internal pores of core particles The aluminum (Al) component analysis results in Figure 17 confirm that aluminum is present in the grain boundary coating located on the surface of the primary particles inside the secondary particles of the core particles of the positive electrode active material. Also, the tungsten (W) component analysis results in Figure 19 confirm that tungsten is also present in the internal pores of the core particles of the positive electrode active material.

[0174] Evaluation example 5: Evaluation of initial charge / discharge capacity and efficiency The lithium secondary batteries manufactured in Examples 1 to 3 and Comparative Examples 1 to 7 were initially charged and discharged at 25° C. at a constant current of 0.2 C to an upper limit voltage of 4.45 V, at a constant voltage of 0.05 C, and then discharged at 0.2 C to an end voltage of 3.0 V. Table 2 below shows the initial charge capacity and initial discharge capacity, as well as the ratio of the latter to the former calculated as efficiency.

[0175] Evaluation example 6: High temperature life characteristics Following the initial charge and discharge of Evaluation Example 5, a cycle of charging at 1.0 C and discharging at 1.0 C in a voltage range of 3.0 V to 4.45 V at 45°C was repeated 50 times or more, and the ratio of the 50-cycle discharge capacity to the initial discharge capacity was calculated and shown in Table 2 below.

[0176] Evaluation example 7: Evaluation of gas generation rate The batteries of Examples 1 to 4 and Comparative Examples 1 to 7 were initially charged at 4.45 V as in Evaluation Example 5, and then stored at 90°C for 4 hours, after which the amount of gas generated in the batteries was measured. The results are shown in Table 2 below.

[0177] [Table 2]

[0178] Referring to Table 2, it can be seen that the lithium secondary batteries of Examples 1 to 4 have charge / discharge capacity and efficiency characteristics at the same level as the comparative example, while also excelling in one or more of the effects of improved high-temperature life characteristics and reduced gas generation under high-voltage and high-temperature conditions.

[0179] In particular, Comparative Example 1, which was not coated, had poor high-temperature life characteristics and the highest gas generation rate. Comparative Example 2, which was coated only with aluminum, and Comparative Examples 3 and 4, which were coated only with yttrium, showed higher gas generation rates under high voltage and high temperature conditions than the Examples.

[0180] Furthermore, in the case of Comparative Examples 5 to 7, which were coated with aluminum and yttrium but not with tungsten, the high temperature life characteristics were somewhat lower or the amount of gas generation was higher.

[0181] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also fall within the scope of the present invention. [Explanation of symbols]

[0182] 100: Lithium secondary battery 10: Positive electrode 11: Positive electrode lead tab 12: Positive terminal 20: Negative electrode 21: Negative electrode lead tab 22: Negative terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing material 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. Core particles containing a lithium nickel-based composite oxide; and a coating layer located on the surface of the core particle and containing aluminum, yttrium, and tungsten.

2. 2. The positive electrode active material according to claim 1, wherein the core particles are a lithium nickel-manganese-aluminum composite oxide.

3. 2. The positive electrode active material according to claim 1, wherein the content of nickel is 60 mol % to 80 mol % relative to 100 mol % of all metals excluding lithium.

4. 2. The cathode active material of claim 1, wherein the coating layer has an aluminum content of 0.1 mol% to 2.5 mol%, an yttrium content of 0.05 mol% to 1.5 mol%, and a tungsten content of 0.01 mol% to 1.5 mol%, based on 100 mol% of all metals excluding lithium.

5. The yttrium content of the coating layer (C Y tungsten content (C W ) molar ratio (C W / C Y 2. The positive electrode active material according to claim 1, wherein σ is 0.01 to 1.

0.

6. The aluminum content of the coating layer (C Al tungsten content (C W ) molar ratio (C W / C Al 2. The positive electrode active material according to claim 1, wherein σ is 0.01 to 0.

5.

7. The cathode active material of claim 1, wherein the coating layer has a thickness of 30 nm to 1 μm.

8. The positive electrode active material according to claim 1 , wherein aluminum, yttrium, and tungsten are present in the coating layer.

9. 2. The positive electrode active material of claim 1, wherein the aluminum, yttrium, and tungsten in the coating layer are present in the form of oxides.

10. 2. The cathode active material of claim 1, wherein the coating layer comprises aluminum oxide, yttrium oxide, and tungsten oxide.

11. The positive electrode active material of claim 1 , wherein the aluminum in the coating layer is present in the form of a continuous film or in the form of islands.

12. The positive electrode active material of claim 1 , wherein at least one selected from aluminum, yttrium, and tungsten is present in the coating layer in the form of islands.

13. The positive electrode active material of claim 1 , wherein the coating layer contains at least one selected from the group consisting of yttrium and tungsten, and the at least one selected from the group consisting of yttrium and tungsten, in the form of islands.

14. The positive electrode active material according to claim 12, wherein the island shape has a thickness of 10 nm to 500 nm.

15. The positive electrode active material of claim 1 , further comprising tungsten in the internal pores of the core particle.

16. The core particle is in the form of a secondary particle formed by aggregating a plurality of primary particles, The positive electrode active material of claim 1 , further comprising a grain boundary coating portion located on a surface of the primary particle inside the secondary particle and containing aluminum.

17. mixing a nickel-based composite hydroxide and a lithium raw material and subjecting the mixture to a first heat treatment to obtain a first composite oxide; The first composite oxide is added to a solution in which an aluminum raw material and an yttrium raw material are mixed in an aqueous solvent, and the mixture is then dried. the dried product is dry-mixed with a tungsten raw material, and the mixture is subjected to a second heat treatment to obtain a cathode active material.

18. The first heat treatment is carried out at 750°C to 950°C, The drying is carried out at 40°C to 300°C, The method for producing a positive electrode active material according to claim 17, wherein the second heat treatment is performed at 700°C to 900°C.

19. current collector, and a positive electrode active material layer located on the current collector, The positive electrode active material layer comprises the positive electrode active material according to any one of claims 1 to 16.

20. The positive electrode according to claim 19 . a negative electrode, and A lithium secondary battery containing an electrolyte.

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