Positive electrode active material, method for manufacturing the same, positive electrode containing the same, and lithium secondary battery

Abstract

To provide a positive electrode active material including a lithium nickel-manganese complex oxide, in which economical efficiency, high capacity, and long-life characteristics are secured, and a high-voltage characteristic and a high-temperature characteristic are improved, a manufacturing method for the same, a positive electrode including the same, and a lithium secondary battery.SOLUTION: A positive electrode active material includes a core particle containing a lithium nickel-manganese complex oxide in which the content of nickel is 60 mol% or more relative to 100 mol% of the entire metals excluding lithium, and a coating layer existing on a surface of the core particle and containing Al, Zr, and Mg. A manufacturing method for the positive electrode active material, and a positive electrode and a lithium secondary battery including the positive electrode active material are also provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This 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] Lithium-ion batteries, which offer high energy density while remaining portable, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, research has been actively conducted on using high-energy-density lithium-ion batteries as power sources or energy storage sources for hybrid and electric vehicles.

[0003] To realize lithium secondary batteries that meet these applications, a variety of positive electrode active materials are being considered. Among them, lithium nickel oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt oxides are mainly used as positive electrode active materials. However, in recent years, while the demand for large, high-capacity, or high-energy-density lithium secondary batteries has surged, the supply of positive electrode active materials containing cobalt, a rare metal, is expected to be extremely insufficient. In other words, because cobalt is expensive and its remaining reserves are not large, there is a need to develop positive electrode active materials that either exclude cobalt or reduce its content. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention provides a positive electrode active material comprising a lithium nickel-manganese composite oxide, which ensures economic efficiency, high capacity, and long lifespan, and improves high-voltage and high-temperature characteristics, as well as a method for producing the same, and a positive electrode and lithium secondary battery containing the same. [Means for solving the problem]

[0005] In one embodiment of the present invention, there is provided a core particle containing a lithium nickel-manganese composite oxide in which the nickel content is 60 mol% or more with respect to 100 mol% of the total metal excluding lithium, and a cathode active material including a coating layer containing Al, Zr, and Mg and located on the surface of the core particle.

[0006] In another embodiment of the present invention, there is provided a method for manufacturing a cathode active material, including: (i) mixing a nickel-manganese composite hydroxide in which the nickel content is 60 mol% or more with respect to 100 mol% of the total metal and a lithium raw material, and subjecting the mixture to a first heat treatment to obtain a lithium nickel-manganese composite oxide; (ii) introducing and mixing the obtained lithium nickel-manganese composite oxide into a solution in which an Al raw material is mixed in an aqueous solvent, followed by drying; and (iii) dry-mixing the obtained product with a Zr raw material and a Mg raw material and subjecting the mixture to a second heat treatment to obtain a cathode active material.

[0007] In another embodiment of the present invention, there is provided a cathode including a cathode current collector and a cathode active material layer located on the cathode current collector, wherein the cathode active material layer includes the above-described cathode active material.

[0008] In another embodiment of the present invention, there is provided a lithium secondary battery including the above-described cathode, anode, and electrolyte.

Advantages of the Invention

[0009] The cathode active material according to one embodiment of the present invention minimizes production cost and maximizes capacity, ensures long-life characteristics, and improves characteristics at high voltage and high-temperature characteristics. The lithium secondary battery applying the above-described cathode active material can exhibit high initial charge-discharge capacity and efficiency even under high-voltage conditions, can realize long-life characteristics, and can effectively suppress gas generation problems due to high-voltage and high-temperature driving.

Brief Description of the Drawings

[0010] [Figure 1] It is a cross-sectional view schematically showing a lithium secondary battery according to one embodiment. [Modes for carrying out the invention]

[0011] The following describes specific embodiments in detail so that they can be easily implemented by those with ordinary skill in the art. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0012] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Unless otherwise clearly stated in the context, singular expressions include plural expressions.

[0013] Here, "these combinations" refers to mixtures of components, laminates, composites, copolymers, alloys, blends, reaction products, etc.

[0014] Here, terms such as “include,” “equip,” or “possess” are intended to specify the existence of a particular feature, number, stage, component, or combination thereof, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, numbers, stages, components, or combinations thereof.

[0015] To clearly represent various layers and regions in the drawings, thicknesses are shown enlarged, and similar parts are given the same drawing reference numerals throughout the specification. When a layer, film, region, plate, or other part is said to be "on top of" or "on" another part, this includes not only when it is "directly on top of" another part, but also when there is another part in between. Conversely, when a part is said to be "directly on top of" another part, it means that there is no other part in between.

[0016] Furthermore, the term "layer" here includes not only the shapes formed on the entire surface when observed in a plan view, but also the shapes formed on a portion of the surface.

[0017] The average particle size can be measured by methods widely known to those skilled in the art, for example, by a particle size analyzer, or by a transmission electron microscope image or scanning electron microscope image. Alternatively, it can be measured using dynamic light scattering, and after performing data analysis to count the number of particles for each particle size range, the average particle size value can be calculated from this. Unless otherwise defined, the average particle size means the diameter (D50) of the particle whose cumulative volume in the particle size distribution is 50% by volume. Or, unless otherwise defined, the average particle size may be obtained by measuring the size (diameter or length of the major axis) of more than 20 random particles from a scanning electron microscope image to obtain a particle size distribution, and then taking the diameter (D50) of the particle whose cumulative volume in the said particle size distribution is 50% by volume as the average particle size.

[0018] Here, "or" is not interpreted in an exclusive sense; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0019] The term "metal" is interpreted as a concept that includes general metals, transition metals, and metalloids (metallic semi-metals).

[0020] positive electrode active material One embodiment of the present invention provides a positive electrode active material comprising core particles containing a lithium nickel-manganese composite oxide in which the nickel content is 60 mol% or more relative to 100 mol% of the total metal excluding lithium, and a coating layer located on the surface of the core particles and containing Al, Zr, and Mg.

[0021] In recent years, with the sharp rise in the price of cobalt, a rare metal, there has been a demand for the development of cathode active materials that either exclude cobalt or reduce its cobalt content. Among these, cathode active materials with olivine-based crystal structures such as lithium iron phosphate (LFP), lithium manganese phosphate (LMP), and lithium iron manganese phosphate (LMFP), or spinel crystal structures such as lithium manganese oxide (LMO), have limitations in achieving high capacity because the amount of lithium that can be utilized within the structure is small. Layered nickel-manganese cathode active materials can have a high lithium content within the structure, resulting in excellent capacity and efficiency characteristics, making them suitable as materials for high-capacity batteries. However, the removal of cobalt, which plays a core role in the layered structure, leads to a decrease in structural stability, an increase in resistance, and difficulty in ensuring long life characteristics. Furthermore, because cobalt is removed, side reactions between the cathode active material and electrolyte accelerate under high voltage and high temperature conditions, increasing gas generation and reducing life characteristics.

[0022] In one embodiment, a cathode active material is provided that maximizes capacity and efficiency while minimizing production costs, reduces gas generation even under high voltage and high temperature conditions, and achieves long-life characteristics by introducing a coating layer containing Al, Zr, and Mg while applying a layered lithium nickel-manganese composite oxide to the core particles.

[0023] core particle The core particles contain a lithium nickel-manganese composite oxide, and the nickel content satisfies the requirement of 60 mol% or more relative to 100 mol% of the total metal excluding lithium in the positive electrode active material. Although nickel is contained in the core particles, some may migrate to the coating layer during the coating process; therefore, the nickel content refers to the total nickel content in the positive electrode active material. The nickel content 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%, relative to 100 mol% of the total metal excluding lithium in the positive electrode active material. When the nickel content satisfies the above range, high capacity can be achieved, and structural safety can be enhanced even if the cobalt content is reduced.

[0024] The manganese content is, for example, 10 mol% to 40 mol% relative to 100 mol% of the total metal excluding lithium in the lithium nickel-manganese composite oxide, and can 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%, 20 mol% to 30%, etc. When the manganese content satisfies the above range, the positive electrode active material can achieve high capacity while improving structural stability.

[0025] A lithium nickel-manganese composite oxide may, as an example, be a lithium nickel-manganese-aluminum composite oxide that further contains aluminum in addition to nickel and manganese. When aluminum is included in the composite oxide, it is advantageous for maintaining a stable layered structure even if the cobalt element is removed from the structure. The aluminum content per 100 mol% of the lithium nickel-manganese-aluminum composite oxide is 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%. When the aluminum content satisfies the above range, a stable layered structure can be maintained even if cobalt is removed, the problem of structural collapse due to charging and discharging can be suppressed, and the long-life characteristics of the positive electrode active material can be achieved.

[0026] According to one embodiment, the concentration of aluminum in the core particles can be uniform. That is, it means that aluminum does not have a concentration gradient from the center to the surface direction within the core particles, or the aluminum concentration inside the core particles is not higher or lower than that outside, and the aluminum in the core particles is uniformly dispersed. This can be said to be a structure obtained by synthesizing a composite oxide using a nickel-manganese-aluminum hydroxide as a precursor by using an aluminum raw material during the production of the precursor without further doping aluminum during the synthesis process of the core particles. The core particles can be in the form of secondary particles in which a plurality of primary particles are aggregated, but it can be said that the aluminum content inside the primary particles is the same or similar regardless of the position of the primary particles. That is, when a primary particle is selected from an arbitrary position in the cross-section of the secondary particle and the aluminum content inside rather than at the interface of the primary particle is measured, it can be expressed that the aluminum content is the same / similar / uniform regardless of the position of the primary particle, that is, whether the primary particle is close to the center or the surface of the secondary particle. In such a structure, even if cobalt is not present or is present in an extremely small amount, a stable layered structure can be maintained, no aluminum by-products or aluminum aggregates are generated, and the capacity, efficiency, and life characteristics of the positive electrode active material can be improved simultaneously.

[0027] The lithium nickel-manganese composite oxide is specifically represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1

[0028] In Chemical Formula 1, 0.9 ≦ a1 ≦ 1.8, 0.6 ≦ x1 ≦ 0.8, 0.1 ≦ y1 ≦ 0.4, 0 ≦ z1 ≦ 0.03, 0 ≦ w1 ≦ 0.3, 0.9 ≦ x1 + y1 + z1 + w1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zr, and X is one or more elements selected from F, P, and S.

[0029] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.5, or 0.9 ≤ a1 ≤ 1.2 may hold. Also, Chemical Formula 1 contains aluminum, and in this case, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 ≤ z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 can be satisfied. For example, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 < z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 can be satisfied.

[0030] In Chemical Formula 1, for example, 0.6 ≤ x1 ≤ 0.79, 0.6 ≤ x1 ≤ 0.78, 0.6 ≤ x1 ≤ 0.75, 0.65 ≤ x1 ≤ 0.8, or 0.7 ≤ x1 ≤ 0.79; 0.1 ≤ y1 ≤ 0.35, 0.1 ≤ y1 ≤ 0.30, 0.1 ≤ y1 ≤ 0.29, 0.15 ≤ y1 ≤ 0.39, or 0.2 ≤ y1 ≤ 0.3; 0.01 ≤ z1 ≤ 0.025, 0.01 < z1 ≤ 0.02, or 0.01 < z1 ≤ 0.019; and 0 ≤ w1 ≤ 0.28, 0 ≤ w1 ≤ 0.27, 0 ≤ w1 ≤ 0.26, 0 ≤ w1 ≤ 0.25, 0 ≤ w1 ≤ 0.24, 0 ≤ w1 ≤ 0.23, 0 ≤ w1 ≤ 0.22, 0 ≤ w1 ≤ 0.21, 0 ≤ w1 ≤ 0.2, 0 ≤ w1 ≤ 0.15, 0 ≤ w1 ≤ 0.1, or 0 ≤ w1 ≤ 0.09, etc. may hold.

[0031] The lithium nickel-manganese composite oxide may be a cobalt-free compound that does not contain cobalt or contains a very small amount of cobalt. For example, the content of cobalt in the lithium nickel-manganese composite oxide may be 0 mol% to 0.01 mol% based on 100 mol% of the total metal excluding lithium.

[0032] The core particle may be in the form of a secondary particle formed by the aggregation of multiple primary particles. The secondary particle may be spherical, ellipsoidal, polyhedronal, or irregular in shape, and the primary particle may be spherical, ellipsoidal, plate-like, or a combination thereof.

[0033] The aforementioned core particles are susceptible to chemical attack from components within the electrolyte when the battery is operated under high voltage or high temperature conditions, potentially leading to numerous side reactions with the electrolyte. This can result in increased gas generation, reducing battery life and safety. However, these problems can be resolved by introducing a coating layer according to one embodiment described later.

[0034] coating layer One embodiment is characterized in that Al, Zr, and Mg are all included in the coating layer, and compared to the case where any one of the three is excluded, the amount of gas generated under high voltage or high temperature operating conditions can be significantly reduced, and the lifespan characteristics are improved. 3+ , Zr 4+ , and Mg 2+ It can be said that it contains three types of metals or metal cations. The simultaneous coating of three types of metal cations with oxidation states of 2+, 3+, and 4+ increases the charge balance, which can improve high-voltage characteristics.

[0035] The Al content in the coating layer is 0.1 mol% to 2 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material, and can be, for example, 0.2 mol% to 1.9 mol%, 0.3 mol% to 1.8 mol%, 0.5 mol% to 1.5 mol%, or 0.8 mol% to 1.3 mol%. This refers only to the aluminum content in the coating layer, separate from the aluminum contained in the core particles. The aluminum content in 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 in the coating layer meets the above range, it is possible to form a uniform and thin coating layer, the resistance of the positive electrode active material does not increase, side reactions with the electrolyte are effectively suppressed, and the life characteristics of the lithium secondary battery under high voltage and high temperature conditions can be improved. For example, if the aluminum content of the coating layer is too high, a uniform coating layer may not be formed, or the resistance may increase, reducing the charge-discharge efficiency and lifespan characteristics. Conversely, if the aluminum content of the coating layer is too low, a coating layer of the appropriate thickness may not be formed, reducing the effect of suppressing side reactions with the electrolyte.

[0036] The Zr content of the coating layer is 0.1 mol% to 0.4 mol%, for example, 0.2 mol% to 0.4 mol%. The Mg content of the coating layer is 0.1 mol% to 0.5 mol%, for example, 0.1 mol% to 0.4 mol%. When the coating content of Zr and Mg satisfies the above ranges, a good coating layer is formed in the positive electrode active material 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.

[0037] In the aforementioned coating layer, the ratio of Zr and Mg content to Al content is 0.06 to 0.65, for example, 0.1 to 0.6, 0.1 to 0.5, 0.1 to 0.45, or 0.2 to 0.40, and can be greater than 0.06 and less than 0.65, or greater than 0.06 and less than 0.45. This represents the content ratio of (Zr + Mg) / Al, where content refers to molar content. When the content ratio of each element in the coating layer satisfies the above range, the capacitance characteristics and lifetime characteristics at high voltage can be maximized.

[0038] In one embodiment, the coating layer is in the form of a film that continuously surrounds the surface of the core particles, and may, for example, be in the form of a shell that surrounds the entire surface of the core particles. This is distinct from a structure in which only a part of the surface of the core particles is partially coated. According to one embodiment, the coating layer can be formed to surround the entire surface of the core particles while being very thin and having a uniform thickness. As a result, the positive electrode active material does not experience an increase in resistance or a decrease in capacity, its structural stability is improved, side reactions with the electrolyte are effectively suppressed, gas generation under high voltage and high temperature conditions is reduced, and long-life characteristics can be achieved.

[0039] The thickness of the coating layer is 5 nm to 500 nm, and may be, for example, 5 nm to 450 nm, 10 nm to 400 nm, 20 nm to 350 nm, 30 nm to 300 nm, 30 nm to 250 nm, 30 nm to 200 nm, 30 nm to 150 nm, 50 nm to 500 nm, 80 nm to 500 nm, or 100 nm to 500 nm. When the coating layer satisfies the above thickness range, the structural stability of the positive electrode active material can be improved and side reactions with the electrolyte can be effectively suppressed without increasing resistance or decreasing capacitance due to the coating. The thickness of the coating layer can be measured by, for example, TOF-SIMS, XPS, or EDS analysis, and the thickness range of the coating layer may be measured by TEM-EDS line profile.

[0040] One embodiment is characterized by having a thin coating layer at the level of tens to hundreds of nanometers, and having a uniform thickness. For example, the thickness deviation of the coating layer within a single positive electrode active material particle may be 20% or less, 18% or less, or 15% or less. Here, the thickness deviation of the coating layer refers to the content of the thickness of the coating layer within a single positive electrode active material particle. The thickness deviation of the coating layer means, for example, that the thickness of more than 10 points is measured in an electron microscope image of the cross-section of a single positive electrode active material particle, the arithmetic mean is calculated, the absolute value of the difference between one data point and the arithmetic mean is divided by the arithmetic mean, and multiplied by 100. When the thickness deviation or standard deviation of the coating layer satisfies the above range, it means that a coating layer of uniform thickness is well formed in film form on the surface of the positive electrode active material particle, thereby improving the structural stability of the positive electrode active material, effectively suppressing side reactions with the electrolyte, and minimizing the increase in resistance and decrease in capacity due to the coating.

[0041] Due to the properties of each element in the coating layer, Al may exist as a continuous film, while Zr and Mg may exist as islands.

[0042] In one embodiment, Al, Zr, and Mg may each form separate layers. For example, the positive electrode active material according to one embodiment may include a first coating layer containing Al located on the surface of the core particles, and a second coating layer containing Zr and Mg located on the first coating layer. First, a thin film-like first coating layer is formed as aluminum adheres to or is absorbed onto the surface of the core particles, and then a second coating layer is formed on top of that as zirconium and magnesium are coated. Of course, Al, Zr, and Mg are mixed in the first and second coating layers, but the first coating layer can be said to be an Al-rich coating layer with Al as the main component, and the second coating layer can be said to be a Zr / Mg-rich coating layer with Zr and Mg as the main components.

[0043] The thicknesses of the first and second coating layers are not particularly limited, but the thickness of the first coating layer is 1 nm to 200 nm, for example, 10 nm to 200 nm, 20 nm to 200 nm, or 30 nm to 180 nm. The thickness of the second coating layer is 2 nm to 300 nm, for example, 10 nm to 250 nm, 20 nm to 200 nm, 30 nm to 300 nm, or 50 nm to 300 nm. When the thicknesses of each layer meet the above ranges, the coating improves the structural stability of the positive electrode active material without increasing resistance or decreasing capacitance, effectively suppresses side reactions with the electrolyte, and effectively reduces gas generation during high-voltage and high-temperature operation.

[0044] On the other hand, the coating layer may further contain nickel, manganese, or a combination thereof, in addition to Al, Zr, and Mg. The nickel and manganese are those that were present in the core particles and flowed in during the coating layer formation process, and their content is not particularly limited. In one embodiment, the coating layer must contain Al, Zr, and Mg while selectively containing nickel and manganese, allowing it to be formed to a thin and uniform thickness, improving the high-voltage characteristics of the positive electrode active material and enhancing its lifespan.

[0045] grain boundary coating section During the coating layer formation process, aluminum can diffuse into the core particles. This allows the positive electrode active material in one embodiment to further include a grain boundary coating region containing aluminum, located on the surface of primary particles within secondary particles. Here, secondary particles refer to core particles, and the interior of secondary particles refers to the entire interior excluding the surface of the secondary particle, or it can refer to the region from the surface of the secondary particle to approximately 60% of the radius in the direction towards the center of the secondary particle. The grain boundary coating region is a concept distinct from the coating layer on the core particle surface, and refers to a coating region formed on the surface of primary particles located within the core particles. The presence of the grain boundary coating region can be confirmed by SEM-EDS analysis of the cross-section of the positive electrode active material. The formation of the aluminum grain boundary coating region further stabilizes the positive electrode active material structurally, improving its lifetime characteristics.

[0046] The aluminum content within the grain boundary coating is not particularly limited; for example, the aluminum content within the grain boundary coating may be less than the aluminum content within the coating layer.

[0047] The grain boundary coating may further contain magnesium in addition to aluminum. Furthermore, the grain boundary coating may further contain nickel, manganese, or a combination thereof.

[0048] Average particle size of positive electrode active material (D) according to one embodiment 50 The average particle size is not particularly limited, but 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 obtained by measuring the size (diameter or length of the long axis) of more than 20 random particles in a scanning electron microscope image of the positive electrode active material to obtain a particle size distribution, and the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50 volume% is the average particle size. 50 This may be taken as the average particle size. When the average particle size of the positive electrode active material satisfies the above range, high capacity and long life can be achieved, and it is advantageous to form a coating layer according to one embodiment.

[0049] In one embodiment, the cobalt content of the positive electrode active material is, for example, 0.01 mol% or less, 0.005 mol% or less, or 0.001 mol% or less relative to 100 mol% of the total metal excluding lithium, and may be, for example, 0 mol% to 0.01 mol%. The positive electrode active material in one embodiment may be, for example, a cobalt-free positive electrode active material.

[0050] Furthermore, the positive electrode active material according to one embodiment may be characterized by not containing sodium. Generally, sodium ions can be used in the manufacturing process of positive electrode active materials, but according to the manufacturing method described later, core particles with a stable structure and a coating layer of uniform thickness can be formed without using sodium ions.

[0051] Method for manufacturing positive electrode active material In one embodiment, a method for producing a positive electrode active material is provided, which includes (i) mixing a nickel-manganese composite hydroxide having a nickel content of 60 mol% or more relative to 100 mol% of the total metal with a lithium raw material, and performing a first heat treatment to obtain a lithium nickel-manganese composite oxide, (ii) adding the obtained lithium nickel-manganese composite oxide to a solution in which an Al raw material is mixed with an aqueous solvent and mixing, then drying, and (iii) dry mixing the obtained material with a Zr raw material and a Mg raw material and performing a second heat treatment to obtain a positive electrode active material.

[0052] Nickel-manganese composite hydroxides may contain no cobalt or only a very small amount of cobalt, for example, cobalt-free nickel-manganese composite hydroxides, and as an example, cobalt-free nickel-manganese-aluminum composite hydroxides. Nickel-manganese composite hydroxides can be produced by a general coprecipitation method.

[0053] In nickel-manganese composite hydroxides, the nickel content is 60 mol% or more relative to 100 mol% of the total metal, and can 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%. When the nickel content meets the above range, high capacity can be achieved, and structural safety can be improved even if the cobalt content is reduced.

[0054] In nickel-manganese composite hydroxides, the manganese content is typically 10 mol% to 40 mol% relative to 100 mol% of the total metal, and can range from 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%, and so on.

[0055] Furthermore, if the nickel-manganese composite hydroxide also contains aluminum, the aluminum content is 0.1 mol% or more, 0.5 mol% or more, or 1 mol% or more relative to 100 mol% of the total metal, 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%. When the manganese and aluminum content of the composite hydroxide satisfies the above ranges, it is possible to improve the structural safety of the positive electrode active material while achieving high capacity, thereby lowering production costs and improving economic efficiency.

[0056] In nickel-manganese composite hydroxides, the cobalt content can be 0.01 mol% or less, 0.005 mol% or less, or 0.001 mol% or less relative to 100 mol% of the total metal. Such nickel-manganese composite hydroxides can avoid the increase in unit cost due to cobalt, are economical, maximize capacity, and have improved structural stability.

[0057] Nickel-manganese complex hydroxides are represented, for example, by the following chemical formula 2. [Chemical formula 2] Ni x2 Mn y2Al z2 M 2 w2 (OH)2

[0058] In chemical formula 2, 0.6 ≤ x² ≤ 0.8, 0.1 ≤ y² ≤ 0.4, 0 ≤ z² ≤ 0.03, 0 ≤ w² ≤ 0.3, and 0.9 ≤ x² + y² + z² + w² ≤ 1.1, and M 2 is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zr.

[0059] In the aforementioned chemical formula 2, for example, 0.6 ≤ x² ≤ 0.8, 0.1 ≤ y² ≤ 0.39, 0.01 ≤ z² ≤ 0.03, and 0 ≤ w² ≤ 0.29 may be present.

[0060] Nickel-manganese composite hydroxides are in particulate form, and the average particle size (D) of these particles is 50 The size of the septum can be 10 μm to 18 μm, 11 μm to 16 μm, or 12 μm to 15 μm.

[0061] By not further doping with aluminum during the core particle preparation process and by using aluminum raw materials during precursor production, a nickel-manganese-aluminum composite hydroxide in which aluminum is uniformly dispersed within the structure can be used as a precursor. Using such a precursor makes it possible to produce a positive electrode active material that maintains a stable layered structure even after repeated charge-discharge cycles, without containing cobalt. This prevents the formation of aluminum by-products and aluminum aggregates, improving the capacity, efficiency, and lifespan characteristics of the positive electrode active material.

[0062] Nickel-manganese composite hydroxide and lithium raw materials can be mixed in a molar ratio of 1:0.9 to 1:1.8, for example, in a molar ratio of 1:0.9 to 1:1.5 or 1:0.9 to 1:1.2. The first heat treatment can be carried out in an oxygen atmosphere, for example, in a temperature range of 750°C to 950°C, or 780°C to 900°C, or 810°C to 890°C, for 2 to 20 hours, or 4 to 12 hours. The heat treatment can yield lithium nickel-manganese composite oxide. The obtained composite oxide contains 60 mol% or more nickel per 100 mol% of the total metal, for example, 60 mol% to 80 mol%, and contains no cobalt or only a very small amount of 0.01 mol% or less.

[0063] Lithium nickel-manganese composite oxides differ considerably from existing nickel-based oxides of other compositions, such as lithium nickel-cobalt-manganese composite oxides and lithium nickel-cobalt-aluminum composite oxides, in terms of residual lithium content on the particle surface and many of the surface properties. Therefore, existing coating methods cannot form a good coating layer with a uniform film morphology. In one embodiment, a method is provided to improve high-voltage characteristics by forming a very thin and uniform coating layer on the surface of a lithium nickel-manganese composite oxide having a very small cobalt content and a nickel content of 60 mol% or more.

[0064] In one embodiment, the lithium nickel-manganese composite oxide obtained by the first heat treatment is added to an aqueous solvent mixed with aluminum raw materials and mixed, then dried and subjected to a second heat treatment to perform an AI coating using a type of wet method.

[0065] The aqueous solvent may include distilled water, an alcoholic solvent, or a combination thereof. The aluminum raw material may include, for example, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum hydroxide, or a combination thereof. As an example, the aluminum raw material may include aluminum sulfate, in which case it is advantageous to form a coating layer with uniform thickness on the surface of lithium nickel-manganese composite oxide particles.

[0066] The aluminum raw material is used to form the coating layer, and the aluminum content in the aluminum raw material can be designed to be 0.1 mol% to 2 mol% relative to 100 mol% of the total metal excluding lithium in the final cathode active material. For example, it can be designed to be 0.2 mol% to 1.9 mol%, 0.3 mol% to 1.8 mol%, 0.5 mol% to 1.5 mol%, or 0.8 mol% to 1.3 mol%. By designing the aluminum content of the AI ​​coating within the above ranges, it is possible to form a coating layer with a thin thickness of tens to hundreds of nanometers and a uniform thickness, thereby reducing the amount of gas generated in lithium secondary batteries under high voltage or high temperature operating conditions and improving high capacity and long life characteristics.

[0067] The solution obtained by mixing the aluminum raw material with an aqueous solvent has a pH of 1.5 to 3.5, and may be, for example, 2.0 to 3.4, 2.5 to 3.3, 2.7 to 3.3, or 2.9 to 3.2. The lithium nickel-manganese composite oxide can be added to the aqueous solvent containing the aluminum raw material and mixed for approximately 5 to 80 minutes, or 5 to 60 minutes, or 5 to 40 minutes. The mixed solution after stirring has a pH of 4.5 to 8.5, and may be, for example, 5.0 to 8.0, 5.5 to 7.5, or 6.0 to 7.0. Meeting these conditions is advantageous for forming a coating layer of uniform thickness.

[0068] The drying process after the mixing step can be understood as a step to remove the solvent, and can be carried out, for example, at 40°C to 240°C, 100°C to 220°C, or 150°C to 200°C.

[0069] The second heat treatment can be understood as a process for forming an Al / Zr / Mg coating layer, and can be carried out, for example, in an oxygen atmosphere at a temperature range of 700°C to 850°C, 750°C to 840°C, or 800°C to 830°C for 2 to 20 hours, or 3 to 10 hours. Furthermore, the temperature of the second heat treatment can be lower than that of the first heat treatment, and the duration of the second heat treatment is preferably the same as or shorter than that of the first heat treatment. By performing the second heat treatment under these conditions, the desired coating layer can be obtained.

[0070] The Zr content in the Zr raw material can be designed to be 0.1 mol% to 0.4 mol%, or 0.2 mol% to 0.4 mol%, relative to 100 mol% of the total metal excluding lithium in the positive electrode active material. Similarly, the Mg content in the Mg raw material can be designed to be 0.1 mol% to 0.5 mol%, or 0.1 mol% to 0.4 mol%, relative to 100 mol% of the total metal excluding lithium in the positive electrode active material.

[0071] The Zr raw material may include, for example, zirconium oxide, zirconium silicate, or a combination thereof. The Mg raw material may include, for example, magnesium oxide, magnesium phosphate, magnesium carbonate, or a combination thereof.

[0072] positive electrode In one embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer provides a positive electrode containing the positive electrode active material described above. The positive electrode active material layer may further contain other types of positive electrode active materials in addition to the positive electrode active material described above. The positive electrode active material layer may also selectively further contain a binder, a conductive material, or a combination thereof.

[0073] According to one embodiment, the loading level of the positive electrode active material layer is 5 mg / cm³. 2 ~40 mg / cm³ 2 For example, 5 mg / cm³ 2 ~30 mg / cm³2 or 10 mg / cm³ 2 ~20 mg / cm³ 2 Or 10±5 mg / cm³ 2 This is possible. Furthermore, the density of the positive electrode active material layer in the rolled final positive electrode is 3.3 g / cc to 3.7 g / cc, and can be, for example, 3.3 g / cc to 3.6 g / cc or 3.4 g / cc to 3.58 g / cc. When applying the positive electrode active material according to one embodiment, it is advantageous to achieve such loading levels and positive electrode densities, and a positive electrode that satisfies the above range of loading levels and positive electrode densities is suitable for realizing high-capacity, high-energy-density lithium secondary batteries.

[0074] binder The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0075] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes in the battery that is constructed can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0076] The binder and conductive material content may be 0.5% to 5% by weight, respectively, based on 100% by weight of the positive electrode active material layer.

[0077] Al can be used as the positive electrode current collector, but it is not limited to this.

[0078] Lithium-ion battery One embodiment provides a lithium secondary battery including the positive electrode, negative electrode, and electrolyte described above.

[0079] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figure 1 is a schematic diagram showing a lithium secondary battery according to one embodiment. Referring to Figure 1, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown).

[0080] A lithium secondary battery according to one embodiment may be capable of being charged at a high voltage or suitable for being driven at a high voltage. For example, the charging voltage of the lithium secondary battery may be 4.45V or higher, and may be 4.45V to 4.7V, 4.45V to 4.6V, or 4.45V to 4.55V. By applying the positive electrode active material according to one embodiment, the amount of gas generated can be significantly reduced even when charged at a high voltage, and high capacity and long life characteristics can be achieved.

[0081] negative electrode The negative electrode may include a current collector and a negative electrode active material layer located on the current collector, the negative electrode active material layer comprising a negative electrode active material and further comprising a binder, a conductive material, or a combination thereof.

[0082] negative electrode active material The negative electrode active material includes a material capable of reversibly inserting / desorbing lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0083] Examples of the material capable of reversibly inserting / desorbing the lithium ions include carbon-based negative electrode active materials, which can include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0084] As the alloy of the lithium metal, 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.

[0085] As the material capable of doping and undoping lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), an 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. The Sn-based negative electrode active material can be Sn, SnO2, an Sn alloy, or a combination thereof.

[0086] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D) of the silicon-carbon composite particles. 50 The particle size can be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (core) formed by granulating primary silicon particles, and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0087] 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. The amorphous carbon may be soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0088] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10% to 50% by weight per 100% by weight of the silicon-carbon composite, and the amorphous carbon content may be 50% to 90% by weight. Furthermore, when the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10% to 50% by weight per 100% by weight of the silicon-carbon composite, the crystalline carbon content may be 10% to 70% by weight, and the amorphous carbon content may be 20% to 40% by weight.

[0089] Furthermore, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D) of the silicon particles (primary particles) 50) can be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, or in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon can be represented by SiO x (0 < x < 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation can 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.

[0090] 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 and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight.

[0091] binder The binder serves to make the negative electrode active material particles adhere well to each other and also make the negative electrode active material adhere well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0092] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0093] The aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylicated 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.

[0094] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0095] The dry binder is a polymeric substance that can be formed into fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0096] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes 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, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0097] The content of the negative electrode active material is 95% to 99.5% by weight relative to 100% by weight of the negative electrode active material layer, 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 material.

[0098] Current collector 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 alloys thereof, and may be in the form of 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.

[0099] electrolyte The electrolyte for lithium secondary batteries can be, for example, an electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0100] Non-aqueous organic solvents act as a medium through which ions involved in the electrochemical reactions of a battery can move. Non-aqueous organic solvents can be carbonate, ester, ether, ketone, or alcoholic solvents, aprotic solvents, or combinations thereof.

[0101] Examples of carbonate-based 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). Examples of ester-based solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone. As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran can be used. As ketone-based solvents, cyclohexanone can be used. As alcohol-based solvents, ethyl alcohol and isopropyl alcohol can be used, and as aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, and can include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes can be used.

[0102] Non-aqueous organic solvents can be used alone or in combination of two or more. When used in combination of two or more, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is generally understood by those working in this field.

[0103] When using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and these can be mixed in a volume ratio of 1:1 to 1:9.

[0104] Non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed and used in a volume ratio of 1:1 to 30:1.

[0105] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0106] Typical examples of the aforementioned ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0107] Lithium salts dissolve in organic solvents and act as a source of lithium ions within batteries, enabling the operation of basic lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical 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, and LiN(C x F 2x+1 SO2)(C y F 2y+1 It may contain one or more selected from SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0108] The lithium salt concentration is preferably within the range of 0.1 M to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate ionic conductivity and viscosity, resulting in excellent performance and effective lithium ion movement.

[0109] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers of these materials. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0110] The separator may include a porous substrate and a coating layer containing organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0111] The porous substrate may be a polymer film formed from one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon®, and polytetrafluoroethylene, or from a copolymer or mixture of two or more of these polymers.

[0112] The porous substrate can have a thickness of approximately 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.

[0113] The organic substance may include a (meth)acrylic copolymer comprising a first structural unit derived from (meth)acrylamide, a second structural unit comprising at least one of a first structural unit derived from (meth)acrylic acid or (meth)acrylate, and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0114] 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) of the inorganic particles is 50 The range is 1 nm to 2000 nm, and can be, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0115] The organic and inorganic materials may exist mixed together in a single coating layer, or they may exist in a form in which a coating layer containing organic materials and a coating layer containing inorganic materials are stacked on top of each other.

[0116] The thickness of the coating layer is 0.5 μm to 20 μm, and can be, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0117] The following describes examples and comparative examples of the present invention. The following examples are merely illustrative of the present invention and are not limited to the following examples.

[0118] Example 1 1. Manufacturing of positive electrode active material Ni 0.75 Mn 0.23 Al 0.02 (OH)2 and LiOH are mixed in a molar ratio of 1:1.05 and subjected to a first heat treatment at 850°C for 8 hours in an oxygen atmosphere, resulting in a composition of Li 1.05 Ni 0.75 Mn0.23 Al 0.02 It is O2 and the average particle size (D 50 A composite oxide in secondary particle form with a diameter of approximately 14 μm was fabricated.

[0119] After mixing aluminum sulfate with distilled water as a solvent, the prepared composite oxide was added and mixed for approximately 20 to 60 minutes. At this time, the aluminum content of the aluminum sulfate was designed to be 1.0 mol% relative to 100% by weight of the total metal excluding lithium in the final positive electrode active material. After removing the solvent from the mixed solution and drying at 190°C, zirconium oxide powder and magnesium oxide powder were dry-mixed into the obtained material, and a second heat treatment was performed at 825°C for 8 hours in an oxygen atmosphere to produce the final positive electrode active material. The zirconium content of the zirconium oxide was designed to be 0.2 mol% relative to 100% by weight of the total metal excluding lithium in the final positive electrode active material, and the magnesium content of the magnesium oxide was designed to be 0.1 mol% relative to 100% by weight of the total metal excluding lithium in the final positive electrode active material.

[0120] 2. Manufacturing of lithium-ion batteries A slurry of 98.5% by weight of the manufactured positive electrode active material, 1.0% by weight of polyvinylidene fluoride binder, and 0.5% by weight of carbon nanotube conductive material was mixed to produce a positive electrode active material layer slurry. This slurry was then coated onto an aluminum foil current collector, dried, and rolled to produce the positive electrode. At this time, the loading level of the positive electrode active material layer was 10 mg / cm². 2 The density of the final rolled positive electrode was approximately 3.4 g / cc.

[0121] A negative electrode active material layer slurry was prepared by mixing 97.5% by weight of graphite negative electrode active material, 1.5% by weight of carboxymethylcellulose, and 1% by weight of styrene-butadiene rubber in an aqueous solvent. The negative electrode active material layer slurry was coated onto a copper foil current collector, and the negative electrode was prepared by drying and rolling.

[0122] A lithium secondary battery was manufactured using a conventional method, employing a polytetrafluoroethylene separator and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent containing a 3:7 volume ratio mixture of ethylene carbonate and dimethyl carbonate.

[0123] Example 2 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the magnesium content of the magnesium oxide was designed and mixed so that it was 0.2 mol% relative to 100% by weight of the total metals excluding lithium in the final positive electrode active material.

[0124] Example 3 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the magnesium content of the magnesium oxide was designed and mixed so that it was 0.4 mol% relative to 100% by weight of the total metals excluding lithium in the final positive electrode active material.

[0125] Example 4 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 2, except that the zirconium content of the zirconium oxide was designed and mixed so that it was 0.4 mol% relative to 100% by weight of the total metals excluding lithium in the final positive electrode active material.

[0126] Comparative Example 1 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that magnesium oxide powder was not added to the positive electrode active material and Mg was not coated.

[0127] Comparative Example 2 The positive electrode active material was prepared in substantially the same manner as in Example 1, except that it was dry-coated with aluminum and Zr and Mg were not coated. In other words, the composition was Li 1.05 Ni 0.75Mn 0.23 Al 0.02 A composite oxide in the form of secondary particles of O2 and aluminum oxide powder were mixed and heat-treated in an oxygen atmosphere at 825°C for 8 hours to produce a dry-coated Al positive electrode active material. A lithium secondary battery was manufactured in substantially the same manner as in Example 1, except that this was used as the positive electrode active material.

[0128] Comparative Example 3 Ni 0.75 Mn 0.25 (OH)2, LiOH, and Al2O3 are mixed in a molar ratio of 1:1:0.02 and heat-treated at 850°C for 8 hours in an oxygen atmosphere to obtain an average particle size (D 50 A composite oxide doped with aluminum in secondary particle form, with a particle size of approximately 14 μm, was prepared. The prepared aluminum-doped composite oxide and aluminum oxide powder were mixed and heat-treated in an oxygen atmosphere at 825°C for 8 hours to produce a dry-coated positive electrode active material. A lithium secondary battery was manufactured in substantially the same manner as in Example 1, except that this was used as the positive electrode active material.

[0129] Comparative Example 4 Ni 0.75 Mn 0.25 (OH)2, LiOH, and Al2O3 are mixed in a molar ratio of 1:1:0.02 and heat-treated at 850°C for 8 hours in an oxygen atmosphere to obtain an average particle size (D 50 A composite oxide doped with aluminum in secondary particle form, with a particle size of approximately 14 μm, was prepared. A lithium secondary battery was prepared in substantially the same manner as in Example 1, except that this was used as the positive electrode active material.

[0130] Comparative Example 5 Ni 0.75 Mn 0.25 (OH)2 and LiOH are mixed in a 1:1 molar ratio and heat-treated at 850°C for 8 hours in an oxygen atmosphere to obtain a composition of LiNi 0.75 Mn 0.25 It is O2 and the average particle size (D 50A composite oxide in the form of secondary particles with a diameter of approximately 14 μm was manufactured. A lithium secondary battery was manufactured in substantially the same manner as in Example 1, except that this was used as the positive electrode active material.

[0131] To aid understanding, Table 1 below briefly shows the design details of the positive electrode active materials for the examples and comparative examples.

[0132] [Table 1]

[0133] Evaluation Example 1: Evaluation of Initial Charge / Discharge Capacity and Efficiency The lithium secondary batteries manufactured in Examples 1-4 and Comparative Examples 1-5 were charged at 25°C with a constant current of 0.2C to 4.45V and then with a constant voltage of 0.05C to perform initial charge and discharge. After that, they were discharged at 0.2C to a cutoff voltage of 3.0V. Table 1 above shows the initial charge capacity, initial discharge capacity, and the ratio of the latter to the former, calculated efficiently.

[0134] Evaluation Example 2: Lifetime Characteristics Following the initial charge and discharge cycle in Evaluation Example 1, the cycle of charging to 1.0C and discharging to 1.0C within a voltage range of 3.0V to 4.45V was repeated 25 or more times, and the ratio of the discharge capacity after 25 cycles to the initial discharge capacity was calculated and is shown in Table 1.

[0135] Evaluation Example 3: Evaluation of Gas Generation Amount After the batteries of Example 2 and Comparative Examples 1-5 were initially charged to 4.45V as in Evaluation Example 1, and then stored at 90°C for 4 hours, the amount of gas generated inside the batteries was measured, and the results are shown in Table 1.

[0136] Referring to Table 1, it was found that in Examples 1 to 4, the initial charge / discharge capacity and efficiency under high voltage conditions were maintained at a high level while the life characteristics were improved, and the amount of gas generated under high temperature conditions was significantly reduced.

[0137] In Comparative Example 1, where the Mg coating was omitted, the lifetime performance at high voltage was slightly reduced, and the amount of gas generated at high temperatures was higher than in the Examples. In Comparative Example 2, where the Zr and Mg coatings were omitted and Al was dry-coated, the lifetime performance at high voltage was significantly reduced, and the amount of gas generated at high temperatures was higher than in the Examples. In Comparative Example 3, where Al was separately doped during the synthesis of the core particles, the Zr and Mg coatings were omitted, and Al was dry-coated, the initial discharge capacity and charge / discharge efficiency at high voltage decreased, the lifetime performance was significantly lower, and the amount of gas generated at high temperatures was high. In Comparative Example 4, where Al was separately doped during the synthesis of the core particles, and the Al, Zr, and Mg coatings were omitted, the lifetime performance at high voltage was reduced, and the amount of gas generated at high temperatures was significantly higher. In Comparative Example 5, where Al was not introduced into the core particles and the Al, Zr, and Mg coatings were omitted, the lifetime performance at high voltage was significantly reduced, and the amount of gas generated at high temperatures was too high to be commercially viable.

[0138] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art that utilize the basic concepts defined in the claims also fall within the scope of the present invention. [Explanation of Symbols]

[0139] 100 Lithium-ion rechargeable batteries 10 positive electrode 20 negative electrode 30 Separators 40 Electrode assembly 50 cases

Claims

1. Core particles containing lithium nickel-manganese composite oxide, wherein the nickel content is 60 mol% or more and the manganese content is 10 mol% to 40 mol%, relative to 100 mol% of the total metal excluding lithium, and The coating layer located on the surface of the core particles contains Al, Zr, and Mg, A positive electrode active material wherein the Al content of the coating layer is 0.1 mol% to 2 mol%, the Zr content of the coating layer is 0.1 mol% to 0.4 mol%, and the Mg content of the coating layer is 0.1 mol% to 0.5 mol%.

2. The positive electrode active material according to claim 1, wherein the ratio of Zr and Mg content to Al content in the coating layer is 0.1 to 0.

65.

3. The positive electrode active material according to claim 1, wherein the coating layer is in the form of a shell that continuously surrounds the surface of the core particles.

4. The positive electrode active material according to claim 1, wherein the thickness of the coating layer is 5 nm to 500 nm.

5. The positive electrode active material according to claim 1, wherein the coating layer further comprises nickel, manganese, or a combination thereof.

6. The positive electrode active material according to claim 1, wherein the lithium nickel-manganese composite oxide of the core particles has a nickel content of 60 mol% to 80 mol% relative to 100 mol% of the total metal excluding lithium.

7. The lithium nickel-manganese composite oxide of the core particles is a lithium nickel-manganese-aluminum composite oxide that further contains aluminum in addition to nickel and manganese. The positive electrode active material according to claim 1, wherein the aluminum content in the lithium nickel-manganese-aluminum composite oxide is 1 mol% to 3 mol% relative to 100 mol% of the total metal excluding lithium.

8. The lithium nickel-manganese composite oxide of the core particles is represented by the following chemical formula 1, and is the positive electrode active material according to claim 1: [Chemical formula 1] Li a1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≦ a1 ≦ 1.8, 0.6 ≦ x1 ≦ 0.8, 0.1 ≦ y1 ≦ 0.4, 0 ≦ z1 ≦ 0.03, 0 ≦ w1 ≦ 0.3, 0.9 ≦ x1 + y1 + z1 + w1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1 is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zr, and X is one or more elements selected from F, P, and S.

9. The positive electrode active material according to claim 8, wherein in the chemical formula 1, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 ≤ z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.

29.

10. The positive electrode active material according to claim 1, wherein the cobalt content is 0 mol% to 0.01 mol% relative to 100 mol% of the total metal excluding lithium.

11. The positive electrode active material according to claim 1, wherein the core particles are in the form of secondary particles formed by the aggregation of a plurality of primary particles.

12. The positive electrode active material according to claim 11, further comprising a grain boundary coating portion containing Al, located on the surface of a primary particle inside the secondary particle.

13. The positive electrode active material according to claim 12, wherein the Al content in the grain boundary coating portion is less than the Al content in the coating layer.

14. The positive electrode active material according to claim 12, wherein the grain boundary coating portion further contains Mg.

15. The average particle size (D) of the positive electrode active material 50 The positive electrode active material according to claim 1, wherein the diameter is 10 μm to 18 μm.

16. The positive electrode active material according to claim 1, wherein the positive electrode active material does not contain sodium.

17. A nickel-manganese composite hydroxide having a nickel content of 60 mol% or more and a manganese content of 10 mol% to 40 mol% relative to 100 mol% of the total metal is mixed with a lithium raw material and subjected to a first heat treatment to obtain a lithium nickel-manganese composite oxide. After adding the obtained lithium nickel-manganese composite oxide to a solution in which Al raw materials were mixed in an aqueous solvent and mixing, the mixture was dried. A method for producing a positive electrode active material, comprising dry mixing the obtained material with a Zr raw material and an Mg raw material and performing a second heat treatment to obtain a positive electrode active material.

18. The Al content in the aforementioned Al raw material is 0.1 mol% to 2 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material. The Zr content in the Zr raw material is 0.1 mol% to 0.4 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material. The method for producing a positive electrode active material according to claim 17, wherein the Mg content in the Mg raw material is 0.1 mol% to 0.5 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material.

19. The aforementioned Al raw material includes aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum hydroxide, or a combination thereof. The Zr raw material includes zirconium oxide, zirconium silicate, or a combination thereof. The method for producing a positive electrode active material according to claim 17, wherein the Mg raw material includes magnesium oxide, magnesium phosphate, magnesium carbonate, or a combination thereof.

20. The method for producing a positive electrode active material according to claim 17, wherein the solution obtained by mixing an aluminum raw material with the aqueous solvent has a pH of 1.5 to 3.

5.

21. The first heat treatment is performed at 750°C to 950°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 850°C.

22. The method for producing a positive electrode active material according to claim 17, wherein the nickel-manganese composite hydroxide is a nickel-manganese-aluminum composite hydroxide further containing aluminum, and the aluminum content in the lithium nickel-manganese-aluminum composite hydroxide is 1 mol% to 3 mol% based on 100 mol% of the total metal.

23. Positive electrode current collector, and The positive electrode active material layer located on the positive electrode current collector is included, The positive electrode comprises the positive electrode active material layer according to any one of claims 1 to 16.

24. The positive electrode according to claim 23, Negative electrode, and A lithium-ion secondary battery containing an electrolyte.

25. A lithium secondary battery according to claim 24, wherein the charging voltage is 4.45V or higher.

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