Positive electrode active material, positive electrode, and lithium secondary battery

Abstract

The present invention relates to a positive electrode active material, and more particularly to a positive electrode and lithium secondary battery containing the same, which can simultaneously solve the problems of conventional secondary particles and single particles. The positive electrode active material contains particles such as conventional single particles as primary particles and secondary particles formed by the aggregation of multiple primary particles, thereby improving cell characteristics such as the lifespan of lithium secondary batteries and the amount of gas generated, as well as having excellent density characteristics and improving energy density.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2023-0056231 dated April 28, 2023, and Korean Patent Application No. 10-2024-0057193 dated April 29, 2024, and all content disclosed in the documents of said Korean patent applications is incorporated herein by reference.

[0002] This invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0003] Recently, the demand for high-capacity secondary batteries has increased due to advancements in technologies such as electric vehicles, and consequently, research on high-nickel (High Ni) cathode active materials with superior capacity characteristics is being actively conducted.

[0004] High-nickel positive electrode active materials, formed in a secondary particle structure where primary particles aggregate, undergo structural degeneration during charging and discharging of lithium-ion batteries. However, this also results in relative changes in the lattice structure constant, i.e., significant volume changes within the unit cell. Such volume changes can cause cracks within the positive electrode active material. Furthermore, cracks can also occur in the positive electrode active material due to pressure during electrode rolling.

[0005] The cracks that occur in the high-nickel positive electrode active material in this way worsen during the charging and discharging process of the lithium secondary battery. This can prevent the electrolyte from reaching the cracks, or cause them to act as voids that reduce conductivity, thereby reducing the lifespan characteristics of the lithium secondary battery or contributing to increased resistance.

[0006] To minimize crack formation in such secondary particle structures, attempts have been made to manufacture cathode active materials in single-particle form. However, such single-particle cathode active materials have a problem in that the particle size is non-uniform, and the particle size distribution of the single-particle cathode active material obtained after grinding becomes large. In addition, single-particle cathode active materials have a small specific surface area and weak cell resistance characteristics.

[0007] Therefore, there is a need to develop cathode active materials that can simultaneously solve the problems of both secondary particles and single particles.

[0008] On the other hand, Korean Patent Publication No. 10-1785262 (Patent Document 1) discloses large-sized secondary particles that include aggregated primary particles, the secondary particles contain nickel-based lithium transition metal oxides, the average particle size of the primary particles is 3 to 5 μm, and the average particle size of the secondary particles is 10 to 20 μm. Such large-sized secondary particles can improve rolling density and minimize cracks caused by rolling by including primary particles with an average particle size at the micron level, and can improve cell properties by improving the specific surface area due to the structure of the secondary particles.

[0009] To manufacture a positive electrode active material in the form of secondary particles, where the size of the primary particles is at the micron level, it is necessary to perform heat treatment at a higher temperature than for secondary particles, where the size of the primary particles is at the submicron level (less than 1 μm), as disclosed in Patent Document 1. However, the higher the heat treatment temperature, the more the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure, causing a decrease in crystallinity, which in turn degrades the performance of the positive electrode active material. In particular, nickel is the weakest element in the degeneration of the layered structure of the lithium transition metal composite oxide into a rock salt structure at high heat treatment temperatures, so the degeneration becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the positive electrode active material is high. Therefore, conventionally, as a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level, it has only been possible to apply it to mid-nickel (Mid Ni) positive electrode active materials in which the nickel content among the transition metals of the lithium transition metal composite oxide is at the 50 mol level, as described in Patent Document 1. However, it has been impossible to manufacture a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level for high-nickel (High Ni) positive electrode active materials, which have a high nickel content among the transition metals of the lithium transition metal composite oxide and excellent capacitance characteristics. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] KR10-1785262 B1 [Patent Document 2] KR10-2017-0119573 A [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The problem that this invention aims to solve is to provide a positive electrode active material that can simultaneously solve the problems of both secondary particles and single particles in conventional high-nickel (High Ni) positive electrode active materials.

[0012] In other words, the present invention was derived to solve the problems of the above-mentioned conventional technology, and aims to provide a positive electrode active material that has excellent density characteristics and can improve energy density, as well as cell characteristics such as improved lifespan and reduced gas generation, by realizing a positive electrode active material in the form of secondary particles with primary particle size at the micron level, as a high-nickel (High Ni) positive electrode active material in which the nickel content among the transition metals of lithium transition metal composite oxide is high and has excellent capacity characteristics.

[0013] Furthermore, the present invention aims to provide a positive electrode and a lithium secondary battery containing the above-mentioned positive electrode active material. [Means for solving the problem]

[0014] To solve the above problems, the present invention provides a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery.

[0015] (1) The present invention includes secondary particles formed by the aggregation of multiple primary particles, wherein the average particle size of the multiple primary particles measured from SEM images is 1.5 μm or more and 5.0 μm or less, the particle size of the primary particles is the particle size based on the major axis of the primary particles, and when the volume value is calculated from the following formula 5 for each primary particle observed from the SEM image (measurement magnification 3,000x) of the surface of the secondary particles, the degree of single particle formation (Dv) corresponds to the diameter of the volume at the point where the cumulative volume distribution of the primary particles reaches 50%. 50 The present invention provides a positive electrode active material having a diameter of 1.2 μm or more and 3.8 μm or less.

number

[0016] (2) In the present invention, in (1) above, the degree of single particle formation (Dv 50To provide a positive electrode active material in which [[ID=]] is 1.65 μm or more and 3.55 μm or less.

[0017] (3) The present invention provides a positive electrode active material containing a lithium transition metal composite oxide containing nickel, cobalt, and manganese in the above (1) or (2).

[0018] (4) The present invention provides a positive electrode active material containing a lithium transition metal composite oxide containing 60 mol% or more of nickel among the total transition metals in any one of the above (1) to (3).

[0019] (5) The present invention provides a positive electrode active material containing a lithium transition metal composite oxide having an average composition represented by the following chemical formula 1 in any one of the above (1) to (4). [Chemical formula 1] Li x Ni a Co b Mn c M 1 d O2 In the chemical formula 1, M 1 is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, S, and Y, and 0.9 ≤ x ≤ 1.3, 0.6 ≤ a < 1.0, 0 < b < 0.4, 0 < c < 0.4, 0 ≤ d ≤ 0.2, and a + b + c + d = 1.

[0020] (6) The present invention provides a positive electrode active material in which the plurality of primary particles include single crystal primary particles in any one of the above (1) to (5).

[0021] (7) The present invention provides a positive electrode active material in which the secondary particles have an average particle diameter (D 50 ) of 7.0 μm or more and 20.0 μm or less according to the volume cumulative distribution measured using a laser diffraction particle size analyzer in any one of the above (1) to (6).

[0022] (8) The present invention provides a positive electrode containing the positive electrode active material according to any one of the above (1) to (7).

[0023] (9) The present invention provides a lithium secondary battery comprising a positive electrode according to (8) above, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. [Effects of the Invention]

[0024] The positive electrode active material of the present invention is a high-nickel (High Ni) positive electrode active material that can simultaneously solve the problems of both secondary particles and single particles in conventional materials. By realizing a positive electrode active material in the form of secondary particles with a primary particle size at the micron level, it is possible to improve cell characteristics such as the lifespan of lithium secondary batteries and the amount of gas generated, as well as improve density characteristics and energy density. [Brief explanation of the drawing]

[0025] [Figure 1] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 1. [Figure 2] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 2. [Figure 3] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 3. [Figure 4] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 4. [Figure 5] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 5. [Figure 6] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 6. [Figure 7] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 7. [Figure 8] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 8. [Figure 9](A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 9. [Figure 10] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 10. [Figure 11] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 11. [Figure 12] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Comparative Example 1. [Figure 13] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Comparative Example 2. [Figure 14] (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Comparative Example 3. [Figure 15] Comparative Example 4 shows (A) an SEM image of the positive electrode active material and (B) an SEM image of a cross-section of the positive electrode active material. [Figure 16] This is an SEM image of the positive electrode active material (A) in Comparative Example 6. [Figure 17] This is a segmentation image showing multiple lithium composite transition metal oxides segmented by performing image analysis based on an artificial intelligence model on the SEM image of the positive electrode active material of Example 1. [Figure 18] This is a segmentation image showing multiple lithium composite transition metal oxides segmented by performing image analysis based on an artificial intelligence model on the SEM image of the positive electrode active material of Comparative Example 1. [Figure 19] This is a TEM image of the cross-section of the positive electrode active material in Example 1. [Figure 20] This is a TEM image of the cross-section of the positive electrode active material in Example 2. [Figure 21] This is a TEM image of the cross-section of the positive electrode active material in Example 8. [Figure 22] This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 1. [Figure 23] This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 2. [Figure 24]This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 3. [Figure 25] This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 4. [Figure 26] This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 8. [Figure 27] This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 10. [Figure 28] This is an EBSD pattern image of the cross-section of the positive electrode active material in Example 11. [Figure 29] This is an EBSD pattern image of the cross-section of the positive electrode active material of Comparative Example 3. [Figure 30] This is an EPMA analysis image of the positive electrode active material of Example 1. [Figure 31] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 1, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 32] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 2, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 33] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 3, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 34] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 4, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 35]This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 5, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 36] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 6, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 37] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 7, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 38] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 8, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 39] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 9, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 40] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 10, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 41]This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 11, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 42] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Comparative Example 1, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 43] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Comparative Example 3, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a linear scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 44] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 1, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 45] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 2, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 46] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 3, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, which increases from left to right, on a log scale, and the y-axis represents the weight distribution, which increases from bottom to top. [Figure 47] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 4, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 48] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 5, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, which increases from left to right, on a log scale, and the y-axis represents the weight distribution, which increases from bottom to top. [Figure 49] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 6, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 50] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 7, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 51] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 8, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 52] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 9, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 53] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 10, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 54]This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Example 11, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 55] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Comparative Example 1, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, with the x-value increasing from left to right on a log scale, and the y-axis represents the weight distribution, with the y-value increasing from bottom to top. [Figure 56] This frequency distribution graph shows the cumulative volume distribution of the positive electrode active material of Comparative Example 3, measured using a laser diffraction particle size analyzer. The x-axis represents the particle diameter, which increases from left to right, on a log scale, and the y-axis represents the weight distribution, which increases from bottom to top. [Modes for carrying out the invention]

[0026] The present invention will be described in more detail below to facilitate understanding of it.

[0027] The terms and words used in the description and claims of this invention should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​this invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0028] In this invention, the term "primary particle" refers to the smallest particle unit that can be distinguished as a single mass when a cross-section of the positive electrode active material is observed using a scanning electron microscope (SEM), and can consist of a single crystal or multiple crystal grains.

[0029] In this invention, the term "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles. The average particle size of the secondary particle can be measured using a particle size analyzer.

[0030] In this invention, the term "average particle size (D)" is used. 50 )" refers to the particle size at the 50% point of the cumulative volume distribution by particle size. The average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (for example, Microtrac's S3500), measuring the difference in diffraction patterns due to particle size as the particles pass through the laser beam to calculate the particle size distribution, and then calculating the particle diameter at the point where the cumulative volume distribution by particle size in the measuring device reaches 50%. 50 It can be measured.

[0031] In this invention, the term "major axis of primary particle" refers to the length of the longest line segment obtained when a line is drawn passing through two points at the boundary of a primary particle, as observed from an SEM image of the surface or cross-section of a secondary particle.

[0032] In this invention, the term "minor axis of primary particle" refers to the length of the shortest line segment obtained when a line is drawn passing through two points at the boundary of a primary particle, as observed from an SEM image of the surface or cross-section of a secondary particle.

[0033] positive electrode active material The present invention provides a positive electrode active material.

[0034] According to one embodiment of the present invention, the material includes secondary particles formed by the aggregation of a plurality of primary particles, and the plurality of primary particles may have an average particle size of 1.5 μm or more and 5.0 μm or less, as measured from an SEM image.

[0035] According to one embodiment of the present invention, the secondary particle is a secondary particle formed by the aggregation of a plurality of primary particles, and may consist of at least two, and more specifically, at least three or more primary particles.

[0036] According to one embodiment of the present invention, the plurality of primary particles may have an average particle size measured from an SEM image of 1.5 μm or more, 1.6 μm or more, 1.7 μm or more, 1.8 μm or more, 1.9 μm or more, 2.0 μm or more, 2.1 μm or more, 2.2 μm or more, 2.3 μm or more, 2.4 μm or more, or 2.5 μm or more, and may also be 5.0 μm or less, 4.9 μm or less. The particle size may be 4.8 μm or less, 4.7 μm or less, 4.6 μm or less, 4.5 μm or less, 4.4 μm or less, 4.3 μm or less, 4.2 μm or less, 4.1 μm or less, 4.0 μm or less, 3.9 μm or less, 3.8 μm or less, 3.7 μm or less, 3.6 μm or less, 3.5 μm or less, 3.4 μm or less, 3.3 μm or less, 3.2 μm or less, 3.1 μm or less, or 3.0 μm or less. Here, when measuring the average particle size for the plurality of primary particles from the SEM image, the particle size of each primary particle may be the particle size based on the major axis of the primary particle. Within this range, the rolling density of the positive electrode active material can be further improved, and the lifespan of the lithium secondary battery can be further improved.

[0037] According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide containing nickel, cobalt, and manganese. Specifically, the positive electrode active material may include a lithium transition metal composite oxide containing 60 mol% or more nickel of the total transition metal. The lithium transition metal composite oxide may consist of primary particles, secondary particles, and the positive electrode active material itself containing these. Specifically, the positive electrode active material may include secondary particles formed by the aggregation of a plurality of primary particles made of the lithium transition metal composite oxide.

[0038] According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide having an average composition represented by the following chemical formula 1.

[0039] [Chemical formula 1] Li x Ni a Co b Mn c M 1 d O2

[0040] In the above chemical formula 1, M 1 x is one or more elements selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, S, and Y, and 0.9≦x≦1.3, 0.6≦a<1.0, 0 <b<0.4、0<c<0.4、0≦d≦0.2、a+b+c+d=1である。

[0041] According to one embodiment of the present invention, in the chemical formula 1, x is the molar ratio of lithium to the transition metal in the lithium transition metal composite oxide, and may be 0.9 or more, 0.95 or more, or 1.0 or more, or it may be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0042] According to one embodiment of the present invention, in the chemical formula 1, a, b, c, and d are, respectively, transition metals, nickel (Ni), cobalt (Co), manganese (Mn), and doping element (M 1 ) may be the mole fraction of ). For example, a is the mole fraction of nickel (Ni) among the transition metals, and may be 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, 0.88 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, or 0.96 or more, and may also be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. Also, b is the mole fraction of cobalt (Co) among the transition metals, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. c is the mole fraction of manganese (Mn) among the transition metals, and may be greater than 0, 0.01 or more, or 0.05 or more, and may also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. d is the doping element (Mn) among the transition metals. 1This is the mole fraction of 0, and may be 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, or 0.19 or more. Furthermore, the values ​​may be less than 0.20, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. By adjusting the composition of the lithium transition metal composite oxide as described above, the capacity can be further improved.

[0043] According to one embodiment of the present invention, the plurality of primary particles may include single-crystal primary particles, in which case the rolling density of the positive electrode active material can be further improved. The single-crystal primary particles refer to primary particles made of a single crystal.

[0044] According to one embodiment of the present invention, the secondary particles have an average particle size (D) determined by the volume cumulative distribution measured using a laser diffraction particle size analyzer. 50 The particle size may be 7.0 μm or more and 20.0 μm or less. For example, the secondary particle may have an average particle size (D 50) are 7.0 μm or larger, 7.1 μm or larger, 7.2 μm or larger, 7.3 μm or larger, 7.4 μm or larger, 7.5 μm or larger, 7.6 μm or larger, 7.7 μm or larger, 7.8 μm or larger, 7.9 μm or larger, 8.0 μm or larger, 8.1 μm or larger, 8.2 μm or larger, 8.3 μm or larger, 8.4 μm or larger, 8.5 μm or larger, 8.6 μm or larger, 8.7 μm or larger, 8.8 μm or larger, 8.9 μm or larger, Alternatively, it may be 9.0 μm or larger, and also 20.0 μm or less, 19.9 μm or less, 19.8 μm or less, 19.7 μm or less, 19.6 μm or less, 19.5 μm or less, 19.4 μm or less, 19.3 μm or less, 19.2 μm or less, 19.1 μm or less, 19.0 μm or less, 18.9 μm or less, 18.8 μm or less, 18.7 μm or less, 18.6 μm or less, 18.5 μm or less. Bottom, 18.4μm or less, 18.3μm or less, 18.2μm or less, 18.1μm or less, 18.0μm or less, 17.9μm or less, 17.8μm or less, 17.7μm or less, 17.6μm or less Bottom, 17.5μm or less, 17.4μm or less, 17.3μm or less, 17.2μm or less, 17.1μm or less, 17.0μm or less, 16.9μm or less, 16.8μm or less, 16.7μm or less The thickness may be 16.6 μm or less, 16.5 μm or less, 16.4 μm or less, 16.3 μm or less, 16.2 μm or less, 16.1 μm or less, 16.0 μm or less, 15.9 μm or less, 15.8 μm or less, 15.7 μm or less, 15.6 μm or less, 15.5 μm or less, 15.4 μm or less, 15.3 μm or less, 15.2 μm or less, 15.1 μm or less, or 15.0 μm or less. Within this range, the rolling density of the positive electrode active material can be further improved, and the lifespan can be further improved.

[0045] As a specific example, the positive electrode active material is a high-nickel positive electrode active material containing a lithium transition metal composite oxide in which nickel accounts for 60 mol% or more of the total transition metal, and the multiple primary particles are primary particles with a particle size of 0.5 μm or more and 5.0 μm or less, like conventional single particles, specifically, micron-level primary particles of 1.0 μm or more, and more specifically, the average particle size (D) formed by the aggregation of multiple primary particles with an average particle size of 2.0 μm or more and 3.5 μm or less measured from SEM images. 50It may also contain large-particle secondary particles with a diameter of 7.0 μm or more and 20.0 μm or less, and can be represented as a large-particle single-particle cluster in the sense that primary particles in single-particle form aggregate to form large particles in secondary particle form.

[0046] As described above in the background art of the present invention, in order to manufacture a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level, it is necessary to perform heat treatment at a higher temperature than for secondary particles with primary particle sizes at the submicron level of less than 1 μm. However, the higher the heat treatment temperature, the more the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure, causing a decrease in crystallinity, which in turn degrades the performance of the positive electrode active material. In particular, the degeneration of the layered structure of the lithium transition metal composite oxide into a rock salt structure at high heat treatment temperatures is weakest with respect to nickel, and therefore, the degeneration becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the positive electrode active material is high. Therefore, conventionally, as a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level, it has only been possible to apply this to mid-nickel positive electrode active materials in which the nickel content in the transition metal of the lithium transition metal composite oxide is at the 50 mol level. For high-nickel positive electrode active materials, which have a high nickel content in the transition metal of the lithium transition metal composite oxide and exhibit excellent capacitance characteristics, it has been impossible to manufacture a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level.

[0047] However, the cathode active material of the present invention has a high nickel content among the transition metals of the lithium transition metal composite oxide. Even when the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure at a high heat treatment temperature, the above-mentioned problem is solved by restoring the rock salt structure to a layered structure (recovery). Specifically, the cathode active material of the present invention is a high-nickel cathode active material containing a lithium transition metal composite oxide containing 60 mol% or more of nickel among the total transition metals, different from the conventional mid-nickel cathode active material. It contains secondary particles with a micron-level primary particle size, and restores the rock salt structure formed by a high heat treatment temperature to a layered structure, has excellent crystallinity of the lithium transition metal composite oxide, and can solve the problems of conventional secondary particles and single particles simultaneously. The cathode active material of the present invention can be manufactured by restoring the rock salt structure formed by a high heat treatment temperature to a layered structure as described above. The method for restoring the rock salt structure to a layered structure is not limited. According to one embodiment of the present invention, the method for restoring the rock salt structure to a layered structure may be to perform cobalt (Co) coating on the lithium transition metal composite oxide containing the rock salt structure formed by a high heat treatment temperature.

[0048] According to one embodiment of the present invention, the plurality of primary particles may include disk-shaped (disk type) primary particles. As a specific example, the plurality of primary particles may include three or more disk-shaped (disk type) primary particles. In this case, the cell has excellent life and energy density.

[0049] According to an embodiment of the present invention, the disk-shaped primary particles are primary particles observed from the SEM image of the surface or cross-section of the secondary particles. For two boundary lines of the primary particles existing within an angle of 45° or less with respect to the major axis direction, virtual tangents with the most contact points are drawn respectively. When one virtual line is drawn across the two tangents, the interior angle on the same side is 150° or more and 210° or less, the minor diameter of the primary particle is 0.3 μm or more, and the aspect ratio (major diameter / minor diameter) is 1.5 or more. As a specific example, the minor diameter of the disk-shaped primary particle may be 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1.0 μm or more. Here, when the minor diameter of the disk-shaped primary particle is 0.3 μm or more and the aspect ratio (major diameter / minor diameter) is 1.5 or more, the area ratio of the (003) plane among the crystal planes on the surface portion of the primary particle may be the largest.

[0050] According to an embodiment of the present invention, the disk-shaped primary particles are primary particles observed from the SEM image of the surface or cross-section of the secondary particles. For two boundary lines of the primary particles existing within an angle of 45° or less with respect to the major axis direction, virtual tangents with the most contact points are drawn respectively. When one virtual line is drawn across the two tangents, the interior angle on the same side is 150° or more and 210° or less, and the area ratio of the (003) plane among the crystal planes on the surface portion of the primary particle is the largest. Here, when the area ratio of the (003) plane among the crystal planes on the surface portion of the disk-shaped primary particle is the largest, the minor diameter of the primary particle may be 0.3 μm or more and the aspect ratio (major diameter / minor diameter) may be 1.5 or more. That is, the fact that the area ratio of the (003) plane among the crystal planes on the surface portion of the primary particle is the largest can be confirmed from the fact that the minor diameter of the primary particle is 0.3 μm or more and the aspect ratio (major diameter / minor diameter) is 1.5 or more.

[0051] As a specific example, the positive electrode active material includes secondary particles formed by the aggregation of multiple primary particles, the average particle size of the multiple primary particles measured from SEM images being 1.5 μm or more and 5.0 μm or less, the particle size of the primary particles being based on the major axis of the primary particles, the multiple primary particles including disk-shaped primary particles, the disk-shaped primary particles being observed from SEM images of the surface or cross-section of the secondary particles, where a virtual tangent line with the most points of contact is drawn to two boundary lines of primary particles existing within an angle of 45° or less with respect to the major axis direction, and a virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle being 150° or more and 210° or less, and the area ratio of the (003) plane among the crystal planes on the surface of the primary particles may be the maximum.

[0052] According to one embodiment of the present invention, the positive electrode active material is shown in a frequency distribution graph where the volume cumulative distribution measured using a laser diffraction particle size analyzer is shown on a log scale with the x-axis representing the particle diameter as the x-value increases from left to right, and the y-axis representing the weight distribution as the y-value increases from bottom to top. When a triangle is drawn at the two points of tangency of the frequency distribution curve that are tangent to the peak at the uppermost end of the y-axis of the peak indicated by the mode, and the full width at half maximum (FWHM) of the mode, the interior angle θ at the leftmost point of tangency of the two tangent points of the frequency distribution curve that are tangent to the full width at half maximum is shown. L and the interior angle θ at the right-side point of tangency R The difference θ L -θ R It may be between 6 and 20. For example, the interior angle θ at the left tangency. L and the interior angle θ at the right-side point of tangency R The difference θ L -θ R The ratio θ of the interior angle at the left contact point to the interior angle at the right contact point is 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, or 14 or more, and may also be 20 or less, 19 or less, 18 or less, 17 or less, 16 or less, or 15 or less. L / θ R It may be 1.100 or greater and 2.000 or less. A specific example is the ratio θ of the interior angle at the left tangency to the interior angle at the right tangency. L / θ R If the values ​​are 1.100 or higher, 1.110 or higher, 1.120 or higher, 1.130 or higher, 1.140 or higher, 1.150 or higher, 1.160 or higher, 1.170 or higher, 1.180 or higher, 1.190 or higher, 1.200 or higher, 1.210 or higher, 1.220 or higher, 1.230 or higher, 1.240 or higher, 1.250 or higher, 1.260 or higher, 1.270 or higher, 1.280 or higher, 1.290 or higher, 1.300 or higher, 1.310 or higher, 1.320 or higher, 1.330 or higher, 1.340 or higher, 1.350 or higher, 1.360 or higher It may be 1.370 or higher, 1.380 or higher, 1.390 or higher, 1.400 or higher, 1.410 or higher, 1.420 or higher, 1.430 or higher, or 1.440 or higher, and it may also be 1.450 or lower, 1.460 or lower, 1.470 or lower, 1.480 or lower, 1.490 or lower, 1.500 or lower, 1.550 or lower, 1.600 or lower, 1.650 or lower, 1.700 or lower, 1.750 or lower, 1.800 or lower, 1.850 or lower, 1.900 or lower, 1.950 or lower, or 2.000 or lower. Here, the frequency distribution graph may be a unimodal distribution graph.

[0053] According to one embodiment of the present invention, the positive electrode active material may exhibit positive skewness in a frequency distribution graph in which the volume cumulative distribution measured using a laser diffraction particle size analyzer is shown, with the x-axis representing particle diameters increasing from left to right on a linear scale, and the y-axis representing weight distributions increasing from bottom to top on a y-axis. Here, the frequency distribution graph may be a unimodal distribution graph.

[0054] According to one embodiment of the present invention, the positive electrode active material is the y-value P of the uppermost peak point on the y-axis of the peak indicated by the mode of the volume cumulative distribution. MODE The ratio of the skewness value S to the ratio S / P MODE The value may be 0.037 or greater and 0.150 or less. Specifically, the positive electrode active material is the y value P of the uppermost peak point on the y axis of the peak shown by the mode value Mode of the volume cumulative distribution. MODE The ratio of the skewness value S to the ratio S / P MODEHowever, 0.037 or higher, 0.038 or higher, 0.039 or higher, 0.040 or higher, 0.041 or higher, 0.042 or higher, 0.043 or higher, 0.044 or higher, 0.045 or higher, 0.046 or higher, 0.047 or higher, 0.048 or higher, 0.049 or higher, 0.050 or higher, 0.051 or higher, 0.052 or higher, 0.053 or higher, 0.054 or higher , 0.055 or higher, 0.056 or higher, 0.057 or higher, 0.058 or higher, 0.059 or higher, 0.060 or higher, 0.061 or higher, 0.062 or higher, 0.063 or higher, 0.064 or higher, 0.065 or higher, 0.066 or higher, 0.067 or higher, 0.068 or higher, 0.069 or higher, 0.070 or higher, 0.071 or higher, 0.072 or higher, 0 It may be 0.073 or higher, 0.074 or higher, 0.075 or higher, 0.076 or higher, 0.077 or higher, 0.078 or higher, 0.079 or higher, 0.080 or higher, 0.081 or higher, 0.082 or higher, 0.083 or higher, 0.083 or higher, 0.084 or higher, 0.085 or higher, 0.086 or higher, 0.087 or higher, 0.088 or higher, 0.089 or higher, 0.090 or higher, 0.091 or higher, 0.092 or higher, 0.093 or higher, 0.094 or higher, 0.095 or higher, 0.096 or higher, 0.097 or higher, 0.098 or higher, 0.099 or higher, or 0.100 or higher, and may also be 0.150 or lower, 0.140 or lower, 0.130 or lower, 0.120 or lower, or 0.110 or lower. Here, the skewness value S may be calculated by the following equation 3.

[0055]

number

[0056] According to one embodiment of the present invention, the positive electrode active material has a BET specific surface area of ​​0.20 m² as measured by nitrogen adsorption BET specific surface area analysis. 2 / g or more, 0.35m 2 It may be less than or equal to / g. As a specific example, the positive electrode active material has a BET specific surface area of ​​0.20 m² as measured by nitrogen adsorption BET specific surface area analysis. 2 / g or more, 0.21m 2 / g or more, 0.22m 2 / g or more, 0.23m 2 / g or more, 0.24m2 / g or more, 0.25m 2 / g or more, 0.26m 2 / g or more, 0.27m 2 / g or more, 0.28m 2 / g or more, 0.29m 2 / g or more, 0.30m 2 / g or more, or 0.31m 2 It may be 0.35m or more, and also 0.35m 2 Less than / g, or 0.34m 2 It may be less than / g. Within this range, DC resistance can be reduced and rolling density can be improved.

[0057] According to one embodiment of the present invention, the positive electrode active material has an average particle size (D) determined by the volume cumulative distribution measured with a laser diffraction particle size analyzer for the secondary particles. 50 The size of the secondary particle cross-section is 7.0 μm or larger and 20.0 μm or smaller, and the size of the secondary particle cross-section observed from the SEM image of the secondary particle cross-section is equal to the average particle size (D) of the secondary particle. 50 For a cross-section of a secondary particle having a size within the specified range, the number of primary particle cross-sections observed within a unit area of ​​5 μm x 5 μm in the cross-section of the secondary particle may be one or more and 100 or less.

[0058] According to one embodiment of the present invention, the size of the cross-section of the secondary particle observed from the SEM image of the cross-section of the secondary particle is the average particle size (D 50 For a cross-section of a secondary particle having a size within the specified range, the number of primary particle cross-sections observed within a unit area of ​​5 μm x 5 μm within the cross-section of the secondary particle means the number of primary particle cross-sections that are included in the unit area, as well as the number of primary particle cross-sections that are included in at least a portion of the unit area. Furthermore, the unit area of ​​5 μm x 5 μm within the cross-section of the secondary particle is the unit area at any point within the cross-section of the secondary particle, and the position is not restricted as long as it is within the cross-section of the secondary particle.

[0059] According to one embodiment of the present invention, the positive electrode active material is such that the size of the cross-section of the secondary particles, as observed from the SEM image of the cross-section of the secondary particles, is equal to the average particle size (D) of the secondary particles.50 For a cross-section of a secondary particle having a size within the range, the number of primary particle cross-sections observed within a unit area of ​​5 μm x 5 μm in the cross-section of the secondary particle may be 1 or more and 100 or less. For example, it may be 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more. It may also be 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, or 25 or less. If such a range is met, the positive electrode active material is a material in which multiple primary particles are aggregated to form an average particle size (D) such that multiple primary particles have a particle size of 0.5 μm or more and 5.0 μm or less, similar to conventional single particles, specifically micron-level primary particles of 1.0 μm or more, or more specifically, multiple primary particles with an average particle size of 2.0 μm or more and 3.5 μm or less, as measured from SEM images. 50 It can be shown that the product contains large-particle secondary particles with a size of 7.0 μm or more and 20.0 μm or less.

[0060] According to one embodiment of the present invention, the positive electrode active material has an average particle size (D) determined by the volume cumulative distribution measured with a laser diffraction particle size analyzer for the secondary particles. 50 The size of the secondary particle cross-section is 7.0 μm or larger and 20.0 μm or smaller, and the size of the secondary particle cross-section is observed from the electron backscatter diffraction (EBSD) pattern of the SEM image of the secondary particle cross-section (measured under the conditions of acceleration voltage 20 kV, WD 16 mm, measurement magnification 5,000x (width 16 μm × height 16 μm), step size 0.025 μm), which indicates that the average particle size (D) of the secondary particle is 7.0 μm or larger and 20.0 μm or smaller. 50 For a cross-section of a secondary particle having a size within the specified range, the number of grain cross-sections observed within a unit area of ​​5 μm x 5 μm in the cross-section of the secondary particle may be 1 or more and 150 or less.

[0061] According to one embodiment of the present invention, the size of the cross-section of a secondary particle is observed from the electron backscatter diffraction (EBSD) pattern of a SEM image of the cross-section of a secondary particle (measured under the conditions of acceleration voltage 20kV, WD 16mm, measurement magnification 5,000x (width 16μm × height 16μm), and step size 0.025μm), and the average particle size (D) of the secondary particle is observed from the electron backscatter diffraction (EBSD) pattern of the cross-section of the secondary particle. 50 For a cross-section of a secondary particle having a size within the specified range, the number of grain cross-sections observed within a unit area of ​​5 μm x 5 μm within the cross-section of the secondary particle means the number of all grain cross-sections that are included within the unit area, as well as the number of grain cross-sections that are included in at least part of the unit area. Furthermore, the unit area of ​​5 μm x 5 μm within the cross-section of the secondary particle is the unit area at any point within the cross-section of the secondary particle, and the position is not restricted as long as it is within the cross-section of the secondary particle.

[0062] According to one embodiment of the present invention, the positive electrode active material is such that the size of the cross-section of the secondary particles is observed from the electron backscatter diffraction (EBSD) pattern of the cross-section of the secondary particles (measured under the conditions of acceleration voltage 20kV, WD 16mm, measurement magnification 5,000x (width 16μm × height 16μm), step size 0.025μm), and the size of the cross-section of the secondary particles is the average particle size (D) of the secondary particles. 50For a cross-section of a secondary particle having a size within the range, the number of grain cross-sections observed within a unit area of ​​5 μm x 5 μm in the cross-section of the secondary particle may be 1 or more and 150 or less. Specifically, it may be 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, or 9 or more. It may also be 150 or less, 145 or less, 140 or less, 135 or less, 130 or less, 125 or less, 120 or less, 115 or less, 110 or less, 105 or less, 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, or 20 or less. If such a range is met, the positive electrode active material is a material in which multiple primary particles are aggregated to form an average particle size (D) such that multiple primary particles have a particle size of 0.5 μm or more and 5.0 μm or less, like conventional single particles, specifically, micron-level primary particles of 1.0 μm or more, or more specifically, multiple primary particles with an average particle size of 2.0 μm or more and 3.5 μm or less, as measured from SEM images. 50 It can be shown that the product contains large-particle secondary particles with a size of 7.0 μm or more and 20.0 μm or less.

[0063] According to one embodiment of the present invention, the positive electrode active material has a single crystallinity of 0.15 μm, calculated by the following formula 1. 3 That's fine too.

[0064]

number

[0065] In equation 1 above, radius(grain) is the size of the cross-section of the secondary particle observed from the electron backscatter diffraction (EBSD) pattern on the SEM image of the cross-section of the secondary particle (measured under the conditions of acceleration voltage 20kV, WD 16mm, measurement magnification 5,000x (width 16μm × height 16μm), and step size 0.025μm), where the average particle size (D) of the secondary particle is the size of the cross-section of the secondary particle. 50Of all the cross-sections of grains observable in the cross-section of secondary particles having a size within the range, the radius of the cross-section of the grain when assuming that the cross-section of the grain is circular, where the area of the cross-section of the grain is 0.196 μm 2 or more, and n is the number of grains.

[0066] According to one embodiment of the present invention, the positive electrode active material has a crystallinity calculated by the above formula (1) of 0.15 μm 3 or more and 12.70 μm 3 or less. As a specific example, the positive electrode active material has a crystallinity calculated by the above formula (1) of 0.15 μm 3 or more and 0.20 μm 3 or more and 0.25 μm 3 or more and 0.30 μm 3 or more and 0.35 μm 3 or more and 0.40 μm 3 or more and 0.45 μm 3 or more and 0.50 μm 3 or more and 0.55 μm 3 or more and 0.60 μm 3 or more and 0.65 μm 3 or more and 0.70 μm 3 or more and 0.75 μm 3 or more and 0.80 μm 3 or more and 0.85 μm 3 or more and 0.9 0 μm 3 or more and 0.95 μm 3 or more and 1.00 μm 3 or more and 1.05 μm 3 or more, and the upper limit is not particularly limited, but 20.00 μm 3 or less, 19.00 μm 3 or less, 18.00 μm 3 or less, 17.00 μm 3 or less, 16.00 μm 3 or less, 15.00 μm 3 or less, 14.00 μm 3 or less, 13.00 μm 3 or less, or 12.70 μm 3 or less.

[0067] According to an embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide containing aluminum (Al), yttrium (Y), and zirconium (Zr). As a specific example, the positive electrode active material may include aluminum (Al), yttrium (Y), and zirconium (Zr) as doping elements.

[0068] According to an embodiment of the present invention, the aluminum (Al) may be contained at a content of 500 ppm to 3,000 ppm with respect to the total weight of the lithium transition metal composite oxide. As a specific example, the aluminum (Al) may be contained at a content of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more with respect to the total weight of the lithium transition metal composite oxide, and may also be contained at a content of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0069] According to an embodiment of the present invention, the yttrium (Y) may be contained at a content of 100 ppm to 2,000 ppm with respect to the total weight of the lithium transition metal composite oxide. As a specific example, the yttrium (Y) may be contained at a content of 100 ppm or more, 200 ppm or more, 300 ppm or more, 400 ppm or more, or 500 ppm or more with respect to the total weight of the lithium transition metal composite oxide, and may also be contained at a content of 2,000 ppm or less, 1,900 ppm or less, 1,800 ppm or less, 1,700 ppm or less, 1,600 ppm or less, or 1,500 ppm or less.

[0070] According to an embodiment of the present invention, the zirconium (Zr) may be contained at a content of 500 ppm to 5,000 ppm with respect to the total weight of the lithium transition metal composite oxide. As a specific example, the zirconium (Zr) may be contained at a content of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more with respect to the total weight of the lithium transition metal composite oxide, and may also be contained at a content of 5,000 ppm or less, 4,500 ppm or less, 4,000 ppm or less, 3,500 ppm or less, or 3,000 ppm or less.

[0071] According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide having an average composition represented by the following chemical formula 2.

[0072] [Chemical formula 2] Li x [Ni a Co b Mn c Al e Y f Zr g M 2 d ]O 2-y A y

[0073] In the above chemical formula 2, M 2 a is one or more elements selected from the group consisting of B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, and A is one or more elements selected from the group consisting of F, Cl, Br, I, and S, with 0.9≦x≦1.3, 0.6≦a<1.0, 0 <b<0.4、0<c<0.4、0≦d≦0.2、0<e≦0.01、0<f≦0.0006、0<g≦0.0005、a+b+c+d+e+f+g=1、0≦y≦0.2である。

[0074] According to one embodiment of the present invention, in the chemical formula 2, x is the molar ratio of lithium to the transition metal in the lithium transition metal composite oxide, and may be 0.9 or more, 0.95 or more, or 1.0 or more, and may also be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0075] According to one embodiment of the present invention, in the chemical formula 2, a, b, c, d, e, f, and g are, respectively, nickel (Ni), cobalt (Co), manganese (Mn), and doping element (M 2), aluminum (Al), yttrium (Y), and zirconium (Zr) may also be mole fractions. Specifically, a is the mole fraction of nickel (Ni) among the transition metals, and may be 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, 0.88 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, or 0.96 or more, and may also be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. Furthermore, b is the mole fraction of cobalt (Co) among the transition metals, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. c is the mole fraction of manganese (Mn) among the transition metals, and may be greater than 0, 0.01 or more, or 0.05 or more, and may also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. d is the mole fraction of the doping element (Mn) among the transition metals. 2This is the mole fraction of 0, and may be 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, or 0.19 or more. Furthermore, it may be less than 0.20, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. The above e is the mole fraction of aluminum (Al) among the transition metals, and may be greater than 0, 0.001 or more, 0.002 or more, 0.003 or more, 0.004 or more, or 0.005 or more, and may also be 0.01 or less, 0.009 or less, or 0.008 or less. The aforementioned f is the mole fraction of yttrium (Y) among the transition metals, and may be greater than 0, 0.0001 or more, 0.0002 or more, or 0.0003 or more, and may also be 0.0006 or less, 0.0005 or less, or 0.0004 or less. The aforementioned g is the mole fraction of zirconium (Zr) among the transition metals, and may be greater than 0, 0.0001 or more, or 0.0002 or more, and may also be 0.0005 or less, or 0.0004 or less.

[0076] According to one embodiment of the present invention, in the chemical formula 2, y is the molar ratio of element A substituted with oxygen in the lithium transition metal composite oxide, and may be 0, greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, or 0.2 or less, 0.15 or less, or 0.1 or less.

[0077] According to one embodiment of the present invention, the positive electrode active material is aluminum (Al), zirconium (Zr), and M 3 The lithium transition metal composite oxide may also include aluminum (Al), zirconium (Zr), and M. 3 It may contain as a doping element.

[0078] According to one embodiment of the present invention, the M 3 This may be a metallic element with an oxidation state of +4 or higher. For example, the above M 3 This may be one or more elements selected from the group consisting of titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo), and niobium (Nb).

[0079] According to one embodiment of the present invention, the aluminum (Al) may be present in a content of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal composite oxide. Specifically, the aluminum (Al) may be present in a content of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more relative to the total weight of the lithium transition metal composite oxide, or in a content of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0080] According to one embodiment of the present invention, the zirconium (Zr) may be present in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal composite oxide. Specifically, the zirconium (Zr) may be present in an amount of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more relative to the total weight of the lithium transition metal composite oxide, or in an amount of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0081] According to one embodiment of the present invention, the M 3 It may be included in an amount of 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal composite oxide. For example, the M 3It may be included in a content of 100 ppm or more, 200 ppm or more, 300 ppm or more, 400 ppm or more, or 500 ppm or more relative to the total weight of the lithium transition metal composite oxide, or in a content of 2,000 ppm or less, 1,900 ppm or less, 1,800 ppm or less, 1,700 ppm or less, 1,600 ppm or less, or 1,500 ppm or less.

[0082] According to one embodiment of the present invention, the positive electrode active material includes a coating portion formed on at least one of the surfaces of primary particles, the interfaces of primary particles, and the surfaces of secondary particles, and the coating portion may include one or more coating elements selected from the group consisting of cobalt (Co) and boron (B).

[0083] According to one embodiment of the present invention, the coating portion may be an island-shaped coating portion formed on a part of at least one of the surfaces of primary particles, interfaces of primary particles, and surfaces of secondary particles.

[0084] According to one embodiment of the present invention, the coating portion may be a coating layer formed to cover at least one of the surfaces of primary particles, the interfaces of primary particles, and the surfaces of secondary particles.

[0085] According to one embodiment of the present invention, the coating portion may include at least one of the following coating portions: a coating portion containing cobalt (Co), a coating portion containing cobalt (Co) and boron (B), and a coating portion containing boron (B).

[0086] According to one embodiment of the present invention, the coating portion may include a coating portion in which a coating portion containing cobalt (Co), a coating portion containing cobalt (Co) and boron (B), and a coating portion containing boron (B) are formed in sequence.

[0087] According to one embodiment of the present invention, the coating portion may contain cobalt-boron oxide.

[0088] According to one embodiment of the present invention, when the positive electrode active material is placed into a cylindrical mold with a diameter of 13 mm using an automatic pellet press and pressure is applied until a force equivalent to 9,000 kgf is reached to form pellets, the rolling density calculated by the following formula 2 is 3.60 g / cm³. 3 That's fine too.

[0089] [Formula 2] Rolling density (g / cm³) 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm³) 3 )

[0090] According to one embodiment of the present invention, the positive electrode active material has a rolling density of 3.60 g / cm³ calculated by formula 2. 3 It may be greater than or equal to the above, and as a specific example, 3.61 g / cm³ 3 More than 3.62g / cm 3 More than 3.63g / cm 3 More than 3.64g / cm 3 More than 3.65g / cm 3 More than 3.66g / cm 3 More than 3.67g / cm 3 Above, 3.68g / cm 3 More than 3.69g / cm 3 More than 3.70g / cm 3 Above, or 3.71 g / cm³ 3 It may be greater than or equal to 10.0 g / cm³, and there is no particular upper limit, but it is 10.0 g / cm³. 3 The following is also acceptable.

[0091] According to one embodiment of the present invention, the positive electrode active material may be such that, for a lithium secondary battery comprising a positive electrode containing the positive electrode active material, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, the discharge capacity when the lithium secondary battery is charged with a current of 0.5C and then discharged with a current of 0.1C is used as a reference, and the discharge capacity when the lithium secondary battery is charged with a current of 0.5C and then discharged with a current of 1.0C is 92.0% or more. Here, the lithium secondary battery is for confirming the discharge capacity based on the output characteristics of the positive electrode active material, and the components other than the positive electrode active material are not particularly limited as long as they can be used in a lithium secondary battery. As a specific example, the positive electrode active material may have a discharge capacity of 92.0% or more, 92.1% or more, 92.2% or more, 92.3% or more, 92.4% or more, 92.5% or more, 92.6% or more, 92.7% or more, 92.8% or more, 92.9% or more, 93.0% or more, or 93.1% or more, based on the discharge capacity when the lithium secondary battery is charged with a current of 0.5C and then discharged with a current of 0.1C, and there is no particular upper limit, but it may be 100% or less.

[0092] According to one embodiment of the present invention, the positive electrode active material may be such that, for a lithium secondary battery comprising a positive electrode containing the positive electrode active material, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, the discharge capacity when the lithium secondary battery is charged with a current of 0.5C and then discharged with a current of 0.1C is used as a reference, and the discharge capacity when the lithium secondary battery is charged with a current of 0.5C and then discharged with a current of 2.0C is 89.0% or more. Here, the lithium secondary battery is for confirming the discharge capacity based on the output characteristics of the positive electrode active material, and the components other than the positive electrode active material are not particularly limited as long as they can be used in a lithium secondary battery. As a specific example, the positive electrode active material may have a discharge capacity of 89.0% or more, 89.1% or more, 89.2% or more, 89.3% or more, 89.4% or more, 89.5% or more, 89.6% or more, 89.7% or more, 89.8% or more, 89.9% or more, 90.0% or more, 90.1% or more, 90.2% or more, 90.3% or more, or 90.4% or more, with no particular upper limit, although it may be 100% or less.

[0093] According to one embodiment of the present invention, the positive electrode active material is such that when the volume of each primary particle observed from an SEM image (measurement magnification 3,000x) of the surface of the secondary particles is calculated using the following formula 5, the degree of single-particle formation (Dv) corresponds to the diameter of the volume at the point where the cumulative volume distribution of the primary particles reaches 50%. 50 The diameter may be between 1.2 μm and 3.8 μm.

[0094]

number

[0095] In the above formula 5, The radius is the radius of the primary particle's surface, assuming that the primary particle's surface is circular, as observed from the SEM image of the secondary particle's surface (measurement magnification 3,000x).

[0096] As a specific example, the positive electrode active material has a single-particle degree (Dv 50 The diameter may be 1.2 μm or larger, 1.3 μm or larger, 1.4 μm or larger, 1.5 μm or larger, 1.6 μm or larger, or 1.65 μm or larger, and may also be 3.8 μm or smaller, 3.7 μm or smaller, 3.6 μm or smaller, 3.59 μm or smaller, 3.58 μm or smaller, 3.57 μm or smaller, 3.56 μm or smaller, or 3.55 μm or smaller.

[0097] Method for manufacturing positive electrode active material This invention provides a method for producing a positive electrode active material.

[0098] According to one embodiment of the present invention, the method for producing the positive electrode active material may be a method for producing the above-mentioned positive electrode active material.

[0099] According to one embodiment of the present invention, the method for producing the positive electrode active material may include the step (S10) of mixing a positive electrode active material precursor containing nickel, cobalt, and manganese with a lithium raw material and performing calcination to produce a calcined product.

[0100] According to one embodiment of the present invention, step (S10) can be carried out by methods such as a method in which firing is performed by dividing the temperature interval within a single firing step (one-step method), a method in which firing is performed by dividing the temperature interval within a single firing step (two-step method), and a method in which pre-firing is performed before firing is performed by dividing the temperature interval within a single firing step (pre-firing method).

[0101] According to one embodiment of the present invention, the one-step method is a method of performing calcination in succession in two temperature intervals within a single calcination step, in which a first-stage calcination is performed on a mixture of a positive electrode active material precursor and a lithium raw material, and then a second-stage calcination is performed by changing the temperature interval. Here, the second-stage calcination can be performed at a lower temperature than the first-stage calcination, and each calcination temperature can be adjusted according to the nickel content, and by adjusting the temperature in this way, the morphology and size of the primary particles and the average particle size of the secondary particles can be adjusted.

[0102] According to one embodiment of the present invention, the two-step method is a method carried out in two stages: primary calcination and secondary calcination. Primary calcination is performed on a mixture of a positive electrode active material precursor and a lithium raw material. The first calcined product produced by the primary calcination is then pulverized, and the pulverized product is then subjected to secondary calcination. Here, the secondary calcination can be carried out at a lower temperature than the primary calcination, and each calcination temperature can be adjusted according to the nickel content. By adjusting the temperature in this way, the morphology and size of the primary particles and the average particle size of the secondary particles can be adjusted.

[0103] According to one embodiment of the present invention, the calcination method is a method of performing calcination before one-step calcination, and the calcination is performed on a mixture of positive electrode active material precursor and lithium raw material, and the one-step method can be performed on the calcined product. Here, the calcination can be performed at a lower temperature than the one-step calcination, and each calcination temperature can be adjusted according to the nickel content, and by adjusting the temperature in this way, the morphology and size of the primary particles and the average particle size of the secondary particles can be adjusted.

[0104] According to one embodiment of the present invention, the positive electrode active material precursor may contain 60 mol% or more of nickel among the transition metals. Specifically, the positive electrode active material precursor may be a transition metal hydroxide containing nickel, cobalt, and manganese, and containing 60 mol% or more of nickel among the transition metals. Specifically, the transition metal hydroxide may have an average composition represented by the following chemical formula 3.

[0105] [Chemical formula 3] Ni a’ Co b’ Mn c’ (OH)2

[0106] In the above chemical formula 3, 0.6 ≤ a' < 1.0, 0 <b’<0.4、0<c’<0.4、a’+b’+c’=1である。

[0107] According to one embodiment of the present invention, in the chemical formula 3, a', b', and c' may be the mole fractions of nickel (Ni), cobalt (Co), and manganese (Mn), respectively, among the transition metals. Specifically, a' is the mole fraction of nickel (Ni) among the transition metals, and may be 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, 0.88 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, or 0.96 or more, or it may be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. Furthermore, b' is the mole fraction of cobalt (Co) among the transition metals, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. c' is the mole fraction of manganese (Mn) among the transition metals, and may be greater than 0, 0.01 or more, or 0.05 or more, and may also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less.

[0108] According to one embodiment of the present invention, the lithium raw material can be lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, hydroxides, or oxyhydroxides, for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or mixtures thereof.

[0109] According to one embodiment of the present invention, step (S10) may further include one or more doping materials selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y. The doping materials may be acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, or oxyhydroxides containing the elements, and specific examples may include Al2O3, Al(OH)3, Al(NO3)3·9H2O, Al2(SO4)3, Y2O3, ZrO2, etc.

[0110] According to one embodiment of the present invention, the doping material may include Al, Y, and Zr. Furthermore, the doping material may include Al, Zr, and a metal element (M) with an oxidation state of +4 or higher. 3 ) may be included.

[0111] According to one embodiment of the present invention, in step (S10), when mixing the positive electrode active material precursor and the lithium raw material, the molar ratio (Li / M) of lithium (Li) in the lithium raw material to the transition metal (M) in the positive electrode active material precursor may be 0.9 or more and 1.3 or less. Specifically, the Li / M may be 0.9 or more, 0.95 or more, or 1.0 or more, or 1.1 or less, 1.07 or less, 1.05 or less, or 1.04 or less, and the Li / M can be adjusted according to the nickel content in the transition metal.

[0112] According to one embodiment of the present invention, the method for producing the positive electrode active material may further include a step (S20) of coating the positive electrode active material produced in step (S10). Specifically, step (S20) may be carried out by including one or more coating raw materials selected from the group consisting of Co and B. Alternatively, step (S20) may be carried out by further including an Al coating raw material.

[0113] According to one embodiment of the present invention, the coating in step (S20) may be carried out by simultaneously coating each coating raw material, or by sequentially coating them. Specifically, the coating in step (S20) may include a step (S21) in which a Co coating raw material and an Al coating raw material are mixed with the positive electrode active material and heat-treated, and a step (S22) in which a B coating raw material is mixed with the coated product produced in step (S21) and heat-treated.

[0114] According to one embodiment of the present invention, the Co coating raw material may be a cobalt hydroxide such as Co(OH)2, the Al coating raw material may be an aluminum hydroxide such as Al(OH)3, and the B coating raw material may be H3BO3.

[0115] According to one embodiment of the present invention, the method for producing the positive electrode active material may include, when carrying out steps (S10) and (S20), a step of crushing the fired product after firing, if necessary, and the crushing may be carried out using any crushing apparatus capable of crushing the positive electrode active material, without any particular limitations.

[0116] According to one embodiment of the present invention, the doping raw material and the coating raw material can be added in an adjusted manner to satisfy the content of the doping element and the content of the coating element of the positive electrode active material.

[0117] positive electrode The present invention provides a positive electrode containing the positive electrode active material.

[0118] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0119] According to one embodiment of the present invention, the positive electrode current collector can contain a highly conductive metal, is not particularly limited as long as the positive electrode active material layer adheres easily to it, and is unreactive within the battery voltage range. The positive electrode current collector can be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment using carbon, nickel, titanium, silver, etc. The positive electrode current collector can also typically have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc.

[0120] According to one embodiment of the present invention, the positive electrode active material layer may optionally include a conductive material and a binder together with the positive electrode active material. Here, the positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, relative to the total weight of the positive electrode active material layer, and within this range, excellent capacitance characteristics can be observed.

[0121] According to one embodiment of the present invention, the conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in a battery that does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Of these, one or more can be used. The conductive material can be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0122] According to one embodiment of the present invention, the binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which the hydrogen atoms of these are substituted with Li, Na, or Ca, or various copolymers thereof. One of these alone or a mixture of two or more can be used. The binder can be present in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0123] According to one embodiment of the present invention, the positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode active material is used. Specifically, the positive electrode can be manufactured by coating a positive electrode active material layer-forming composition, which is prepared by dissolving or dispersing the positive electrode active material and, if necessary, selectively, a binder, a conductive material, and a dispersant in a solvent, onto a positive electrode current collector, and then drying and rolling it; or by casting the positive electrode active material layer-forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0124] According to one embodiment of the present invention, the solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more can be used. The amount of solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode.

[0125] Lithium-ion battery The present invention provides a lithium secondary battery including the positive electrode.

[0126] According to one embodiment of the present invention, the lithium secondary battery may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The lithium secondary battery may also optionally further include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0127] According to one embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0128] According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The negative electrode current collector can also typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0129] According to one embodiment of the present invention, the negative electrode active material layer may selectively include a binder and a conductive material together with the negative electrode active material.

[0130] According to one embodiment of the present invention, the negative electrode active material can be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include metallic oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more mixtures thereof can be used. A metallic lithium thin film can also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbons such as petroleum or coal tar pitch-derived cokes. The anode active material can be present in an amount of 80% to 99% by weight relative to the total weight of the anode active material layer.

[0131] According to one embodiment of the present invention, the binder of the negative electrode active material layer is a component that helps to bond the conductive material, the active material, and the current collector, and is usually added in an amount of 0.1% to 10% by weight relative to the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0132] According to one embodiment of the present invention, the conductive material in the negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and can be added in an amount of 10% by weight or less, preferably 5% by weight or less, relative to the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0133] According to one embodiment of the present invention, the negative electrode can be manufactured by coating a negative electrode active material layer-forming composition, which is prepared by dissolving or dispersing a negative electrode active material and, selectively, a binder and a conductive material in a solvent, onto a negative electrode current collector and drying the coating, or by casting the negative electrode active material layer-forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0134] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is a separator that is normally used in lithium secondary batteries, and it is especially preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. In addition, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and may be used selectively in a single-layer or multi-layer structure.

[0135] According to one embodiment of the present invention, the electrolyte can be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, which can be used in the manufacture of lithium secondary batteries, and is not limited to these. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0136] According to one embodiment of the present invention, the organic solvent can be used without particular limitations as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0137] According to one embodiment of the present invention, the lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt is F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - The lithium salt may be selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably in the range of 0.1M to 2.0M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0138] According to one embodiment of the present invention, in addition to the components of the electrolyte, the electrolyte may further contain one or more additives for the purpose of improving the battery life characteristics, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride. Here, the additive may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0139] The lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent capacity characteristics, output characteristics, and life characteristics in a stable manner, making it useful in fields such as portable devices like mobile phones, notebook computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0140] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-type, or coin-type, using a can.

[0141] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also preferably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0142] Thus, according to one embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0143] According to one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0144] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0145] Examples The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only and do not limit the scope of the present invention to these examples alone.

[0146] Example 1 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.04. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0147] The mixture was calcined in an oxygen atmosphere at 850°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8833 Co 0.0298 Mn 0.0794Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0148] A mixture was prepared by adding Al(OH)2 to the lithium transition metal oxide in secondary particle form produced above, at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and then uniformly mixing the mixture. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Y 0.0010 Zr 0.0015 It was O2.

[0149] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Y 0.0010 Zr 0.0015 B0.0045 It was O2.

[0150] Example 2 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.00. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0151] The mixture was subjected to primary calcination at 850°C for 6 hours under an oxygen atmosphere to obtain a first calcined product. Subsequently, the first calcined product was subjected to an average particle size (D) test at room temperature. 50 The particles were ground to a size of 9.8 μm.

[0152] The pulverized primary calcined product was mixed with LiOH such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 0.04, and the mixture was subjected to secondary calcination at 800°C for 9 hours under an oxygen atmosphere to obtain a second calcined product. The second calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0153] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Y 0.0010 Zr 0.0015 It was O2.

[0154] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0155] Example 3 Ni 0.89 Co 0.03Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.04. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0156] The mixture was calcined at 550°C for 5 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was then subjected to a temperature check at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 9.8 μm.

[0157] The pulverized calcined product was calcined in an oxygen atmosphere at 850°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was then pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0158] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Y 0.0010 Zr 0.0015 It was O2.

[0159] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0160] Example 4 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.04. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0161] The mixture was calcined in an oxygen atmosphere at 880°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0162] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Y 0.0010 Zr 0.0015 It was O2.

[0163] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0164] Example 5 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) (10.2 μm) and LiOH was prepared such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.04. Al(OH)3 was added to this mixture at concentrations of 1,470 ppm, Y2O3 at 2,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0165] The mixture was calcined in an oxygen atmosphere at 850°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8824 Co 0.0297 Mn 0.0793 Al 0.0050 Y 0.0021 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0166] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8632 Co 0.0491 Mn 0.0776 Al 0.0066 Y 0.0020 Zr 0.0015 It was O2.

[0167] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8593 Co 0.0489 Mn 0.0772 Al 0.0066 Y 0.0020 Zr 0.0015 B 0.0045 It was O2.

[0168] Example 6 Ni 0.89 Co 0.03Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.04. Al(OH)3 was added at concentrations of 2,940 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0169] The mixture was calcined in an oxygen atmosphere at 850°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8789 Co 0.0296 Mn 0.0790 Al 0.0100 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0170] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8597 Co 0.0490 Mn 0.0773 Al 0.0115 Y 0.0010 Zr 0.0015It was O2.

[0171] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8559 Co 0.0488 Mn 0.0769 Al 0.0115 Y 0.0010 Zr 0.0014 B 0.0045 It was O2.

[0172] Example 7 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) (10.2 μm) and LiOH was prepared such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.04. Al(OH)3 was added to this mixture at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 3,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0173] The mixture was calcined in an oxygen atmosphere at 850°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8815 Co 0.0297 Mn 0.0793 Al 0.0050 Y 0.0010 Zr 0.0035A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0174] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8623 Co 0.0491 Mn 0.0775 Al 0.0066 Y 0.0010 Zr 0.0035 It was O2.

[0175] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8584 Co 0.0489 Mn 0.0772 Al 0.0066 Y 0.0010 Zr 0.0034 B 0.0045 It was O2.

[0176] Example 8 Ni 0.96 Co 0.03 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (14.5 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.02. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0177] The mixture was calcined in an oxygen atmosphere at 800°C for 6 hours, and then at 760°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 14.2 μm, LiNi 0.9528 Co 0.0298 Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0178] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 700°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50The primary particles were crushed to a size of 14.5 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9320 Co 0.0491 Mn 0.0097 Al 0.0067 Y 0.0010 Zr 0.0015 It was O2.

[0179] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 14.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9278 Co 0.0489 Mn 0.0097 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0180] Example 9 Ni 0.96 Co 0.03 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (14.5 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 0.98. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0181] The mixture was subjected to primary calcination at 800°C for 6 hours under an oxygen atmosphere to obtain a first calcined product. Subsequently, the first calcined product was subjected to an average particle size (D) test at room temperature. 50 The particles were ground to a size of 14.2 μm.

[0182] The pulverized primary calcined product was mixed with LiOH such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 0.04, and the mixture was subjected to secondary calcination at 760°C for 9 hours under an oxygen atmosphere to obtain a second calcined product. The second calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 14.2 μm, LiNi 0.9528 Co 0.0298 Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0183] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 700°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The primary particles were crushed to a size of 14.5 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9320 Co 0.0491 Mn 0.0097 Al 0.0067 Y 0.0010 Zr 0.0015 It was O2.

[0184] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 14.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9278 Co 0.0489 Mn 0.0097 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0185] Example 10 Ni 0.96 Co 0.03 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (14.5 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.02. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0186] The mixture was calcined at 550°C for 5 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was then subjected to a temperature check at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 14.2 μm.

[0187] The pulverized calcined product was calcined in an oxygen atmosphere at 800°C for 6 hours, and then at 760°C for 9 hours to obtain a calcined product. The calcined product was then pulverized at room temperature to obtain an average particle size (D 50 ) is 14.2 μm, LiNi 0.9528 Co 0.0298Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0188] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 700°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The primary particles were crushed to a size of 14.5 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9320 Co 0.0491 Mn 0.0097 Al 0.0067 Y 0.0010 Zr 0.0015 It was O2.

[0189] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 14.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9278 Co 0.0489 Mn 0.0097 Al 0.0066 Y 0.0010 Zr0.0015 B 0.0045 It was O2.

[0190] Example 11 Ni 0.96 Co 0.03 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (14.5 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.02. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0191] The mixture was calcined in an oxygen atmosphere at 830°C for 6 hours, and then at 760°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 14.2 μm, LiNi 0.9528 Co 0.0298 Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0192] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 700°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50The primary particles were crushed to a size of 14.5 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9320 Co 0.0491 Mn 0.0097 Al 0.0067 Y 0.0010 Zr 0.0015 It was O2.

[0193] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 14.2 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9278 Co 0.0489 Mn 0.0097 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0194] Comparative Example 1 Ni 0.87 Co 0.05 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.05. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0195] The mixture was calcined at 780°C for 5 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8635 Co 0.0496 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in the form of secondary particles in which primary particles are aggregated was produced. Next, 100 parts by weight of the produced lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed with water using a filter press. The washed product was dried at 130°C for 4 hours to produce a dried product.

[0196] To the dried product manufactured above, H3BO3 was added at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide and mixed to produce a mixture. The mixture was heat-treated at 300°C for 5 hours in an air atmosphere to obtain a coated product. The coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8558 Co 0.0492 Mn 0.0787 Al 0.0049 Y 0.0010 Zr 0.0015 B 0.0089 It was O2.

[0197] Comparative Example 2 Ni 0.87 Co 0.05 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50A mixture of lithium (Li) (12.2 μm) and LiOH was prepared such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. Al(OH)3 was added to this mixture at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0198] The mixture was calcined at 780°C for 5 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 11.8 μm, LiNi 0.8635 Co 0.0496 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in the form of secondary particles in which primary particles are aggregated was produced. Next, 100 parts by weight of the produced lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed with water using a filter press. The washed product was dried at 130°C for 4 hours to produce a dried product.

[0199] To the dried product manufactured above, H3BO3 was added at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide and mixed to produce a mixture. The mixture was heat-treated at 300°C for 5 hours in an air atmosphere to obtain a coated product. The coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 12.2 μm, and a positive electrode active material was produced in which a coating portion containing B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8558 Co 0.0492 Mn 0.0787 Al 0.0049 Y 0.0010 Zr 0.0015 B 0.0089 It was O2.

[0200] Comparative Example 3 Ni0.94 Co 0.05 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (14.5 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.02. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0201] The mixture was calcined at 730°C for 5 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 14.2 μm, LiNi 0.9330 Co 0.0496 Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in the form of secondary particles formed by the aggregation of primary particles was produced. Next, 100 parts by weight of the produced lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed with water using a filter press. The washed product was dried at 130°C for 4 hours to produce a dried product.

[0202] To the dried product manufactured above, H3BO3 was added at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide and mixed to produce a mixture. The mixture was heat-treated at 300°C for 5 hours in an air atmosphere to obtain a coated product. The coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 14.2 μm, and a positive electrode active material was produced in which a coating portion containing B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9246 Co 0.0492 Mn 0.0098 Al 0.0050 Y 0.0010 Zr 0.0015 B 0.0089 It was O2.

[0203] Comparative Example 4 Ni 0.94 Co 0.05 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.02. Al(OH)3 was added to this mixture at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0204] The mixture was calcined at 730°C for 5 hours under an oxygen atmosphere to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.9330 Co 0.0496 Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in the form of secondary particles formed by the aggregation of primary particles was produced. Next, 100 parts by weight of the produced lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed with water using a filter press. The washed product was dried at 130°C for 4 hours to produce a dried product.

[0205] To the dried product manufactured above, H3BO3 was added at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide and mixed to produce a mixture. The mixture was heat-treated at 300°C for 5 hours in an air atmosphere to obtain a coated product. The coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 10.2 μm, and a positive electrode active material was produced in which a coating portion containing B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.9246 Co 0.0492 Mn 0.0098 Al0.0050 Y 0.0010 Zr 0.0015 B 0.0089 It was O2.

[0206] Comparative Example 5 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.04. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0207] The mixture was calcined in an oxygen atmosphere at 820°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0208] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50The particles were ground to a size of 9.8 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Y 0.0010 Zr 0.0015 It was O2.

[0209] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 9.8 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0210] Comparative Example 6 Ni 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture of lithium (Li) and LiOH (10.2 μm) was prepared by mixing lithium (Li) with the transition metal (Ni+Co+Mn) in a molar ratio (Li / (Ni+Co+Mn)) of 1.04. Al(OH)3 was added at concentrations of 1,470 ppm, Y2O3 at 1,000 ppm, and ZrO2 at 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and the mixture was prepared by mixing.

[0211] The mixture was calcined in an oxygen atmosphere at 920°C for 6 hours, and then at 800°C for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to obtain an average particle size (D 50 ) is 9.8 μm, LiNi 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 A lithium transition metal oxide having a composition represented by O2 and in a secondary particle form in which primary particles are aggregated was produced.

[0212] A mixture was prepared by adding Al(OH)3 to the lithium transition metal oxide in secondary particle form produced above, and Co(OH)2 so that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and Al(OH)3 at a content of 500 ppm relative to the total weight of the lithium transition metal oxide in secondary particle form produced above, and then mixing them uniformly. The mixture was heat-treated in an oxygen atmosphere at 740°C for 3 hours, and then at 500°C for 3 hours to obtain a first coated product. The first coated product was heated at room temperature to obtain an average particle size (D 50 The particles were ground to a size of 9.8 μm, and a positive electrode active material was produced in which a coating portion containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Y 0.0010 Zr 0.0015 It was O2.

[0213] To the pulverized first coated product, H3BO3 was added at a content of 500 ppm relative to the total weight of the pulverized first coated product and mixed to produce a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coated product. The second coated product was then heated at room temperature to obtain an average particle size (D 50The particles were ground to a size of 9.8 μm, and a positive electrode active material was produced in which a coating portion containing Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles formed by the aggregation of primary particles. The overall composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Y 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0214] Experimental example Experimental Example 1: Particle Analysis 1 The positive electrode active materials produced in Examples 1-11 and Comparative Examples 1-6 were each photographed using a scanning electron microscope (FEI quanta 250 FEG). The SEM images of Examples 1-11 are shown sequentially in Figures 1-11(A), and the SEM images of Comparative Examples 1-4 and Comparative Example 6 are shown sequentially in Figures 12-16(A). From the above SEM images, the average particle size of the primary particles present in each example and comparative example was measured and is shown in Table 1 below.

[0215] Then, the positive electrode active materials produced in Examples 1 to 11 and Comparative Examples 1 to 6 were ion-milled and photographed using a scanning electron microscope. The SEM images of Examples 1 to 11 are shown sequentially in Figures 1 to 11(B), and the SEM images of Comparative Examples 1 to 4 are shown sequentially in Figures 12 to 15(B). In Figures 1 to 15(B), the white rectangles are observed from the SEM images of the cross-section of secondary particles taken relative to the cross-section of the positive electrode active material, and represent the size of the cross-section of the secondary particles relative to the average particle size (D 50 The SEM images of the cross-sections of secondary particles having a size within the range shown are presented with a unit area of ​​5 μm x 5 μm set within the cross-section of the secondary particle, and the number of primary particle cross-sections confirmed within this unit area is shown in Table 1 below.

[0216] Furthermore, an image analysis based on an artificial intelligence model was performed on the SEM image of Example 1 of the present invention, and the segmentation image showing multiple lithium composite transition metal oxides is shown in Figure 17, while the segmentation image of Comparative Example 2 is shown in Figure 18.

[0217] [Table 1]

[0218] Experimental Example 2: Particle Analysis 2 The positive electrode active materials produced in Examples 1, 2, and 8 were ion-milled and then imaged using a transmission electron microscope (FEI Titan cubed G2 60-300). TEM images of the cross-sections of the primary particles of the positive electrode active materials in Examples 1, 2, and 8 are shown in Figures 19 to 21, respectively.

[0219] Referring to Figures 1 to 11 and Table 1, it can be confirmed that in the case of the positive electrode active materials of Examples 1 to 11, the material contains secondary particles formed by the aggregation of multiple primary particles, and that the average particle size of these multiple primary particles, as measured from SEM images, is between 1.5 μm and 5.0 μm. Furthermore, it can be confirmed that these multiple primary particles include three or more disk-shaped primary particles. Here, disk-shaped primary particles refer to primary particles observed from SEM images of the surface or cross-section of the secondary particles, where, when a virtual tangent line with the most points of contact is drawn to two boundary lines of primary particles existing within an angle of 45° or less relative to the long axis, and a virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle is between 150° and 210°. For reference, in Figures 1 to 11 (B), when a hypothetical yellow tangent line with the most points of contact is drawn to two boundary lines of primary particles existing within an angle of 45° or less, using the red major axis direction as a reference, the one hypothetical line (not shown) that crosses the two yellow tangent lines satisfies the condition that the ipsilateral interior angle is between 150° and 210°. Primary particles that fall into this category are defined as disc-shaped primary particles. Furthermore, it can be confirmed that the minor axis of these disc-shaped primary particles is 0.3 μm or more, and the aspect ratio (major axis / minor axis) is 1.5 or more. It can also be confirmed that the number of primary particle cross-sections per unit area is between 1 and 100. Specifically, it can be confirmed that the number of primary particle cross-sections per unit area is between 8 and 24.

[0220] Furthermore, referring to Figures 1 to 11 and Figures 19 to 21, it can be confirmed that in the case of the positive electrode active material according to one embodiment of the present invention, the area ratio of the (003) plane among the crystal planes on the surface of the primary particles is maximized.

[0221] On the other hand, in the case of the positive electrode active materials of Comparative Examples 1 to 4, it can be confirmed from the SEM images that the average particle size of the primary particles is small, less than 500 nm.

[0222] Furthermore, referring to Figures 17 and 18, it can be confirmed that the positive electrode active material according to one embodiment of the present invention contains single-crystal primary particles.

[0223] Experimental Example 3: Particle Analysis 3 The positive electrode active materials produced in Examples 1-11 and Comparative Examples 1-6 were each imaged using a scanning electron microscope (FEI quanta 250 FEG) equipped with EBSD.

[0224] Of these, the size of the secondary particle cross-section observed from the electron backscatter diffraction (EBSD) patterns of SEM images of the cross-sections of secondary particles taken from the cross-sections of the positive electrode active materials of Examples 1-4, 8, 10 and 11, and Comparative Example 3 (measured under the conditions of acceleration voltage 20kV, WD 16mm, measurement magnification 5,000x (width 16μm × height 16μm), step size 0.025μm) is the average particle size (D) of the secondary particles. 50 For the EBSD patterns of the cross-sections of secondary particles having a size within the specified range, a unit area of ​​5 μm x 5 μm was set in the central region and the outer region within the cross-section of the secondary particle, respectively, as shown in Figures 22 (Example 1), 23 (Example 2), 24 (Example 3), 25 (Example 4), 26 (Example 8), 27 (Example 10), 28 (Example 11), and 29 (Comparative Example 3). The number of grain cross-sections observed within this unit area and the degree of single crystallinity were calculated using the following formula 1, and are shown together in Table 2 below.

[0225]

number

[0226] [Table 2]

[0227] Referring to Table 2, it can be confirmed that in the case of the positive electrode active materials of Examples 1 to 11, the number of grain cross-sections per unit area is between 1 and 150. Specifically, it can be confirmed that the number of grain cross-sections per unit area is between 3 and 19. Furthermore, the degree of single crystallinity is 0.15 μm. 3 It can be confirmed that the above is true. Specifically, the degree of single crystallinity is 0.86 μm. 3 or more, 1.57μm 3 It can be confirmed that the following is true.

[0228] Experimental Example 4: Particle Analysis 4 From the SEM image of the positive electrode active material obtained in Experimental Example 1, the degree of single-particle formation (Dv) corresponds to the diameter of the volume at the point where 50% of the volume cumulative distribution of primary particles present in each example and comparative example is reached. 50 The following measurements were taken and are shown in Table 3 below.

[0229] Specifically, the area of ​​each primary particle is measured by the number of pixels corresponding to each of the n primary particles observed from the image projected onto a two-dimensional plane from SEM images of the surface of secondary particles taken on the surface of the positive electrode active material in Examples 1-11 and Comparative Examples 1-6. Then, assuming that the surface of the primary particle is circular, the radius of the surface of the primary particle is derived using the radius of a circle having the same area as the surface area of ​​each primary particle. Using the radius, the value of volume is calculated using the following equation 5, and the degree of single-particle formation (Dv) corresponding to the diameter of the volume at the point where the cumulative volume distribution of the primary particles reaches 50% is calculated. 50 The calculations were performed and are shown in Table 3 below.

[0230]

number

[0231] [Table 3]

[0232] Referring to Table 3, it can be confirmed that in the case of the positive electrode active materials of Examples 1 to 11, the degree of single particle formation is 1.2 μm or more and 3.8 μm or less. Specifically, it can be confirmed that the degree of single particle formation is 1.65 μm or more and 3.55 μm or less.

[0233] On the other hand, in the case of the positive electrode active materials of Comparative Examples 1 to 6, it can be confirmed that the degree of single particle formation is either less than 1.2 μm or greater than 3.8 μm.

[0234] Experimental Example 5: Particle Analysis 5 Electron spectroscopy (ESCA) was performed on the cathode active materials produced in Examples 1-11 and Comparative Examples 1-6 using a Thermo Fisher K-alpha XPS instrument to analyze the elemental distribution of the Co and B coating layers present on the surface. For depth profiling, etching was performed at a rate of 0.3 nm / 10 s using an Ar ion source, and the atomic %) content of B and Co in the coating layers with thicknesses from 0 to 100 nm was measured. The results are shown in Table 4 (B coating layer) and Table 5 (Co coating layer), respectively.

[0235] EPMA cross-sectional analysis was performed on the positive electrode active material of Example 1 to confirm its surface coating properties. First, the positive electrode active material of Example 1, carbon black conductive material, and PVDF binder were mixed in N-methylpyrrolidone (NMP) solvent in a weight ratio of 95:2:3 to produce a positive electrode slurry. The produced positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to an electrode porosity of 20% to produce a positive electrode. To obtain a flat surface for EPMA cross-sectional analysis, the positive electrode was subjected to Ar-ion milling using a HITACHI IM-5000 instrument at an acceleration voltage of 6kV to obtain a cross-section of the positive electrode sample. Then, using a JEOL JXA-iHP200F instrument, a cross-sectional image of the positive electrode sample was observed at an acceleration voltage of 15kV and a probe current of 50nA, and is shown in Figure 30.

[0236] [Table 4]

[0237] [Table 5]

[0238] Referring to the SEM images in Figures 1 to 11 and Tables 4, 5, and Figure 30, it can be confirmed that in the case of the positive electrode active materials of Examples 1 to 11, a coating portion containing Co and / or B is formed on the surface of the primary particles, the interface of the primary particles, and / or the surface of the secondary particles. Furthermore, it can be confirmed that the coating portion has both island-like forms formed on the surface of the primary particles, the interface of the primary particles, and / or a portion of the surface of the secondary particles, and forms of a coating layer that surrounds the surface of the primary particles, the interface of the primary particles, and / or the surface of the secondary particles.

[0239] Experimental Example 6: Volume Cumulative Distribution Analysis For the positive electrode active materials produced in Examples 1-11 and Comparative Examples 1-6, a particle size analyzer (PSD, Malvern, martersizer 3500) was used to determine the D min , D 50 and D max , the mode in the volume cumulative distribution by particle size, and the y-value P of the peak point at the uppermost end of the y-axis of the peak indicated by the mode in the volume cumulative distribution. MODE , θ L and θ R Measure θ L -θ R The calculations were performed and are shown in Table 6.

[0240] Then, the skewness value S is calculated using equation 3 below, and the y value P is the peak point at the uppermost end of the y axis of the peak shown by the mode of the volume cumulative distribution. MODE The ratio of the skewness value S to the ratio S / P MODE The calculations were performed and are shown together in Table 6 below.

[0241]

number

[0242] Furthermore, the cumulative volume distributions of the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 and 3, measured using a laser diffraction particle size analyzer, are shown in frequency distribution graphs in Figures 31 (Example 1), 32 (Example 2), 33 (Example 3), 34 (Example 4), 35 (Example 5), 36 (Example 6), 37 (Example 7), 38 (Example 8), 39 (Example 9), 40 (Example 10), 41 (Example 11), 42 (Comparative Example 1), and 43 (Comparative Example 3), respectively. These graphs show the volume cumulative distributions measured using a laser diffraction particle size analyzer for Examples 1 to 11 and Comparative Examples 1 and 3.

[0243] Then, the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 and 3 is shown in frequency distribution graphs in Figures 44 (Example 1), 45 (Example 2), 46 (Example 3), 47 (Example 4), 48 (Example 5), 49 (Example 6), 50 (Example 7), 51 (Example 8), 52 (Example 9), 53 (Example 10), 54 (Example 11), 55 (Comparative Example 1), and 56 (Comparative Example 3), respectively. These graphs show the volume cumulative distribution measured using a laser diffraction particle size analyzer for Examples 1 to 11 and Comparative Examples 1 and 3.

[0244] [Table 6]

[0245] Referring to Table 6, in the case of the positive electrode active materials of Examples 1 to 11, the above D 50 It can be confirmed that the size is between 7.0 μm and 20.0 μm. Also, (θ L -θ RIt can be confirmed that the value of ) is between 6 and 20. Furthermore, the volume cumulative distribution measured using a laser diffraction particle size analyzer can be shown in a frequency distribution graph where the x-axis represents the particle diameter as the x-value increases from left to right on a linear scale, and the y-axis represents the weight distribution as the y-value increases from bottom to top, confirming that it exhibits positive skewness.

[0246] Experimental Example 7: Measurement of Rolling Density Using an automatic pellet press (Carver, 3887.4), zero-point adjustment for thickness was performed on a circular pellet holder with a diameter of 13 mm using a cylindrical mold. Next, 3 g each of the positive electrode active material produced in Examples 1-11 and Comparative Examples 1-6 was placed in the circular pellet holder, and the thickness of the formed pellets was measured by applying force until a force equivalent to 9,000 kgf was reached. Then, the volume of the pellets was calculated using Equation 4 below, and the rolling density was calculated using Equation 2 below, as shown in Table 7 below.

[0247] [Formula 4] Pellet volume (cm³) 3 ) = π (radius of the circular pellet holder) 2 × Pellet thickness

[0248] [Formula 2] Rolling density (g / cm³) 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm³) 3 )

[0249] [Table 7]

[0250] Referring to Table 7, for the positive electrode active materials of Examples 1 to 11, the rolling density is 3.60 g / cm³. 3 It can be confirmed that the above is true. Specifically, the rolling density is 3.66 g / cm³. 3 This confirms that the above is true.

[0251] Experimental Example 8: BET Specific Surface Area Measurement The specific surface area was measured by the adsorption and desorption of nitrogen gas. Specifically, after measuring the weight of an empty cell, 3 g each of the positive electrode active material produced in Examples 1-11 and Comparative Examples 1-6 was taken and pretreated at 130°C for 3 hours. After measuring the weight of the cell after the pretreatment process, a Dewar flask containing liquid nitrogen was prepared, and the cell was sealed. Under a nitrogen atmosphere, the BET specific surface area was measured from the amount of nitrogen gas adsorbed using a gas adsorption analyzer (Micromeritics TriStarr II), and is shown in Table 8 below.

[0252] [Table 8]

[0253] Referring to Table 8, for the positive electrode active materials of Examples 1 to 11, the BET specific surface area is 0.20 m². 2 / g or more, 0.35m 2 It can be confirmed that it is less than / g. Specifically, the BET specific surface area is 0.240m². 2 / g or more, 0.338m 2 It can be confirmed that the amount is less than / g.

[0254] Experimental Example 9: Manufacturing and charge / discharge evaluation of coin-type half-cells 95 parts by weight of each positive electrode active material produced in Examples 1-11 and Comparative Examples 1-6, 2 parts by weight of conductive material (Denka, FX35), and 3 parts by weight of binder (KUREHA, KF9709) were mixed in an N-methylpyrrolidone (NMP) solvent to produce a positive electrode slurry. The produced positive electrode slurry was applied to one surface of a 20 μm thick aluminum current collector, and the cathode was manufactured by rolling it so that the porosity of the positive electrode active material layer was 24 volume%.

[0255] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode, with a porous polyethylene separator interposed between the positive and negative electrodes. This assembly was placed inside a battery case, and an electrolyte was injected to manufacture a lithium secondary battery. The electrolyte was prepared by dissolving 1M LiPF6 in an organic solvent mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a volume ratio of 3:3:4.

[0256] Using lithium secondary batteries containing the positive electrode active materials of Examples 1-11 and Comparative Examples 1-6 manufactured above, charging was performed in CC / CV mode at 25°C with a constant current of 0.1C up to 4.25V (end current 0.05C), and then discharging was performed in CC mode until the voltage reached 2.5V. The charging and discharging capacities were measured and are shown in Table 9 below. Here, 1C = 200mA / g was set.

[0257] Furthermore, the manufactured lithium secondary battery was charged at 45°C with a constant current of 0.5C in CC / CV mode up to 4.25V (termination current 0.05C), and then discharged in CC mode with a constant current of 1.0C until it reached 2.5V. This process was considered one cycle, and 50 cycles were repeated. The capacity retention rate was defined as the percentage of the discharge capacity of the 50th cycle relative to the discharge capacity of the first cycle, and is shown in Table 9 below.

[0258] [Table 9]

[0259] Experimental Example 10: Evaluation of High-Rate Discharge Capacity Using the lithium secondary battery manufactured in Experimental Example 9, charging was performed in CC / CV mode at 25°C with a constant current of 0.5C to 4.25V (end current 0.05C), and then the discharge capacity was measured while discharging in CC mode at a constant current of 0.1C to 2.5V. Similarly, charging was performed in CC / CV mode at 25°C with a constant current of 0.5C to 4.25V (end current 0.05C), and then the discharge capacity was measured while discharging in CC mode at a constant current of 1.0C to 2.5V. The percentage of the discharge capacity after charging at 0.5C and discharging at 0.1C is shown in Table 10 below.

[0260] [Table 10]

[0261] Referring to Tables 9 and 10, it can be confirmed that the batteries containing the positive electrode active materials of Examples 1 to 11 have a large discharge capacity, high efficiency and high-temperature capacity retention rate, low DC resistance, and excellent rate characteristics. In contrast, the batteries containing the positive electrode active materials of Comparative Examples 1 to 6 have problems with poor efficiency and high-temperature capacity retention rate, and the batteries containing the positive electrode active materials of Comparative Examples 1 to 5 have problems with poor rate characteristics.

[0262] These results confirm that the positive electrode active material of the present invention is a positive electrode active material that can simultaneously solve the problems of both secondary particles and single particles in conventional high-nickel (High Ni) positive electrode active materials. By realizing a positive electrode active material in the form of secondary particles with primary particle size at the micron level, it is possible to improve energy density not only by improving cell characteristics such as the lifespan of lithium secondary batteries and reducing gas generation, but also by having excellent density characteristics.

Claims

1. It contains secondary particles formed by the aggregation of multiple primary particles. The aforementioned plurality of primary particles have an average particle size of 1.5 μm or more and 5.0 μm or less, as measured from SEM images. The particle size of the primary particle is the particle size based on the major axis of the primary particle. For each primary particle observed from the SEM image of the surface of the secondary particle (measurement magnification 3,000x), the volume value is calculated from equation 5 below, and the degree of single-particle formation (Dv) corresponds to the diameter of the volume at the point where the cumulative volume distribution of the primary particles reaches 50%. ５０ A positive electrode active material having a diameter of 1.2 μm or more and 3.8 μm or less. [Math 1] In the above formula 5, Radius is the radius of the surface of the primary particle, assuming that the surface of the primary particle is circular, as observed from the SEM image of the secondary particle's surface (measurement magnification 3,000x).

2. The degree of single-particle formation (Dv ５０ The positive electrode active material according to claim 1, wherein the diameter of the ) is 1.65 μm or more and 3.55 μm or less.

3. The positive electrode active material according to claim 1, comprising a lithium transition metal composite oxide containing nickel, cobalt, and manganese.

4. The positive electrode active material according to claim 1, comprising a lithium transition metal composite oxide containing 60 mol% or more nickel among the total transition metals.

5. The positive electrode active material according to claim 1, comprising a lithium transition metal composite oxide having an average composition represented by the following chemical formula 1. [Chemical formula 1] Li ｘ Ni ａ Co ｂ Mn ｃ M １ ｄ O ２ In the aforementioned chemical formula 1, M １ is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, S, and Y. 0.9 ≤ x ≤ 1.3, 0.6 ≤ a < 1.0, 0 < b < 0.4, 0 < c < 0.4, 0 ≤ d ≤ 0.2, and a + b + c + d = 1.

6. The positive electrode active material according to claim 1, wherein the plurality of primary particles include single-crystal primary particles.

7. The secondary particles are defined by the average particle size (D) based on the volume cumulative distribution measured using a laser diffraction particle size analyzer. ５０ The positive electrode active material according to claim 1, wherein the diameter is 7.0 μm or more and 20.0 μm or less.

8. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 7.

9. A lithium secondary battery comprising a positive electrode according to claim 8, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

Images