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 containing lithium nickel manganese composite oxide, in which the economic efficiency, high capacity, and long life are secured and the high-voltage characteristic and the high-temperature characteristic are improved, a manufacturing method for the positive electrode active material, a positive electrode including the positive electrode active material, and a lithium secondary battery.SOLUTION: A positive electrode active material includes a core particle containing layered lithium nickel manganese composite oxide, a first coating layer existing on a surface of the core particle and containing Al, and a second coating layer existing on the first coating layer and containing Ni. A manufacturing method for the positive electrode active material, a positive electrode including the positive electrode active material, and a lithium secondary battery 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; 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 positive electrode active material including core particles containing a layered lithium nickel-manganese composite oxide, a first coating layer containing Al and located on the surface of the core particles, and a second coating layer containing Ni and located on the first coating layer.

[0006] In another embodiment of the present invention, there is provided a method for manufacturing a positive electrode active material, including mixing a layered nickel-manganese composite hydroxide and a lithium raw material, performing a first heat treatment to obtain a lithium nickel-manganese composite oxide, introducing an Al raw material into an aqueous solvent, introducing and mixing the lithium nickel-manganese composite oxide, then introducing a Ni raw material and mixing, drying this, and performing a second heat treatment.

[0007] In another embodiment of the present invention, there is provided a positive electrode including 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 contains the positive electrode active material described above.

[0008] In another embodiment of the present invention, there is provided a lithium secondary battery including the positive electrode, a negative electrode, and an electrolyte.

Advantages of the Invention

[0009] [[ID=I8]] The positive electrode 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 positive electrode active material can exhibit high initial charge-discharge capacity and efficiency even under high-voltage driving conditions, can realize long-life characteristics, and can effectively suppress the problem of gas generation 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. [Figure 2] It is a cross-sectional view schematically showing a lithium secondary battery according to one embodiment. [Figure 3]This is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 4] This is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 5] This is an HR-STEM image of the cross-section of the positive electrode active material in Example 1. [Figure 6] This is an EDS (Energy Dispersive X-ray Spectrometry) analysis image showing Ni highlighted in the cross-section of the positive electrode active material of Example 1. [Figure 7] This is an EDS analysis image showing Al highlighted in the cross-section of the positive electrode active material of Example 1. [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 indicated 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 transmission electron microscopy or scanning electron microscopy. 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 is the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50% by volume. 50 ) means. Also, unless otherwise defined, the average particle size is the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50% by volume, obtained by measuring the size (diameter or length of the long axis) of more than 20 randomly selected particles from a scanning electron microscope image. 50 This could be the average particle size taken from ).

[0018] Here, "or" is not interpreted as having an exclusive meaning; 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 In one embodiment, a positive electrode active material is provided, comprising core particles containing a layered lithium nickel-manganese composite oxide, a first coating layer containing Al located on the surface of the core particles, and a second coating layer containing Ni located on the first coating layer.

[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. In addition, 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 positive electrode active material is provided that maximizes capacity and efficiency by introducing a first coating layer and a second coating layer on the surface of core particles containing a layered lithium nickel-manganese composite oxide, thereby reducing gas generation even under high voltage and high temperature conditions and achieving long-life characteristics.

[0023] core particle The core particles contain a lithium nickel-manganese composite oxide, and the nickel content is 60 mol% relative to 100 mol% of the total metal excluding lithium in the lithium nickel-manganese composite oxide. For example, it may be 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.

[0024] The manganese content is, for example, 10 mol% or more 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 40 mol%, 15 mol% to 35 mol%, 15 mol% to 30 mol%, 20 mol% to 30 mol%, 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 1.5 mol% to 2.5 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-based 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 aggregated from a plurality of primary particles, and 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 absent or present in a very small amount, a stable layered structure can be maintained, aluminum by-products or aluminum aggregates do not occur, and the capacity, efficiency, and life characteristics of the positive electrode active material can be improved simultaneously.

[0027] The lithium nickel-manganese-based composite oxide is specifically represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 Mn y1 Al<00000q6> 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 ≤ w_1 ≤ 0.29 can be satisfied. For example, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 < z1 ≤ 0.03, and 0 ≤ w_1 ≤ 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, 0 ≤ w_1 ≤ 0.28, 0 ≤ w_1 ≤ 0.27, 0 ≤ w_1 ≤ 0.26, 0 ≤ w_1 ≤ 0.25, 0 ≤ w_1 ≤ 0.24, 0 ≤ w_1 ≤ 0.23, 0 ≤ w_1 ≤ 0.22, 0 ≤ w_1 ≤ 0.21, 0 ≤ w_1 ≤ 0.2, 0 ≤ w_1 ≤ 0.15, 0 ≤ w_1 ≤ 0.1, or 0 ≤ w_1 ≤ 0.09 etc. may hold.

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

[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] First coating layer The Al content in the first 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 first coating layer, separate from the aluminum contained in the core particles. The aluminum content in the first 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 first coating layer satisfies 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 first 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 first coating layer is too low, a coating layer of appropriate thickness may not be formed, reducing the effect of suppressing side reactions with the electrolyte.

[0035] The first coating layer may be in the form of a film that continuously surrounds the surface of the core particle, for example, it may be in the form of a shell that surrounds the entire surface of the core particle. This is distinct from a structure in which only a part of the core particle surface is partially coated. According to one embodiment, the first coating layer may be formed in a form that completely surrounds the surface of the core particle, yet be very thin and uniform in thickness. As a result, the positive electrode active material does not experience increased resistance or decreased capacity, 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.

[0036] The thickness of the first coating layer is 5 nm to 40 nm, and may be, for example, 5 nm to 30 nm or 5 nm to 20 nm. When the first coating layer satisfies the above thickness range, the coating can improve the structural stability of the positive electrode active material without increasing resistance or decreasing capacitance, and can effectively suppress side reactions with the electrolyte. The thickness of the coating layer can be measured by, for example, SEM, TEM, TOF-SIMS, XPS, or EDS analysis, and the thickness range of the coating layer may be measured by TEM-EDS line profile.

[0037] The first coating layer may be even thicker than the second coating layer, which will be described later.

[0038] The first coating layer is characterized by being thin, at the level of tens to hundreds of nanometers, and having a uniform thickness. For example, the thickness deviation of the first 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 first 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.

[0039] The first coating layer may include, for example, aluminum oxide, lithium-aluminum oxide, or a combination thereof. The first coating layer may have a layered structure. That is, the compounds contained in the first coating layer may have a layered structure.

[0040] The first coating layer may also contain nickel, manganese, or a combination thereof, in addition to aluminum.

[0041] Second coating layer The Ni content in the second coating layer is 0.01 mol% to 1 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material, and can be, for example, 0.01 mol% to 0.9 mol%, 0.01 mol% to 0.7 mol%, 0.05 mol% to 0.5 mol%, or 0.1 mol% to 0.4 mol%. The Ni content in the second 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 Ni content in the second coating layer satisfies 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 Ni content of the second coating layer is too high, a uniform coating layer may not be formed, or the resistance may increase, leading to a decrease in charge-discharge efficiency and lifespan characteristics. Conversely, if the Ni content of the second coating layer is too low, a coating layer of appropriate thickness may not be formed, reducing the effect of suppressing side reactions with the electrolyte, or decreasing charge-discharge efficiency and high-temperature lifespan characteristics.

[0042] The second coating layer may be in the form of a film or shell that continuously surrounds the surface of the first coating layer. According to one embodiment, the second coating layer may be formed to completely surround the outermost surface of the positive electrode active material, yet be very thin and uniform in thickness. This prevents the positive electrode active material from experiencing increased resistance or decreased capacitance, improves structural stability, effectively suppresses side reactions with the electrolyte, reduces gas generation under high voltage and high temperature conditions, and enables long-life characteristics.

[0043] The thickness of the second coating layer is 10 nm or less, and may be, for example, 0.1 nm to 10 nm, 0.5 nm to 9 nm, 1 nm to 7 nm, or 1 nm to 5 nm. When the second coating layer satisfies the above thickness range, the coating can improve the structural stability of the positive electrode active material without increasing resistance or decreasing capacitance, and effectively suppress side reactions with the electrolyte. The thickness of the coating layer can be measured by, for example, SEM, TEM, TOF-SIMS, XPS, or EDS analysis, and the thickness range of the coating layer may be measured by TEM-EDS line profile.

[0044] The second coating layer is characterized by being thin, at the level of a few nanometers, and having a uniform thickness. For example, the deviation in the thickness of the second coating layer within a single positive electrode active material particle may be 20% or less, 18% or less, or 15% or less. Here, the deviation in the thickness of the coating layer refers to the content of the thickness of the coating layer within a single positive electrode active material particle. The deviation in the thickness 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 deviation or standard deviation of the thickness of the second coating layer satisfies the above range, it means that a coating layer of uniform thickness is well formed in film form on the outermost 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.

[0045] The second coating layer may further contain Al in addition to Ni. The second coating layer may include, for example, nickel oxide, lithium-nickel oxide, aluminum-nickel oxide, lithium-aluminum-nickel oxide, or a combination thereof. The second coating layer may have a layered structure. Having a layered crystalline structure for the core, the first coating layer, and the second coating layer can further promote lithium insertion and removal.

[0046] On the other hand, the first coating layer may be even thicker than the second coating layer. For example, the ratio of the thickness of the second coating layer to the thickness of the first coating layer is less than 0.5, and may be, for example, 0.4 or less, or 0.3 or less. When the thicknesses of the first and second coating layers satisfy this relationship, the structural stability of the positive electrode active material can be improved without the coating increasing resistance or decreasing capacitance, and side reactions with the electrolyte can be effectively suppressed to improve high-voltage and high-temperature characteristics.

[0047] The Al content of the first coating layer may be even greater than the Ni content of the second coating layer. Here, "content" refers to the molar content, meaning the molar content relative to 100 mol% of the metal excluding lithium in the positive electrode active material. For example, the ratio of the Ni content of the second coating layer to the Al content of the first coating layer is less than 0.5, and may be, for example, 0.4 or less, or 0.3 or less. When the Al content of the first coating layer and the Ni content of the second coating layer satisfy this relationship, the structural stability of the positive electrode active material can be improved without increasing resistance or decreasing capacitance due to the coating, and side reactions with the electrolyte can be effectively suppressed, thereby improving high-voltage and high-temperature characteristics.

[0048] grain boundary coating section On the other hand, during the formation of the first coating layer, aluminum can diffuse into the core particles. As a result, the positive electrode active material according to one embodiment may further include a grain boundary coating portion containing aluminum, located on the surface of the primary particles inside the secondary particles. Here, the secondary particles refer to the core particles, and the interior of the secondary particles refers to the entire interior excluding the surface of the secondary particles, or it can refer to the region from the surface of the secondary particles toward the center of the secondary particles up to approximately 60% of the radius. The grain boundary coating portion is a concept distinct from the coating layer on the surface of the core particles, and refers to a coating portion formed on the surface of the primary particles located inside the core particles. The presence of the grain boundary coating portion 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 portion further stabilizes the positive electrode active material structurally, improving its lifetime characteristics.

[0049] 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.

[0050] Furthermore, the grain boundary coating may contain nickel, manganese, yttrium, or a combination thereof, in addition to aluminum.

[0051] Average particle size of positive electrode active material according to one embodiment (D 50 The particle size is not particularly limited, but may be, for example, 1 μm to 25 μm, 5 μm to 20 μm, 10 μm to 20 μm, 11 μm to 18 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.

[0052] 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.

[0053] 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.

[0054] Method for manufacturing positive electrode active material In one embodiment, a method for producing a positive electrode active material is provided, which includes mixing a layered nickel-manganese composite hydroxide and a lithium raw material, performing a first heat treatment to obtain a lithium nickel-manganese composite oxide, adding an Al raw material to an aqueous solvent, adding and mixing the lithium nickel-manganese composite oxide, adding and mixing a Mn raw material, drying the mixture, and performing a second heat treatment. The above method can be used to produce the positive electrode active material described above.

[0055] The aforementioned layered nickel-manganese composite hydroxide is a precursor to core particles and may be in the form of secondary particles formed by the aggregation of multiple primary particles. It may contain no cobalt or only a very small amount of cobalt, for example, it may be a cobalt-free nickel-manganese composite hydroxide. Nickel-manganese-aluminum composite hydroxides can be produced by a conventional coprecipitation method.

[0056] In layered nickel-manganese composite hydroxides, the nickel content is 60 mol% or more relative to 100 mol% of the total metal, 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.

[0057] In layered nickel-manganese composite hydroxides, the manganese content is 10 mol% or more relative to 100 mol% of the total metal, and can be, for example, 10 mol% to 40 mol%, 15 mol% to 39 mol%, 15 mol% to 35 mol%, 15 mol% to 30 mol%, 20 mol% to 30%, etc.

[0058] Furthermore, if the layered nickel-manganese composite hydroxide further 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, high capacity can be achieved, the structural safety of the positive electrode active material can be improved, and production costs can be reduced, thereby improving economic efficiency.

[0059] In one embodiment of the method for producing a positive electrode active material, by not further doping with aluminum during the production of core particles and using an aluminum raw material during the production of the precursor, a nickel-manganese-aluminum composite hydroxide in which aluminum is uniformly dispersed within the structure can be used as the precursor. By using such a precursor, a positive electrode active material can be produced in which the layered structure is stably maintained even after repeated charging and discharging, without containing cobalt. This prevents the formation of aluminum by-products and aluminum aggregates, improving the capacity, efficiency characteristics, and lifespan characteristics of the positive electrode active material.

[0060] In layered 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.

[0061] A layered nickel-manganese composite hydroxide is, for example, represented by the following chemical formula 2. [Chemical formula 2] Ni x2 Mn y2 Al z2 M 2 w2 (OH)2

[0062] In chemical formula 2, 0.6 ≤ x² ≤ 0.8, 0.1 ≤ y² ≤ 0.40 ≤ 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.

[0063] 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.

[0064] Layered 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.

[0065] The layered 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 yields a lithium nickel-manganese composite oxide. The resulting composite oxide is substantially the same as the core particles described in the section on positive electrode active material.

[0066] Layered lithium nickel-manganese composite oxides differ considerably from existing nickel 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.

[0067] In one embodiment, an Al raw material is added to an aqueous solvent and mixed, then a layered lithium nickel-manganese composite oxide is added and mixed to induce a first coating layer on the surface of the layered lithium nickel-manganese composite oxide particles (core particles). Next, a Ni raw material is added to the mixed solution and mixed to induce a second coating layer. After that, the solvent is removed from the mixed solution and dried, followed by a second heat treatment to obtain a positive electrode active material in which an Al-containing first coating layer and a Ni-containing second coating layer are sequentially formed on the surface of the core particles. This can be described as a continuous wet coating method.

[0068] The aqueous solvent may include distilled water, an alcoholic solvent, or a combination thereof. The Al raw material may include, for example, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum hydroxide, or a combination thereof. As an example, the Al raw material may include aluminum sulfate, in which case it is advantageous to form a first coating layer having a uniform thickness on the surface of the lithium nickel-manganese composite oxide particles.

[0069] The Al raw material is a raw material for forming a coating layer, and the Al content in the Al 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 positive electrode 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 Al coating content within the above range, a first coating layer with a thin thickness of tens to hundreds of nanometers and uniform thickness can be formed, which can reduce the amount of gas generated in lithium secondary batteries under high voltage or high temperature operating conditions, improving high capacity and long life characteristics.

[0070] The solution obtained by adding the Al raw material to an aqueous solvent has a pH of 1.5 to 3.5, and can be, for example, 2.0 to 3.4, 2.5 to 3.3, 2.7 to 3.3, or 2.9 to 3.2. Adding and mixing the lithium nickel-manganese composite oxide to the aqueous solvent containing the aluminum raw material can be done for approximately 5 to 80 minutes, 5 to 60 minutes, or 5 to 40 minutes. The pH of the mixed solution after stirring is 4.5 to 8.5, and can 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 the formation of a first coating layer of uniform thickness.

[0071] The Ni raw material may include, for example, nickel nitrate, nickel sulfate, nickel carbonate, nickel hydroxide, or a combination thereof. The Ni content in the Ni raw material can be designed to be 0.01 mol% to 1 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material, for example, 0.01 mol% to 0.9 mol%, 0.01 mol% to 0.7 mol%, 0.05 mol% to 0.5 mol%, or 0.1 mol% to 0.4 mol%. By designing the Ni coating content within the above range, a second coating layer with a thin thickness of a few nanometers and uniform thickness can be formed, improving the performance of lithium secondary batteries under high voltage or high temperature operating conditions and enhancing high capacity and long life characteristics.

[0072] The Ni raw material can be added and mixed for approximately 5 to 80 minutes, 5 to 60 minutes, or 10 to 40 minutes. The pH of the final mixed solution after stirring is 4.5 to 8.5, and can 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 the formation of a second coating layer of uniform thickness.

[0073] Removing the solvent with the mixed solution and drying can be done, for example, at 40°C to 240°C, 100°C to 220°C, or 150°C to 200°C.

[0074] The second heat treatment can be performed, 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 second heat treatment temperature can be lower than the first heat treatment temperature, and the second heat treatment time is preferably the same as or shorter than the first heat treatment time. By performing the second heat treatment under these conditions, the desired coating layer can be obtained.

[0075] 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.

[0076] According to one embodiment, the loading level of the positive electrode active material layer is 10 mg / cm³. 2 ~40 mg / cm³ 2 It could be 10 mg / cm³, for example. 2 ~30 mg / cm³ 2 or 10 mg / cm³ 2 ~20 mg / cm³ 2 This is possible. Furthermore, the density of the positive electrode active material layer in the rolled final positive electrode can 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 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Al can be used as the positive electrode current collector, but it is not limited to this.

[0081] Lithium-ion battery In one embodiment, a lithium secondary battery is provided that includes the positive electrode, negative electrode, and electrolyte described above. As an example, the lithium secondary battery may include a positive electrode, a negative electrode, a separation membrane located between the positive electrode and the negative electrode, and an electrolyte.

[0082] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, where Figure 1 may be circular, Figure 2 rectangular, and Figures 3 and 4 pouch-type batteries. Referring to Figures 1 to 4, 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, negative electrode 20, and 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 Figure 1. Also, in Figure 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 Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for inducing the current formed in the electrode assembly 40 to the outside.

[0083] 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.

[0084] 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.

[0085] negative electrode active material The negative electrode active material includes a substance capable of reversibly inserting / de-inserting lithium ions, lithium metal, an alloy of lithium metal, a lithium-doped and de-doped substance, or a transition metal oxide.

[0086] Examples of the substance 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. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0087] 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.

[0088] As the substance 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.

[0089] The silicon-carbon composite can be a composite of silicon and amorphous carbon. The average particle size (D 50The 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.

[0090] 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.

[0091] 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.

[0092] 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 The size of the silicon particles may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist as silicon alone, as a silicon alloy, or as an oxidized form. The oxidized form of silicon is SiO xIt can be represented by (0 < x < 2). At this time, the ratio of the atomic content 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.

[0093] 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 ratio.

[0094] Binder The binder plays a role of making the negative electrode active material particles adhere well to each other and making 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.

[0095] 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. [[ID=…]]

[0096] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluorine rubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0109] 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.

[0110] 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).

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The organic material 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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 1:1 molar ratio and subjected to a first heat treatment at 850°C for 8 hours in an oxygen atmosphere, resulting in a composition of LiNi 0.75 Mn 0.23 Al 0.02 It is O2 and the average particle size (D50 A composite oxide in secondary particle form with a diameter of approximately 14 μm was fabricated.

[0122] 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 in the aluminum sulfate was designed to be 1.0 mol% relative to 100% by weight of the total metal excluding lithium in the final cathode active material. Next, nickel sulfate was added and mixed for approximately 10 to 40 minutes. At this time, the nickel content in the nickel sulfate was designed to be 0.2 mol% relative to 100% by weight of the total metal excluding lithium in the final cathode active material. After removing the solvent from the mixed solution and drying at 190°C, a second heat treatment was performed at 825°C for 8 hours in an oxygen atmosphere to produce the final cathode active material.

[0123] 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.

[0124] 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.

[0125] A lithium secondary battery was manufactured using a conventional method with 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.

[0126] Comparative Example 1 In the manufacturing of the positive electrode active material, the Al and Ni coating process is omitted, and LiNi 0.75 Mn 0.23 Al 0.02 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the O2 composite oxide itself was used as the positive electrode active material.

[0127] Comparative Example 2 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that only Al was dry-coated without Ni coating in the manufacturing of the positive electrode active material.

[0128] The Al dry coating method is as follows: The composition is LiNi 0.75 Mn 0.23 Al 0.02 A composite oxide in the form of secondary particles, which is O2, and aluminum oxide powder were mixed and heat-treated in an oxygen atmosphere at 825°C for 8 hours to obtain a dry-coated positive electrode active material.

[0129] Comparative Example 3 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that only Al was wet-coated without Ni coating in the manufacturing of the positive electrode active material.

[0130] In other words, aluminum sulfate was mixed with distilled water as a solvent, the composite oxide was added and mixed for about 20 to 60 minutes, then the solvent was removed and the mixture was dried at 190°C. A second heat treatment was then performed at 825°C for 8 hours in an oxygen atmosphere to produce the cathode active material according to Comparative Example 3.

[0131] Comparative Example 4 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that only Ni was wet-coated without Al coating in the manufacturing of the positive electrode active material.

[0132] In other words, a composite oxide was added to distilled water as a solvent, nickel sulfate was added and mixed for about 10 to 40 minutes, then the solvent was removed and the mixture was dried at 190°C. A second heat treatment was then performed at 825°C for 8 hours in an oxygen atmosphere to produce the cathode active material according to Comparative Example 4.

[0133] Evaluation Example 1: Analysis of Cathode Active Material The positive electrode active material particles produced in Example 1 were cut using a focused ion beam (FIB) apparatus, and EDS and HR-STEM analysis were performed on the cross-section. Figure 5 is an HR-STEM image of the cross-section of the positive electrode active material in Example 1, and is a magnified image of the primary particles located on the outermost surface of the cross-section of the secondary particles. Figure 6 is an image in Figure 5 with the nickel element highlighted by EDS analysis, and Figure 7 is an image in Figure 5 with the aluminum element highlighted by EDS analysis. Referring to Figures 5 to 7, it can be confirmed that a first coating layer containing Al is formed on the surface of the secondary particles with a uniform thickness, and a second coating layer containing Ni is formed on the first coating layer in a thin, uniform film form, resulting in the formation of an overall uniform double coating layer and the production of a positive electrode active material with a double core-shell structure.

[0134] Evaluation Example 2: Charge / Discharge Characteristics and High-Temperature Life Characteristics The lithium secondary batteries manufactured in Example 1 and Comparative Examples 1-4 were charged to 4.45V with a constant current of 0.2C at 25°C, then to 0.05C with a constant voltage, and finally discharged to 3.0V at 0.2C to perform initial charge and discharge. The initial discharge capacities are shown in Table 1 below.

[0135] Next, the battery was charged to 1.0C and discharged to 1.0C at 45°C in a voltage range of 3.0V to 4.45V for more than 25 cycles. The ratio of the discharge capacity after 25 cycles to the initial discharge capacity was calculated and expressed as the high-temperature life in Table 1 below.

[0136] [Table 1]

[0137] Referring to Table 1, it can be confirmed that the lithium secondary battery of Example 1 is even superior to Comparative Examples 1-4 in terms of initial discharge capacity and life characteristics.

[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 11 Positive lead tab 12 Positive terminal 20 negative electrode 21 Negative lead tab 22 Negative terminal 30 Separators 40 Electrode assembly 50 cases 60 Sealing member 70 Electrode Tabs 71 Positive Tab 72 Negative Electrode Tabs

Claims

1. Core particles containing layered lithium nickel-manganese composite oxide, A first coating layer containing Al is located on the surface of the core particles, and It comprises a second coating layer located on a first coating layer and containing Ni, A positive electrode active material comprising a layered lithium nickel-manganese composite oxide of core particles, wherein the cobalt content is 0 mol% to 0.01 mol% relative to 100 mol% of the total metal excluding lithium.

2. The positive electrode active material according to claim 1, wherein the core particles are a layered lithium nickel-manganese composite oxide, the nickel content is 60 mol% to 80 mol% relative to 100 mol% of the total metal excluding lithium, and the manganese content is 10 mol% or more.

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

4. The layered lithium nickel-manganese composite oxide of the core particles is represented by 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.

5. The positive electrode active material according to claim 1, wherein the first coating layer and the second coating layer are in a continuous film form.

6. The thickness of the first coating layer is 5 nm to 40 nm. The positive electrode active material according to claim 1, wherein the thickness of the second coating layer is 10 nm or less.

7. The positive electrode active material according to claim 1, wherein the ratio of the thickness of the second coating layer to the thickness of the first coating layer is less than 0.

5.

8. The Al content of the first 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. The positive electrode active material according to claim 1, wherein the Ni content of the second coating layer is 0.01 mol% to 1 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material.

9. The Al content of the first coating layer is 0.5 mol% to 1.5 mol% relative to 100 mol% of the total metal content of the positive electrode active material excluding lithium. The positive electrode active material according to claim 1, wherein the Ni content of the second coating layer is 0.05 mol% to 0.5 mol% based on 100 mol% of the total metal excluding lithium in the positive electrode active material.

10. The positive electrode active material according to claim 1, wherein the ratio of the Ni content of the second coating layer to the Al content of the first coating layer is less than 0.

5.

11. The first coating layer comprises aluminum oxide, lithium-aluminum oxide, or a combination thereof. The positive electrode active material according to claim 1, wherein the second coating layer comprises nickel oxide, lithium-nickel oxide, aluminum-nickel oxide, lithium-aluminum-nickel oxide, or a combination thereof.

12. The positive electrode active material according to claim 1, wherein the first coating layer and the second coating layer have a layered structure.

13. The aforementioned core particle is a secondary particle form formed by the aggregation of multiple primary particles. The positive electrode active material according to claim 1, further comprising a grain boundary coating portion containing Al, located on the surface of a primary particle inside the secondary particle.

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

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 20 μm.

16. A layered nickel-manganese composite hydroxide and a lithium raw material are mixed and subjected to a first heat treatment to obtain a layered lithium nickel-manganese composite oxide. Al raw material is added to an aqueous solvent, then the lithium nickel-manganese composite oxide is added and mixed, and then Ni raw material is added and mixed. A method for producing a positive electrode active material, comprising drying it and performing a second heat treatment.

17. A method for producing a positive electrode active material according to claim 16, wherein the layered nickel-manganese composite hydroxide has a nickel content of 60 mol% to 80 mol%, a manganese content of 10 mol% or more, an aluminum content of 0 mol% to 3 mol%, and a cobalt content of 0 mol% to 0.01 mol% based on 100 mol% of the total metal.

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 aforementioned positive electrode active material. The method for producing a positive electrode active material according to claim 16, wherein the Ni content in the Ni raw material is 0.01 mol% to 1 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 method for producing a positive electrode active material according to claim 16, wherein the Ni raw material includes nickel nitrate, nickel sulfate, nickel carbonate, nickel hydroxide, or a combination thereof.

20. The method for producing a positive electrode active material according to claim 16, wherein the solution obtained by adding an Al raw material to 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 16, wherein the second heat treatment is performed at 700°C to 850°C.

22. 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 15.

23. The loading level of the positive electrode active material layer is 10 mg / cm². 2 ~40 mg / cm³ 2 The positive electrode according to claim 22.

24. The positive electrode according to claim 22, wherein the density of the positive electrode active material layer is 3.3 g / cc to 3.7 g / cc.

25. The positive electrode according to claim 22, Negative electrode, and A lithium-ion secondary battery containing an electrolyte.

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

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