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

Abstract

To provide a positive electrode active material for a lithium secondary battery capable of securing high energy density and long life characteristics while securing price competitiveness by minimizing cobalt content, and to provide a positive electrode and a lithium secondary battery including the same.SOLUTION: A positive active material for a rechargeable lithium battery, the positive active material being a bimodal type including a first lithium nickel-based composite oxide of large particles and a second lithium nickel-based composite oxide of small particles, the first and second lithium nickel-based composite oxides including nickel in an amount of greater than or equal to about 80 mol% based on 100 mol% of total metals excluding lithium, the ratio of the weight (A) of the first lithium nickel-based composite oxides to the weight (B) of the second lithium nickel-based composite oxides in the positive electrode active material is 1 to 4, the span {(D90 - D10) / D50} of the first lithium nickel-based composite oxides is 0.9 to 1.2, the span of the second lithium nickel-based composite oxides is 0.9 to 1.2, and the span of the positive electrode active material is 1.5 to 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Lithium secondary batteries are widely used as power sources for mobile information terminals such as smartphones and laptops, as they offer high energy density and are easy to carry. Recently, there has been active research into lithium secondary batteries that offer high safety and high capacity for use as power sources for hybrid and electric vehicles, as well as for power storage.

[0003] Among them, lithium cobalt oxides, such as LiCo2, are the most widely used cathode active materials. However, the uneven distribution and scarcity of cobalt resources increases manufacturing costs and poses challenges to stable supply.

[0004] Therefore, instead of expensive cobalt materials, we are developing a positive electrode active material made of lithium nickel composite oxide.

[0005] However, although lithium nickel-based composite oxides are inexpensive and have little metal toxicity, and can provide high capacity, they have the disadvantages of being difficult to synthesize as powder and having poor life characteristics. Summary of the Invention [Problem to be solved by the invention]

[0006] One embodiment provides a positive electrode active material for a lithium secondary battery that can minimize the cobalt content to ensure price competitiveness while simultaneously ensuring high energy density and long life characteristics.

[0007] Another embodiment is directed to providing a positive electrode and a lithium secondary battery comprising the positive electrode active material. [Means for solving the problem]

[0008] In one embodiment, the positive electrode active material is a bimodal type positive electrode active material including a first lithium-nickel-based composite oxide that is a large particle and a second lithium-nickel-based composite oxide that is a small particle, wherein the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide have a nickel content of 80 mol% or more relative to 100 mol% of all metals excluding lithium, and the ratio (A / B) of the weight (A) of the first lithium-nickel-based composite oxide to the weight (B) of the second lithium-nickel-based composite oxide in the positive electrode active material is 1 to 4, and the span (D 90 -D 10 ) / D 50} is 0.9 to 1.2, the span of the second lithium nickel composite oxide is 0.9 to 1.2, and the span of the positive electrode active material is 1.5 to 2.

[0009] In another embodiment, there is provided a positive electrode for a lithium secondary battery, comprising: a positive electrode current collector; and a positive electrode active material layer located on at least one surface of the positive electrode current collector and comprising the above-described positive electrode active material.

[0010] In yet another embodiment, a lithium secondary battery is provided that includes the aforementioned positive electrode, negative electrode, and electrolyte. [Effects of the Invention]

[0011] The positive electrode active material for a lithium secondary battery according to an embodiment minimizes the cobalt content to ensure price competitiveness, while at the same time improving high energy density and long life characteristics. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 2] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 3]1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 4] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 5] 1 compares the distribution of active material precursor or active material powder produced in continuous and batch reactors. [Figure 6] 1 is an SEM photograph of the surface of the first lithium nickel composite oxide, which is the large particle (A) produced in Production Example 1. [Figure 7] 1 is an image in which the aluminum element is highlighted by SEM-EDS analysis of the fracture surface of the first lithium nickel composite oxide, which is the large particle (A) of Production Example 1. [Figure 8] 1 is an image in which the cobalt element is highlighted by SEM-EDS analysis of a fracture surface of the first lithium nickel composite oxide, which is a large particle (A) of Production Example 1. [Figure 9] 1 is an SEM photograph of the surface of the first lithium nickel composite oxide, which is large particle (B) produced in Production Example 2. [Figure 10] 1 is an SEM photograph of the surface of the second lithium nickel composite oxide, which is a small particle produced in Production Example 3. [Figure 11] 1 shows particle size distribution graphs for the lithium nickel composite oxides produced in Production Examples 1 to 3 and the positive electrode active materials produced in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] Although the present invention may be embodied in many different forms, it is not limited to the embodiments set forth herein.

[0014] The terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

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

[0016] It should be understood that the terms "comprises," "includes," or "has" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0017] In the drawings, the thickness of various layers and regions is exaggerated for clarity, and similar parts are designated by the same reference numerals throughout the specification. When a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly on" another part, but also the case where there is another part between them. Conversely, when a part is said to be "directly on" another part, it means that there is no other part between them.

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

[0019] Average particle size (D 50 ) can be measured by methods well known to those skilled in the art, for example, by using a particle size analyzer or by using a transmission electron microscope image or a scanning electron microscope image. Another method is to measure using a dynamic light scattering method, and then perform data analysis to count the number of particles for each particle size range, and then calculate the average particle size (D 50) value can be obtained. Unless otherwise defined, the average particle size can mean the diameter of particles whose cumulative volume is 50% by volume in the particle size distribution. Also, unless otherwise defined, the average particle size is determined by measuring the size (diameter or major axis length) of 20 or more particles randomly in a scanning electron microscope image to obtain a particle size distribution, and then calculating the diameter of particles whose cumulative volume is 50% by volume in the particle size distribution as the average particle size (D 50 ) can be taken as

[0020] Also, "D 10 " means the average diameter of particles whose cumulative volume corresponds to 10% by volume in the particle size distribution, and "D90" means the average diameter of particles whose cumulative volume corresponds to 90% by volume in the particle size distribution.

[0021] Here, "or" is not to be construed in an exclusive sense; for example, "A or B" is to be construed as including A, B, A+B, etc.

[0022] The term "metal" is understood to include general metals, transition metals, and metalloids.

[0023] positive electrode active material In one embodiment, a bimodal type positive electrode active material is provided that includes a first lithium-nickel based composite oxide that is a large particle and a second lithium-nickel based composite oxide that is a small particle.

[0024] The large particles and small particles are each an average particle size (D 50 ) can be classified according to their range.

[0025] The large particles have a larger average particle size (D 50) may refer to a lithium-nickel-based composite oxide having a large particle size. In one embodiment, large particles may refer to a lithium-nickel-based composite oxide having an average particle size of 10 μm to 25 μm, and small particles may refer to a lithium-nickel-based composite oxide having an average particle size of 2 μm to 9 μm. Here, the terms "first lithium-nickel-based composite oxide" and "second lithium-nickel-based composite oxide" are used to distinguish between large particles having an average particle size of 10 μm to 25 μm and small particles having an average particle size of 2 μm to 9 μm, and do not necessarily indicate that the remaining properties, excluding the average particle size, are different. In other words, the remaining properties, excluding the average particle size, of the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide may be the same or different from each other.

[0026] In each of the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide, the nickel content is 80 mol % or more relative to 100 mol % of all metals excluding lithium, and the ratio (A / B) of the weight (A) of the first lithium-nickel-based composite oxide to the weight (B) of the second lithium-nickel-based composite oxide in the positive electrode active material is 1 to 4. 90 -D 10 ) / D 50} is 0.9 to 1.2, the span of the second lithium nickel composite oxide is 0.9 to 1.2, and the span of the positive electrode active material is 1.5 to 2.

[0027] In one embodiment, the positive electrode active material is a bimodal type including a first lithium-nickel-based composite oxide, which is a large particle, and a second lithium-nickel-based composite oxide, which is a small particle. By designing the particle size distribution of the large and small particles, the cobalt content can be minimized to ensure price competitiveness while simultaneously ensuring high energy density and long life characteristics.

[0028] The first lithium-nickel composite oxide and the second lithium-nickel composite oxide may be high-nickel composite oxides containing a high content of nickel. In the first lithium-nickel composite oxide and the second lithium-nickel composite oxide, the nickel content relative to 100 mol% of all metals excluding lithium is 80 mol% or more, for example, 85 mol% or more or 90 mol% or more. The upper limit is not specifically limited, but may be, for example, less than 100 mol%, 99.9 mol% or less, 99 mol% or less, 97 mol% or less, or 95 mol% or less. When the nickel content of the first lithium-nickel composite oxide and the second lithium-nickel composite oxide satisfies the above range, high capacity can be achieved and structural stability can be improved even when the cobalt content is reduced.

[0029] Batch reactors have traditionally been used to manufacture cathode active materials or their precursors. In a batch reactor, a portion of the reactants is pre-loaded into the reactor to control the reaction heat and adjust the reactant concentration, and the other components are added while stirring and reacting. A batch reactor has a raw material inlet that allows the raw materials to be continuously supplied as the reaction proceeds, and once the reaction is complete, the product is collected all at once. Therefore, batch reactors can economically produce uniform products without deviation because the reaction conditions, such as the concentration, temperature, and residence time of all reactants in the reactor, are the same. They are also characterized by a narrow particle size distribution, as shown in Figure 5.

[0030] On the other hand, in the case of a continuous stirred-tank reactor (CSTR), raw materials are fed and products are discharged simultaneously and continuously, so there is a deviation in the residence time and reaction time of the active material precursor and active material produced in the reactor, resulting in a wide particle size distribution as shown in Figure 5.

[0031] According to an embodiment, the first lithium-nickel-based composite oxide may be produced in a continuous reactor, and the second lithium-nickel-based composite oxide may be produced in a batch reactor.

[0032] The positive electrode active material can have improved high energy density and long life characteristics by mixing the first lithium-nickel-based composite oxide, which is a large particle produced in a continuous reactor, and the second lithium-nickel-based composite oxide, which is a small particle produced in a batch reactor, in an appropriate weight ratio.

[0033] The ratio (A / B) of the weight (A) of the first lithium-nickel composite oxide to the weight (B) of the second lithium-nickel composite oxide in the positive electrode active material may be within a range of 1 to 4. This ratio refers to the ratio of the weight (A) of the first lithium-nickel composite oxide to the weight (B) of the second lithium-nickel composite oxide. Specifically, the ratio (A / B) of the weight (A) of the first lithium-nickel composite oxide to the weight (B) of the second lithium-nickel composite oxide in the positive electrode active material may be 1 to 3.8, 1 to 3.6, 1 to 3.4, 1 to 3.2, 1 to 3, 1.2 to 3, 1.4 to 3, 1.6 to 3, or 1.8 to 3. By mixing the first lithium-nickel composite oxide and the second lithium-nickel composite oxide in the positive electrode active material at an appropriate weight ratio, the positive electrode active material can have improved high energy density and long life characteristics.

[0034] The first lithium-nickel-based composite oxide produced in a continuous reactor has a wide particle size distribution, and the second lithium-nickel-based composite oxide produced in a batch reactor has a narrow particle size distribution. By utilizing this, the inventors have developed a first lithium-nickel-based composite oxide, a second lithium-nickel-based composite oxide, and a cathode active material containing the same, which have improved high energy density and long life characteristics. 90 -D 10 / D 50 This defines the appropriate range for the span value calculated by

[0035] The first lithium nickel composite oxide span {(D 90 -D 10 ) / D 50} is 0.9 to 1.2, and may be, for example, 1 to 1.1.

[0036] The span of the second lithium nickel composite oxide is 0.9 to 1.2, and may be, for example, 1 to 1.1.

[0037] The span of the positive electrode active material is 1.5 to 2, and may be, for example, 1.55 to 1.95, 1.6 to 1.9, or 1.65 to 1.85.

[0038] First lithium nickel composite oxide The first lithium-nickel composite oxide may be in the form of secondary particles formed by agglomeration of a plurality of primary particles. The secondary particles may be spherical, ellipsoidal, polyhedral, or irregular in shape, and the primary particles may be spherical, ellipsoidal, plate-shaped, or a combination thereof.

[0039] The average particle size (D 50 ) may be 10 μm to 25 μm as described above, for example, 10 μm to 20 μm or 10 μm to 15 μm. Here, the average particle size of the first lithium-nickel-based composite oxide is determined by randomly selecting about 20 active materials in the form of secondary particles from an electron microscope photograph of the first lithium-nickel-based composite oxide, measuring the particle sizes, and determining the diameter of particles whose cumulative volume accounts for 50% by volume in the particle size distribution. 50 The average particle size (D 50 ) may refer to the average particle size of secondary particles.

[0040] The first lithium-nickel-based composite oxide may further include a coating layer located on the surface of the first lithium-nickel-based composite oxide (hereinafter, referred to as "core particle").

[0041] The coating layer can include, for example, Al, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, Ti, V, W, Y, Zn, Zr, or a combination thereof. As an example, the coating layer can include aluminum, cobalt, or a combination thereof. The coating layer can include, for example, aluminum oxide, lithium-aluminum oxide, or a combination thereof; or the coating layer can include cobalt oxide, lithium-cobalt oxide, or a combination thereof; or the coating layer can include aluminum-cobalt oxide, lithium-aluminum-cobalt oxide, or a combination thereof.

[0042] The coating layer may have a layered crystal structure, for example. When the first lithium nickel-based composite oxide and the coating layer both have a layered crystal structure, lithium intercalation and deintercalation can be further promoted.

[0043] When the coating layer contains aluminum, the aluminum content in the coating layer may be 0.05 mol% to 2 mol%, for example, 0.1 mol% to 1.5 mol%, 0.15 mol% to 1.3 mol%, or 0.2 mol% to 1.0 mol%, based on 100 mol% of the total metals (excluding lithium) in the first lithium-nickel-based composite oxide and the coating layer. This refers to the aluminum content in the coating layer, separate from the aluminum in the first lithium-nickel-based composite oxide, when the first lithium-nickel-based composite oxide contains aluminum. The aluminum content in the coating layer can be measured, for example, by SEM-EDS analysis of the surface or cross-section of the first lithium-nickel-based composite oxide. When the aluminum content in the coating layer satisfies this range, a uniform and thin coating layer can be formed.

[0044] When the coating layer contains cobalt, the cobalt content in the coating layer may be 0.01 mol% to 5 mol%, for example, 0.1 mol% to 4 mol%, 0.5 mol% to 3 mol%, or 1 mol% to 3 mol%, based on 100 mol% of the total metals, excluding lithium, in the first lithium-nickel composite oxide and the coating layer. This refers to the content of cobalt contained in the coating layer, separate from the cobalt in the first lithium-nickel composite oxide, when the first lithium-nickel composite oxide contains cobalt. The cobalt content in the coating layer can be measured, for example, by SEM-EDS analysis of the surface or cross-section of the first lithium-nickel composite oxide. When the cobalt content in the coating layer satisfies this range, a uniform and thin coating layer can be formed.

[0045] The coating layer may be in the form of a film that continuously surrounds the surface of the core particle, for example, 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 portion of the surface of the core particle is partially coated. The coating layer may be formed to completely surround the outermost surface of the first lithium-nickel-based composite oxide, and may be formed with a very thin and uniform thickness. As a result, the first lithium-nickel-based composite oxide has improved structural stability without increasing resistance or decreasing capacity, effectively suppresses side reactions with the electrolyte, reduces gas generation under high voltage and high temperature conditions, and achieves long-life characteristics.

[0046] The coating layer is characterized by its thin yet uniform thickness, ranging from several tens to several hundreds of nanometers. For example, the thickness deviation of the first coating layer within one positive electrode active material particle may be 20% or less, 18% or less, or 15% or less. Here, the coating layer thickness deviation refers to the coating layer thickness within one positive electrode active material particle. For example, the coating layer thickness deviation may be calculated by measuring the thickness at approximately 10 points in an electron microscope image of the cross section of one positive electrode active material particle, calculating the arithmetic average, and then dividing the absolute value of the difference between one data point and the arithmetic average value by the arithmetic average value and multiplying the result by 100. The fact that the coating layer thickness deviation or standard deviation satisfies the above range means that a coating layer of uniform thickness is well formed in the form of a film on the surface of the first lithium nickel-based composite oxide particle.

[0047] The coating layer may be a single layer structure containing both aluminum and cobalt, or a double layer structure including a first coating layer containing aluminum and a second coating layer containing cobalt.

[0048] For example, the coating layer may have a double layer structure including a first coating layer containing aluminum and a second coating layer containing cobalt, or may have a structure in which the first coating layer and the second coating layer are stacked in this order from the surface of the core particle. In this case, the second coating layer may further contain aluminum in addition to cobalt.

[0049] For example, the thickness of the first coating layer may be 10 nm to 150 nm, e.g., 15 nm to 125 nm, or 20 nm to 100 nm. The thickness of the second coating layer may be 250 nm or less, e.g., 70 nm to 250 nm, 80 nm to 240 nm, 90 nm to 220 nm, or 100 nm to 200 nm. The thicknesses of the first and second coating layers may be measured using, for example, SEM, TEM, TOF-SIMS, XPS, or EDS analysis, and the thickness range of the coating layers may be measured using a TEM-EDS line profile.

[0050] In this case, the first coating layer may be thinner than the second coating layer.

[0051] Meanwhile, during the coating layer formation process, aluminum and / or cobalt can diffuse into the core particles. Therefore, the first lithium-nickel-based composite oxide may further include a grain boundary coating region located on the surface of the primary particles inside the secondary particles, and the grain boundary coating region may include aluminum, cobalt, or a combination thereof. Here, the term "secondary particle" refers to the core particle, and the "interior of the secondary particle" may refer to the entire interior of the secondary particle excluding the surface, or may refer to the region extending from the center of the secondary particle toward the surface of the secondary particle, extending up to approximately 60% of the radius. The grain boundary coating region is a concept distinct from the coating layer on the surface of the core particle and refers to a coating region formed on the surface of the primary particles located inside the core particle. The presence of the grain boundary coating region can be confirmed by SEM-EDS analysis of the cross section of the first lithium-nickel-based composite oxide. According to one embodiment, the presence of the grain boundary coating region improves the structural stability of the lithium-nickel-based composite oxide, facilitating lithium ion mobility, thereby improving life and rate characteristics, and further improving high-temperature and high-voltage characteristics.

[0052] Secondary lithium nickel composite oxide The second lithium-nickel-based composite oxide may be in the form of a secondary particle formed by the aggregation of multiple primary particles, or in the form of a single particle. The secondary particle form is as described above for the first lithium-nickel-based composite oxide. Here, a single particle refers to a particle that exists independently without a grain boundary. It can refer to a single particle, a monolith structure, a single structure, or a non-aggregated particle, where particles morphologically exist as an independent phase without aggregation. For example, it can be a single crystal. The single particles may exist individually, or multiple single particles may physically contact each other to form an aggregate-like structure. For example, even if two to ten single particles are in contact with each other and loosely aggregated, each particle maintains a single crystal morphology without an internal grain boundary.

[0053] The average particle size of the second lithium nickel composite oxide (D 50 ) may be 2 μm to 9 μm as described above, and may be, for example, 2 μm to 8 μm, 2 μm to 7 μm, 2 μm to 6 μm, 2 μm to 5 μm, 2 μm to 4.5 μm, 2 μm to 4 μm, or 2.5 μm to 3.5 μm. Here, the average particle size of the second lithium-nickel-based composite oxide is determined by randomly selecting more than 20 single-particle active materials from an electron microscope photograph of the second lithium-nickel-based composite oxide, measuring the particle sizes, and determining the diameter of the particles whose cumulative volume accounts for 50% by volume in the particle size distribution. 50 The average particle size (D 50 ) is the average particle size (D 50 ) and in the case of single particle form, the average particle size of the single particle (D 50 ) can also refer to

[0054] The first lithium-nickel composite oxide and the second lithium-nickel composite oxide may each independently be a compound represented by the following chemical formula 1.

[0055] [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the above chemical formula 1, 0.9≦a1≦1.2, 0.8≦x1<1, 0 <y1≦0.2、0≦z1≦0.2、0.9≦x1+y1+z1≦1.1、および0≦b1≦0.1であり、M 1 and M 2 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, Y, and Zr, and X is one or more elements selected from F, P, and S. In Chemical Formula 1, M 1 and M 2 may be different elements.

[0056] In chemical formula 1, 0.85≦x1<1, 0 <y1≦0.15、および0≦z1≦0.15であるか、0.9≦x1<1、0<y1≦0.1、および0≦z1≦0.1であるか、0.9≦x1<1、0<y1≦0.08、および0≦z1≦0.05であるか、または0.95≦x1<1、0<y1≦0.05、および0≦z1≦0.05であってもよい。

[0057] As a specific example, the first lithium-nickel composite oxide and the second lithium-nickel composite oxide may be compounds represented by Chemical Formula 2 or Chemical Formula 3, respectively.

[0058] [Chemical formula 2] Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2 In the above chemical formula 2, 0.9≦a2≦1.2, 0.8≦x2<1, 0 <y2≦0.2、0≦z2≦0.2、0.9≦x2+y2+z2≦1.1、および0≦b2≦0.1であり、M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Zn, Y, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0059] In the formula 2, 0.85≦x2<1, 0 <y2≦0.15、および0≦z2≦0.15であるか、または0.9≦x2<1、0<y2≦0.1、および0≦z2≦0.1であるか、または0.9≦x2<1、0<y2≦0.08、および0≦z2≦0.05であるか、または0.95≦x2<1、0<y2≦0.05、および0≦z2≦0.05であってもよい。

[0060] [Chemical formula 3] Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3 In the above chemical formula 3, 0.9≦a3≦1.2, 0.8≦x3<1, 0 <y3≦0.2、0<z3≦0.2、0≦w3≦0.2、0.9≦x3+y3+z3+w3≦1.1、および0≦b3≦0.1であり、M 4 is one or more elements selected from the group consisting of Al and Mn, 5 is one or more elements selected from the group consisting of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, Zn, Y, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0061] In the formula 3, 0.85≦x3<1, 0 <y3≦0.15、0≦z3≦0.15、および0≦w3≦0.15であるか、0.9≦x3<1、0<y3≦0.1、0<z3≦0.1、および0≦w3≦0.1、0.9≦x3<1、0<y3≦0.08、0<z3≦0.05、および0≦w3≦0.1であるか、または0.95≦x3<1、0<y3≦0.05、0<z3≦0.05、および0≦w3≦0.05であってもよい。

[0062] The first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide may have a minimized cobalt content. For example, the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide may each independently have a cobalt content of 10 mol% or less, 9 mol% or less, 8 mol% or less, 7 mol% or less, 6 mol% or less, or 5 mol% or less, relative to 100 mol% of all metals excluding lithium. The lower limit is not specifically limited, but may be 0.1 mol% or more, 0.5 mol% or more, or 1 mol% or more. When the cobalt content of the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide satisfies the above range, the cobalt content can be minimized, thereby ensuring price competitiveness.

[0063] The first lithium-nickel composite oxide and the second lithium-nickel composite oxide may be the same or different from each other.

[0064] In one embodiment, the first lithium nickel-based composite oxide may be lithium nickel-cobalt-aluminum oxide, and the second lithium nickel-based composite oxide may be lithium nickel-cobalt-manganese oxide. For example, the first lithium nickel-based composite oxide may be lithium nickel-cobalt-aluminum oxide represented by Chemical Formula 4, and the second lithium nickel-based composite oxide may be lithium nickel-cobalt-manganese oxide represented by Chemical Formula 5. In this case, a positive electrode active material including these may maximize capacity characteristics, life characteristics, and energy density.

[0065] [Chemical formula 4] Li a4 Ni x4 Co y4 Al z4 M 6 w4 O 2-b4 X b4 In the above chemical formula 4, 0.9≦a4≦1.2, 0.8≦x4<1, 0 <y4≦0.2、0<z4≦0.2、0≦w4≦0.2、0.9≦x4+y4+z4+w4≦1.1、および0≦b4≦0.1であり、M 6 is one or more elements selected from the group consisting of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Zn, Y, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0066] [Chemical formula 5] Li a5 Ni x5 Co y5 Mn z5 M 7 w5 O 2-b5 X b5 In the above chemical formula 5, 0.9≦a5≦1.2, 0.8≦x5<1, 0 <y5≦0.2、0<z5≦0.2、0≦w5≦0.2、0.9≦x5+y5+z5+w5≦1.1、および0≦b5≦0.1であり、M 7 is one or more elements selected from the group consisting of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Al, Mo, Nb, Si, Sr, Ti, V, W, Zn, Y, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0067] positive electrode active material In one embodiment, the particle size distribution (D 10 , D 50 , D 90, span) can be satisfied within an appropriate range. At this time, the particle size distribution of the positive electrode active material is 10 , D 50 , D 90 , and span analysis" were calculated as described in the section.

[0068] D of the positive electrode active material 10 The thickness may be 2.2 μm to 3 μm, 2.2 μm to 2.9 μm, 2.2 μm to 2.8 μm, or 2.3 μm to 2.7 μm.

[0069] The average particle size (D 50 ) may be 7 μm to 10 μm, 7.5 μm to 9.5 μm, or 7.9 μm to 9.2 μm.

[0070] D of the positive electrode active material 90 The thickness may be 16 μm to 19 μm, 16.5 μm to 18.5 μm, or 16.9 μm to 18.2 μm.

[0071] In a particle size distribution graph f(x) of the positive electrode active material, where the x-axis represents particle size and the y-axis represents volume percent based on measurements using a particle size distribution analyzer using a laser diffraction method, the number of x-values ​​satisfying the following formula 1 may be two or less, one or less, or even just one. The particle size distribution graph can be obtained according to the method described in the "Particle Size Distribution" section of Evaluation Example 2. For example, the particle size distribution graph may be measured using a laser diffraction particle size analyzer such as the LS13320 (Beckman Coulter). Here, "the number of x-values ​​satisfying formula 1" refers to the number of x-coordinates at which f'(x) = 0 in the graph f'(x) obtained by differentiating the particle size distribution graph f(x), which corresponds to the number of peaks (maximum or minimum values) in the particle size distribution graph. [Formula 1] f'(x)=0

[0072] In the above formula 1, f(x) represents the particle size distribution graph of the positive electrode active material, and f′(x) represents the derivative of the particle size distribution graph.

[0073] This is because when a particle size distribution graph is obtained using a cathode active material in which a first lithium-nickel-based composite oxide as a counterpart produced in a continuous reactor and a second lithium-nickel-based composite oxide as small particles produced in a batch reactor are mixed in an appropriate weight ratio, there is one point where the differential value is 0, as shown in Example 1 of FIG. 11, and the number of x values ​​satisfying Equation 1 is two or less. On the other hand, when a particle size distribution graph is obtained using a cathode active material in which a first lithium-nickel-based composite oxide as a counterpart produced in a batch reactor and a second lithium-nickel-based composite oxide as small particles produced in a batch reactor are mixed, there are three points where the differential value is 0, as shown in Comparative Example 1 of FIG. 11, and it can be confirmed that the condition that the number of x values ​​satisfying Equation 1 is two or less is not met. This is because the first cathode active material as a counterpart produced in a continuous reactor has a relatively wide particle size distribution compared to the first lithium-nickel-based composite oxide as a counterpart produced in a batch reactor, and it is predicted that the particle size distribution of the cathode active material mixed with the second lithium-nickel-based composite oxide as small particles produced in a batch reactor will also be uniform.

[0074] The positive electrode active material may contain the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide in an amount of 90 wt % or more, 95 wt % or more, 99 wt % or more, 99.9 wt % or more, or 100 wt % relative to 100 wt % of the positive electrode active material.

[0075] In one embodiment, the positive electrode active material may include the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide in an amount of 100 wt % relative to 100 wt % of the positive electrode active material, i.e., the positive electrode active material may consist of the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide.

[0076] The pellet density of the positive electrode active material may be 3.4 g / cc to 3.8 g / cc, for example, 3.4 g / cc to 3.7 g / cc, 3.4 g / cc to 3.6 g / cc, or 3.4 g / cc to 3.5 g / cc. The pellet density of the positive electrode active material can be calculated by, for example, placing 3 g of each positive electrode active material into a mold having a diameter of 13 mm (1.3 cm) and pressing the mold at room temperature (25° C.) under a pressure of about 4 tons to produce powder pellets made only from the positive electrode active material, calculating the volume from the thickness of the powder pellet and the diameter of the mold, and dividing the weight by the volume.

[0077] Method for producing positive electrode active material The first lithium nickel-based composite oxide is prepared by mixing a precursor including, for example, a nickel hydroxide, a nickel oxide, or a combination thereof with a lithium source and heat-treating the mixture, and a continuous reactor may be used to prepare the precursor. The second lithium nickel-based composite oxide is prepared by mixing a precursor including, for example, a nickel hydroxide, a nickel oxide, or a combination thereof with a lithium source and heat-treating the mixture, and a batch reactor may be used to prepare the precursor. The precursor has a nickel content of 80 mol% or more relative to 100 mol% of the total metal.

[0078] After preparing the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide, they can be washed separately in washing water, and at this time, a coating material can be added. The coating material can include, for example, metal elements such as Al, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, Ti, V, W, Y, Zn, Zr, or a combination thereof. After washing or both washing and coating, the resulting mixture can be dried and then heat-treated. The coated first and second lithium-nickel-based composite oxides can be mixed to prepare a final cathode active material. During mixing, the ratio (A / B) of the weight of the first lithium-nickel-based composite oxide (A) to the weight of the second lithium-nickel-based composite oxide (B) satisfies a range of 1 to 4. The ratio (A / B) refers to the ratio of the weight of the first lithium-nickel-based composite oxide (A) to the weight of the second lithium-nickel-based composite oxide (B).

[0079] In one embodiment, a method for producing a positive electrode active material is provided, comprising: (i) mixing a first precursor containing a nickel-based hydroxide, a nickel-based oxide, or a combination thereof and a first lithium source in a continuous reactor and heat-treating the mixture to obtain a first lithium-nickel-based composite oxide in the form of large particles; (ii) mixing a second precursor containing a nickel-based hydroxide, a nickel-based oxide, or a combination thereof and a second lithium source in a batch reactor and heat-treating the mixture to obtain a second lithium-nickel-based composite oxide in the form of small particles; and (iii) mixing the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide so that the ratio (A / B) of the weight (A) of the first lithium-nickel-based composite oxide to the weight (B) of the second lithium-nickel-based composite oxide is 1 to 4.

[0080] In each of the first precursor and the second precursor, the nickel-based hydroxide or nickel-based oxide has a nickel content of 80 mol% or more relative to 100 mol% of the total metal. The lithium source may be lithium hydroxide, lithium carbonate, or a hydrate thereof.

[0081] The preparation method may further include a step of washing the obtained first lithium-nickel composite oxide with an aqueous solvent. Similarly, the preparation method may further include a step of washing the obtained second lithium-nickel composite oxide with an aqueous solvent. Alternatively, a coating step may be performed by adding a coating raw material in the washing step, followed by a drying and heat treatment step. For example, a first lithium-nickel composite oxide having a surface coated with Al and Co can be prepared by adding an Al raw material and the first lithium-nickel composite oxide to an aqueous solvent, mixing them, and then adding a Co raw material and mixing them. Similarly, a second lithium-nickel composite oxide having a surface coated with Al and Co can be prepared by adding an Al raw material and the second lithium-nickel composite oxide to an aqueous solvent, mixing them, and then adding a Co raw material and mixing them.

[0082] The first lithium-nickel composite oxide and the second lithium-nickel composite oxide may be mixed so that the ratio (A / B) of the weight (A) of the first lithium-nickel composite oxide to the weight (B) of the second lithium-nickel composite oxide is 1 to 3.8, 1 to 3.6, 1 to 3.4, 1 to 3.2, 1 to 3, 1.2 to 3, 1.4 to 3, 1.6 to 3, or 1.8 to 3, and in this case, the life characteristics can be improved while increasing the energy density.

[0083] positive electrode In another embodiment, a positive electrode is provided that includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector and including the above-described positive electrode active material.

[0084] According to one embodiment, the loading level of the positive electrode active material layer is 10 mg / cm 2 ~40mg / cm 2 may be, for example, 10 mg / cm 2 ~30mg / cm 2 or 10 mg / cm 2 ~20mg / cm 2 may be.

[0085] When applying a positive electrode active material according to an embodiment, it is advantageous to achieve such a loading level, and a positive electrode satisfying a loading level in this range is suitable for realizing a high-capacity, high-energy-density lithium secondary battery.

[0086] The content of the positive electrode active material may be 60 wt% to 99.9 wt%, 70 wt% to 99.8 wt%, 80 wt% to 99 wt%, 90 wt% to 99.8 wt%, or 94 wt% to 99 wt%, based on 100 wt% of the positive electrode active material layer.

[0087] The positive electrode active material layer may optionally further include a binder, a conductive material, or a combination thereof.

[0088] The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the positive electrode current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0089] The conductive material is used to impart conductivity to the electrode and can be any material that is electron-conductive and does not cause chemical changes in the battery. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0090] In the positive electrode active material layer, the content of the binder may be 0.1 wt % to 5 wt %, or 0.5 wt % to 3 wt %, relative to 100 wt % of the positive electrode active material layer, and the content of the conductive material may be 0.1 wt % to 5 wt %, or 0.5 wt % to 3 wt %, relative to 100 wt % of the positive electrode active material layer.

[0091] The positive electrode current collector may be, but is not limited to, aluminum foil.

[0092] Lithium secondary battery In yet another embodiment, there is provided a lithium secondary battery including the above-described positive electrode, negative electrode, and electrolyte. The lithium secondary battery may include a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte.

[0093] In another embodiment, there is provided an all-solid-state secondary battery comprising the positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode.

[0094] For convenience, the configuration of a lithium secondary battery using a liquid electrolyte will be described in detail below.

[0095] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 1 to 4 are schematic diagrams illustrating a lithium secondary battery according to an embodiment, with FIG. 1 illustrating a cylindrical type, FIG. 2 illustrating a prismatic type, and FIGS. 3 and 4 illustrating pouch types. Referring to FIGS. 1 to 4, a lithium secondary battery 100 may include an electrode assembly 40 having a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 housing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in FIG. 1. Also, as shown in FIG. 2, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the electrode assembly 40 to the outside.

[0096] Each of the components constituting the lithium secondary battery will be described below.

[0097] The positive electrode is the same as that described above, so a description thereof will be omitted, and the negative electrode, electrolyte, and separator will be described in order.

[0098] negative electrode The negative electrode for a lithium secondary battery includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and may optionally further include a binder, a conductive material, or a combination thereof.

[0099] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0100] Examples of substances that can reversibly intercalate / deintercalate lithium ions include carbonaceous negative electrode active materials.

[0101] The carbonaceous negative electrode active material can include 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. Soft carbon refers to a carbon material that can be graphitized and is a material that can be easily graphitized by heat treatment at a high temperature, for example, about 2800°C. Hard carbon is a carbon material that cannot be graphitized or is finely graphitized by heat treatment.

[0102] The negative electrode active material layer can further include other types of negative electrode active materials in addition to the carbonaceous negative electrode active material, and can further include, for example, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, and the like.

[0103] As the alloy of lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0104] As the material capable of doping and dedoping lithium, a Si-based negative electrode active material or a 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), a Si-Q alloy (where Q is 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), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0105] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and the surfaces of the silicon particles coated with amorphous carbon. For example, it may include secondary particles (cores) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surfaces 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 an amorphous carbon matrix.

[0106] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles and an amorphous carbon coating layer disposed on the core surface.

[0107] The Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0108] The negative electrode active material may be included in an amount of 90 wt % to 99.8 wt %, or 94 wt % to 99 wt %, based on 100 wt % of the negative electrode active material layer.

[0109] The binder serves to firmly adhere the negative active material particles to each other and to the negative active material to the negative current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0110] 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, and combinations thereof.

[0111] The aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0112] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0113] The dry binder may be a fiberizable polymeric material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0114] The conductive material is used to impart conductivity to the electrode and can be any material that is electron-conductive without causing chemical changes in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and carbon nanotubes; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0115] The content of the binder may be 0.1 wt % to 5 wt % based on 100 wt % of the negative electrode active material layer, and the content of the conductive material may be 0.1 wt % to 5 wt % based on 100 wt % of the negative electrode active material layer.

[0116] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the lithium secondary battery and has conductivity, and may be a copper foil having a thickness of 10 μm to 15 μm.

[0117] The negative electrode can be manufactured by a known method. For example, the negative electrode can be manufactured by mixing a negative electrode active material, and optionally a binder, a conductive material, or a combination thereof, in a solvent to prepare a negative electrode active material slurry, applying the negative electrode active material slurry to the negative electrode current collector, and then drying and rolling the slurry.

[0118] The solvent may be the same as the solvent contained in the positive electrode active material slurry, or may be an aqueous solvent.

[0119] electrolyte The electrolyte for a lithium secondary battery may be, for example, an electrolytic solution, which includes a non-aqueous organic solvent and a lithium salt.

[0120] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0121] The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0122] Examples of the carbonate solvent 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), butylene carbonate (BC), etc. Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0123] The non-aqueous organic solvents can be used alone or in combination of two or more.

[0124] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0125] The lithium salt is dissolved in an organic solvent and acts as a lithium ion source in the battery, enabling basic lithium secondary battery operation and promoting the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers of 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0126] 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 of these. Of course, 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.

[0127] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0128] The porous substrate may be a polymer membrane formed from any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON (registered trademark)), or a copolymer or mixture of two or more of these.

[0129] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0130] 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.

[0131] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a coating layer containing an organic material and a coating layer containing an inorganic material.

[0132] Examples and comparative examples of the present invention will be described below. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. [Example]

[0133] Examples and Comparative Examples Production Example 1: Large particles (A) produced in a continuous reactor A mixed solution is prepared by dissolving nickel sulfate, cobalt sulfate, and aluminum sulfate in distilled water as a solvent in a molar ratio of 95:3:2. A diluted ammonia water (NH4OH) solution and sodium hydroxide (NaOH) as a precipitant are prepared to form a complex compound. Then, the mixed metal raw material solution, diluted ammonia water (NH4OH) solution, and sodium hydroxide are each placed into a continuous reactor. The reaction is then carried out for approximately 7 days while stirring. After that, the slurry solution in the continuous reactor is filtered and washed with high-purity distilled water, and then dried for 24 hours to obtain the first nickel-based composite hydroxide (Ni 0.95 Co 0.03 Al 0.02 (OH)2) powder is obtained.

[0134] The first nickel-based composite hydroxide (Ni 0.95 Co 0.03 Al 0.02 (OH)2) and LiOH were mixed so that the molar ratio of lithium derived from LiOH to the total metal molar content of the obtained first nickel-based composite hydroxide was 1.03, and the mixture was heat-treated in an oxygen atmosphere at about 750°C for 10 hours to obtain the first lithium-nickel-based composite oxide (LiNi 0.95 Co 0.03 Al 0.02 O2) was obtained.

[0135] The obtained first lithium nickel composite oxide (LiNi 0.95 Co 0.03 Al 0.02 O2) is a secondary particle formed by the aggregation of multiple primary particles, and the average particle size of the secondary particles (D 50 ) is 12 μm.

[0136] After mixing aluminum sulfate with distilled water as a solvent, the prepared first lithium-nickel-based composite oxide was added and mixed for 20 to 60 minutes. The aluminum content in the aluminum sulfate was designed to be 0.5 mol% relative to 100 mol% of the total metals excluding lithium in the final first lithium-nickel-based composite oxide and the entire coating layer. Next, cobalt sulfate was added and mixed for 10 to 40 minutes. The cobalt content in the cobalt sulfate was designed to be 2.0 mol% relative to 100 mol% of the total metals excluding lithium in the final first lithium-nickel-based composite oxide and the entire coating layer. The solvent was removed from the mixed solution, which was then dried at 190°C and heat-treated at 690°C in an oxygen atmosphere for 8 hours to produce large particles (A) of the first lithium-nickel-based composite oxide.

[0137] Production Example 2: Large particles (B) produced in a batch reactor In Production Example 1, lithium nickel composite oxide (LiNi 0.95 Co 0.03 Al 0.02 O2) A first lithium nickel-based composite oxide having large particles (B) was prepared in substantially the same manner as in Preparation Example 1, except that a batch reactor was used instead of a continuous reactor during preparation.

[0138] Production Example 3: Small particles produced in a batch reactor A mixed solution is prepared by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in distilled water as a solvent in a molar ratio of 92:7:1. A diluted ammonia water (NH4OH) solution and sodium hydroxide (NaOH) as a precipitant are prepared to form the complex compound. Then, the mixed metal raw material solution, diluted ammonia water (NH4OH) solution, and sodium hydroxide are each placed into a batch reactor. The reaction is then carried out for approximately 20 hours while stirring. After that, the slurry solution in the batch reactor is filtered and washed with high-purity distilled water, and then dried for 24 hours to obtain a second nickel-based composite hydroxide (Ni 0.92 Co 0.07 Mn 0.01 (OH)2) powder is obtained.

[0139] In a batch reactor, the second nickel-based composite hydroxide and LiOH were mixed so that the molar ratio of lithium derived from LiOH to the total metal molar content of the obtained first nickel-based composite hydroxide was 1.04, and the mixture was heat-treated in an oxygen atmosphere at approximately 790°C for 10 hours to obtain small particles of the second lithium-nickel-based composite oxide (LiNi 0.92 Co 0.07 Mn 0.01 O2) was obtained.

[0140] The obtained second lithium nickel composite oxide (LiNi 0.92 Co 0.07 Mn 0.01 O2) is a secondary particle formed by the aggregation of multiple primary particles, and the average particle size of the secondary particles (D 50 ) is approximately 3 μm.

[0141] Example 1 (1) Manufacturing of positive electrode active material The large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were mixed in a weight ratio of 70:30 to prepare a positive electrode active material.

[0142] (2) Manufacturing of the positive electrode The prepared positive electrode active material, polyvinylidene fluoride as a binder, and carbon nanotubes as a conductive material were mixed in a weight ratio of 98.5:1:0.5 to prepare a composition for forming a positive electrode active material layer, which was then dispersed in N-methyl-2-pyrrolidone solvent to prepare a positive electrode slurry. The positive electrode was then coated on an aluminum foil current collector, dried, and rolled to prepare a positive electrode. At this time, the loading level of the positive electrode active material layer was 10 mg / cm. 2 and the density of the final rolled cathode is about 3.75 g / cc.

[0143] (3) Manufacture of lithium secondary batteries A half-cell was fabricated using the cathode, lithium metal counter electrode, and electrolyte in a conventional manner. A polytetrafluoroethylene separator was used, and the electrolyte was 1M LiPF6 dissolved in a solvent containing ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7. A lithium secondary battery was fabricated in a conventional manner.

[0144] Example 2 A positive electrode active material, a positive electrode, and a lithium secondary battery were prepared in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were mixed in a weight ratio of 75:25 when preparing the positive electrode active material.

[0145] Example 3 A positive electrode active material, a positive electrode, and a lithium secondary battery were prepared in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were mixed in a weight ratio of 65:35 when preparing the positive electrode active material.

[0146] Comparative Example 1 A positive electrode active material, a positive electrode, and a lithium secondary battery were prepared in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 were replaced by the large particles (B) of Preparation Example 2 mixed with the small particles of Preparation Example 3.

[0147] Comparative Example 2 A positive electrode active material, a positive electrode, and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were not mixed and only the large particles (B) of Preparation Example 2 were used.

[0148] Comparative Example 3 A positive electrode active material, a positive electrode, and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were not mixed and only the small particles of Preparation Example 3 were used.

[0149] Comparative Example 4 A positive electrode active material, a positive electrode, and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 were not mixed with the small particles of Preparation Example 3, and only the large particles (A) of Preparation Example 1 were used.

[0150] Comparative Example 5 A positive electrode active material, a positive electrode, and a lithium secondary battery were prepared in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were mixed in a weight ratio of 40:60 when preparing the positive electrode active material.

[0151] Comparative Example 7 A positive electrode active material, a positive electrode, and a lithium secondary battery were prepared in substantially the same manner as in Example 1, except that the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 were mixed in a weight ratio of 20:80 when preparing the positive electrode active material.

[0152] Evaluation example 1. SEM and SEM-EDS analysis Fig. 6 is an SEM photograph of the surface of the first lithium-nickel composite oxide, which is the large particles (A) produced in Production Example 1. Fig. 9 is an SEM photograph of the surface of the first lithium-nickel composite oxide, which is the large particles (B) produced in Production Example 2. Fig. 10 is an SEM photograph of the surface of the second lithium-nickel composite oxide, which is the small particles produced in Production Example 3.

[0153] Comparing Figure 6 of Preparation Example 1 with Figure 9 of Preparation Example 2, it can be seen that the particle size distribution of the first lithium nickel-based composite oxide, which is the large particles (A) of Preparation Example 1 prepared in a continuous reactor, was relatively broad, and that the particles of the first lithium nickel-based composite oxide, which is the large particles (B) of Preparation Example 2 prepared in a batch reactor, were more uniform.

[0154] In addition, the first lithium-nickel-based composite oxide particles, which are large particles (A) produced in Production Example 1, were cut using a focused ion beam (FIB) and the cross section was subjected to SEM-EDS analysis. Figure 7 is an image in which the aluminum element is highlighted in the SEM-EDS analysis of the fracture surface of the first lithium-nickel-based composite oxide, which are large particles (A) in Production Example 1. Figure 8 is an image in which the cobalt element is highlighted in the SEM-EDS analysis of the fracture surface of the first lithium-nickel-based composite oxide, which are large particles (A) in Production Example 1.

[0155] 7 and 8, it can be seen that aluminum and cobalt coatings were uniformly formed on the surfaces of the secondary particles of the first lithium nickel-based composite oxide and on the interfaces between the primary particles.

[0156] Evaluation example 2: Particle size analysis (1) Particle size distribution graph The particle size distribution graph of the lithium nickel composite oxides prepared in Preparation Examples 1 to 3 and the positive electrode active materials prepared in Example 1 and Comparative Example 1 is shown in FIG.

[0157] The particle size distribution graph was analyzed using a laser particle size analyzer LS133320 (Beckmann Coulter) under the following analysis conditions.

[0158] -Analysis conditions: pump speed (55%), sample ultrasonic dispersion 40KHz ultrasonic (60s), run length 60s, refractive index sample RI 1.6, e-factor 1.00, sample amount 0.20g, sample dispersant: 10% sodium hexamethaphosphate 1ml

[0159] As can be seen from FIG. 11, the particle size of the first lithium-nickel-based composite oxide (A), which is large particles (A) produced in a continuous reactor, is more uniformly and widely distributed than the particle size of the first lithium-nickel-based composite oxide (B), which is large particles (B) produced in a batch reactor. Thus, the particle size of the cathode active material of Example 1, which is a mixture of large particles (A) produced in a continuous reactor and small particles produced in a batch reactor, is more uniformly distributed than the particle size of the cathode active material of Comparative Example 1, which is a mixture of large particles (B) produced in a batch reactor and small particles produced in a batch reactor.

[0160] Furthermore, in the particle size distribution graph, it was confirmed that in Example 1, the number of points at which the differential value was 0 was 1, and the condition that the number of x values ​​that satisfied the following formula 1 was 2 or less was met. On the other hand, in Comparative Example 1, the number of points at which the differential value was 0 was 3, and the condition that the number of x values ​​that satisfied the following formula 1 was 2 or less was not met. [Formula 1] f'(x)=0

[0161] In the above formula 1, f(x) represents the particle size distribution graph of the positive electrode active material, and f′(x) represents the derivative of the particle size distribution graph.

[0162] (2)D 10 , D 50 , D 90 , and span analysis The particle size distribution characteristics of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were analyzed using PSA (Particle Size Analysis), and the results are shown in Table 1. In Table 1, the spans are rounded to two decimal places and are displayed to two decimal places.

[0163] In Table 1 below, the span is (D 90 -D 10 ) / D 50 means.

[0164] [Table 1]

[0165] Referring to Table 1, it was confirmed that the span of the positive electrode active materials of Examples 1 to 3, which were prepared by mixing the large particles (A) of Production Example 1 produced in a continuous stirred tank reactor with the small particles of Production Example 3, and in which the weight ratio of the large particles (A) to the small particles was approximately 1:4, was in the range of 1.5 to 2.

[0166] On the other hand, in Comparative Example 1, in which the large particles (B) of Production Example 2 produced in a batch reactor were mixed with the small particles of Production Example 3, it was confirmed that the span was smaller than those of Examples 1 to 3. Furthermore, unlike Examples 1 to 3, the large particles (A) of Production Example 1, which were produced in a continuous stirred tank reactor, were mixed with the small particles of Production Example 3. However, in Comparative Examples 5 and 6, in which the weight ratio of the large particles (A) to the small particles did not generally satisfy the range of 1:4, it was confirmed that the span range of 1.5 to 2 was not satisfied.

[0167] Furthermore, Comparative Example 4, which contained only the large particles (A) of Production Example 1 produced in a continuous stirred tank reactor, and Comparative Example 3, which contained only the small particles of Production Example 3, had spans of 1.05 and 1.03, respectively, which were confirmed to be within the range of 0.9 to 1.2. On the other hand, Comparative Example 2 containing only the large particles (B) of Production Example 2 produced in a batch reactor had a span of 0.29, which was confirmed not to satisfy the range of 0.9 to 1.2. This confirmed that when large particles (A) and small particles produced in a continuous stirred tank reactor are mixed and the weight ratio of large particles (A) to small particles is within the range of approximately 1:4, the span satisfies the range of 0.9 to 1.2.

[0168] Evaluation example 3: Pellet density measurement 3 g of each of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 6 was placed in a mold with a diameter of 13 mm (1.3 cm) and pressed at room temperature (25°C) under a pressure of approximately 4 tons to prepare powder pellets made solely from the positive electrode active material. The volume of the prepared powder pellets was calculated from the thickness and mold diameter, and the pellet density was calculated by dividing the weight by the volume. The results are shown in Table 2 below.

[0169] [Table 2]

[0170] Referring to Table 2, it was confirmed that the positive electrode active materials of Examples 1 to 3, which were prepared by mixing the large particles (A) of Production Example 1 produced in a continuous stirred tank reactor with the small particles of Production Example 3, and in which the weight ratio of the large particles (A) to the small particles was within the range of approximately 1:4, had superior pellet density compared to Comparative Examples 1 to 6, which contained lithium-nickel composite oxides with the same or similar nickel content.

[0171] Comparative Example 1, in which the large particles (B) of Production Example 2 produced in a batch reactor were mixed with the small particles of Production Example 3, and Comparative Examples 5 and 6, in which the large particles (A) of Production Example 1 produced in a continuous stirred tank reactor were mixed with the small particles of Production Example 3 but the weight ratio of the large particles (A) to the small particles did not generally satisfy the range of 1:4, showed better pellet density than Comparative Examples 2 to 4, in which large particles (B), small particles, or large particles (A) were used alone.

[0172] This confirmed that when large particles (A) and small particles produced in a continuous stirred tank reactor are mixed and the weight ratio of large particles (A) to small particles is within the range of approximately 1:4, an excellent pellet density can be obtained.

[0173] Evaluation example 4: Performance evaluation (1) Single charge / discharge capacity (0.2C) and initial charge / discharge efficiency The lithium secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were charged at a constant current of 0.2 C at 25°C to an SOC of 90%, aged for 48 hours, and then cut off at a current rate of 0.05 C while maintaining 4.3 V in a constant current / constant voltage mode. Subsequently, they were discharged at a constant current rate of 0.2 C until the voltage reached 3.0 V (formation step).

[0174] The initial charge-discharge efficiency was evaluated using the following formula 1, and the evaluation results are shown in Table 3. In Table 3 below, the initial charge-discharge efficiency was rounded to the second decimal place and is shown to the first decimal place. [Formula 1] Initial charge / discharge efficiency (%) = (1 time discharge capacity (0.2C) / 1 time charge capacity (0.2C)) × 100

[0175] (2) Energy density The energy density of the lithium secondary batteries manufactured in Examples 1 to 3 and Comparative Examples 1 to 6 was calculated by multiplying the pellet density measured in Evaluation Example 2 by the single discharge capacity (0.2 C), and the results are shown in Table 3 below.

[0176] (3) High temperature life The lithium secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were charged at a constant current of 1.0 C at 45°C to an SOC of 90%, and then aged for 48 hours. After that, they were cut off at a current rate of 0.05 C while maintaining 4.4 V in a constant current / constant voltage mode. Then, they were discharged at a constant current rate of 1.0 C until the voltage reached 3.0 V (formation stage, 1 st cycle).

[0177] 1 of the chemical conversion steps st The cycled lithium secondary batteries were charged at a constant current of 1.0 C at 45°C until the voltage reached 4.4 V. After the charging was completed, the cells were rested for approximately 10 minutes, and then discharged at a constant current of 1.0 C until the voltage reached 3 V. This cycle was repeated 50 times in total and evaluated.

[0178] The high temperature life was evaluated by the following formula 2, and the results are shown in the following Table 3. In the following Table 3, the energy density was rounded off to two decimal places and shown to one decimal place. [Formula 2] High temperature life (%) = (50 cycle discharge capacity / 1 cycle discharge capacity) x 100

[0179] [Table 3]

[0180] Referring to Table 3 above, it can be seen that Examples 1 to 3, which use a cathode active material in which the large particles (A) of Preparation Example 1 prepared in a continuous reactor and the small particles of Preparation Example 3 are mixed in an appropriate ratio, can achieve a higher energy density and have excellent high-temperature life characteristics compared to Comparative Examples 1 to 6, which contain lithium-nickel-based composite oxides with the same nickel content.

[0181] Specifically, Comparative Examples 2 and 3 used only the large particles (B) of Preparation Example 2 or only the small particles of Preparation Example 3, both prepared in a batch reactor, as the cathode active material, and were found to have inferior energy density and high-temperature life characteristics compared to Comparative Example 1, which used a mixture of these. However, Comparative Example 1, which mixed the large particles (B) of Preparation Example 2 and the small particles of Preparation Example 3 prepared in a batch reactor in the same weight ratio as Example 1, was found to have inferior single charge / discharge capacity, initial charge / discharge efficiency, energy density, and high-temperature life compared to Example 1, which used the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 prepared in a continuous reactor.

[0182] This confirms that the mixture of large particles produced in a continuous reactor with small particles is superior to the large particles produced in a batch reactor in single charge / discharge capacity, initial charge / discharge efficiency, energy density, and high-temperature life characteristics.

[0183] Meanwhile, Comparative Examples 4 to 6 used only the large particles (A) of Preparation Example 1 produced in a continuous reactor or a mixture of the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3 as the positive electrode active material. It was confirmed that, compared to Comparative Example 4, which used only the large particles (A) of Preparation Example 1, Comparative Examples 5 and 6, which used a mixture of the large particles (A) of Preparation Example 1 and the small particles of Preparation Example 3, achieved relatively excellent energy density and high-temperature cycle life characteristics. However, Comparative Examples 5 and 6 showed inferior results in single charge / discharge capacity, initial charge / discharge efficiency, energy density, and high-temperature cycle life characteristics compared to Examples 1 to 3. This confirmed that mixing large particles and small particles produced in a continuous reactor so that the weight ratio of large particles to small particles was approximately 1:4 resulted in excellent single charge / discharge capacity, excellent initial charge / discharge efficiency, high energy density, and excellent high-temperature cycle life characteristics.

[0184] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited to these, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the claims also fall within the scope of the present invention. [Explanation of symbols]

[0185] 100: Lithium secondary battery 10: Positive electrode 11: Positive lead tap 12: Positive terminal 20: Negative electrode 21: Negative lead tap 22: Negative terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing material 70: Electrode tap 71: Positive tap 72: Negative tap

Claims

1. A bimodal type positive electrode active material including a first lithium-nickel-based composite oxide that is a large particle and a second lithium-nickel-based composite oxide that is a small particle, In each of the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide, the nickel content is 80 mol % or more relative to 100 mol % of all metals excluding lithium, a ratio (A / B) of a weight of the first lithium-nickel composite oxide (A) to a weight of the second lithium-nickel composite oxide (B) in the positive electrode active material is 1 to 4; The first lithium nickel composite oxide span {(D ９０ -D １０ ) / D ５０ } is 0.9 to 1.2, The second lithium nickel-based composite oxide has a span of 0.9 to 1.2, The span of the positive electrode active material is 1.5 to 2. Positive electrode active material for lithium secondary batteries.

2. The average particle size (D ５０ 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the particle size is 10 μm to 25 μm.

3. The average particle size (D ５０ 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the particle size is 2 μm to 9 μm.

4. D of the positive electrode active material １０ 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the particle size is 2.2 μm to 3 μm.

5. The average particle size (D ５０ 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the particle size is 7 μm to 10 μm.

6. D of the positive electrode active material ９０ The positive electrode active material for a lithium secondary battery according to claim 1, wherein the particle size is 16 μm to 19 μm.

7. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein, based on the results of measurement using a laser diffraction particle size analyzer such as LS13320 (Beckman Coulter), in a particle size distribution graph f(x) where the x-axis represents particle size and the y-axis represents volume percent, the number of x values ​​satisfying the following formula 1 is 2 or less: [Formula 1] f'(x)=0 In the above formula 1, f(x) represents the particle size distribution graph of the positive electrode active material, and f′(x) represents the derivative of the particle size distribution graph.

8. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the first lithium-nickel-based composite oxide and the second lithium-nickel-based composite oxide are the same or different and are each independently represented by the following Chemical Formula 1: [Chemical formula 1] Li ａ１ Ni ｘ１ M １ ｙ１ M ２ ｚ１ O ２－ｂ１ X ｂ１ In the above chemical formula 1, 0.9≦a1≦1.2, 0.8≦x1<1, 0<y1≦0.2, 0≦z1≦0.2, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1; M １ and M ２ are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, Y, and Zr, and X is one or more elements selected from F, P, and S.

9. the first lithium nickel-based composite oxide is lithium nickel-cobalt-aluminum oxide, 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the second lithium nickel composite oxide is a lithium nickel-cobalt-manganese oxide.

10. The positive electrode active material for a lithium secondary battery according to claim 1 , further comprising a coating layer located on a surface of the first lithium-nickel-based composite oxide and / or the second lithium-nickel-based composite oxide.

11. 11. The positive electrode active material for a lithium secondary battery according to claim 10, wherein the coating layer comprises Al, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, Ti, V, W, Y, Zn, Zr, or a combination thereof.

12. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the pellet density of the positive electrode active material measured by placing the material in a mold having a diameter of 13φ (1.3 cm) and pressing the mold at room temperature (25°C) under a pressure of about 4 tons is 3.4 g / cc to 3.8 g / cc.

13. a positive electrode current collector, and A positive electrode active material layer located on the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to any one of claims 1 to 12 A positive electrode for a lithium secondary battery comprising:

14. The loading level of the positive electrode active material layer is 10 mg / cm ２ ~40 mg / cm ２ The positive electrode for a lithium secondary battery according to claim 13,

15. The positive electrode for a lithium secondary battery according to claim 13 , wherein the positive electrode active material layer further comprises a binder, a conductive material, or a combination thereof.

16. A lithium secondary battery comprising the positive electrode of claim 13, a negative electrode, and an electrolyte.

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