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

Abstract

The present invention relates to a positive electrode active material that can simultaneously solve the problems of both secondary particles and single particles in the conventional method. This positive electrode active material contains particles such as 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 density characteristics and improving energy density. The present invention also relates to a positive electrode containing this positive electrode active material and a lithium secondary battery.

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. 10-2024-0057118 dated April 29, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference. The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0002] In recent years, with the advancement of technologies such as electric vehicles, the demand for high-capacity secondary batteries has increased, and research on high-nickel (High Ni) cathode active materials with superior capacity characteristics is being actively conducted.

[0003] High-nickel positive electrode active materials, formed in a secondary particle structure where primary particles are aggregated, undergo structural degradation during charging and discharging of lithium secondary batteries. However, relatively speaking, changes in the lattice structure constant, i.e., changes in volume within the unit cell, occur more frequently. Such volume changes cause cracks in the positive electrode active material. Furthermore, cracks can also occur in the positive electrode active material due to pressure during electrode rolling.

[0004] The cracks that occur in the high-nickel cathode active material in this way worsen during the charging and discharging process of the lithium secondary battery. This can lead to the electrolyte being unable to contact the cracks, or the cracks acting as voids that reduce conductivity, thereby degrading the lifespan characteristics of the lithium secondary battery, or they can act as a factor that increases resistance.

[0005] 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 the problem of non-uniform particle size distribution, resulting in a large particle size distribution in the single-particle cathode active material obtained after grinding. Furthermore, single-particle cathode active materials have a small specific surface area and are weak in terms of cell resistance characteristics. Therefore, there is a need to develop cathode active materials that can simultaneously solve the problems of both secondary particles and single particles.

[0006] 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, by including primary particles with an average particle size at the micron level, can improve rolling density and minimize cracks caused by rolling, and the specific surface area can be improved by the secondary particle structure, thereby improving cell properties.

[0007] 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 compared to 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 deteriorates to a rock salt structure, causing a decrease in crystallinity, which in turn degrades the performance of the positive electrode active material. In particular, the deterioration of the layered structure of the lithium transition metal composite oxide to a rock salt structure at high heat treatment temperatures becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the positive electrode active material is high, as nickel is the most vulnerable component. 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]

[0008] [Patent Document 1] Korean Registered Patent Publication No. 10-1785262 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] 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.

[0010] In other words, the present invention has been made to solve the problems of the above-mentioned prior art, and aims to provide a positive electrode active material that has a high nickel content among the transition metals of lithium transition metal composite oxide, has excellent capacity characteristics, and is a positive electrode active material in the form of secondary particles with primary particle size at the micron level, thereby providing not only cell characteristics such as improved lifespan and reduced gas generation, but also excellent density characteristics and improved energy density. Furthermore, the present invention aims to provide a positive electrode containing the positive electrode active material and a lithium secondary battery. [Means for solving the problem]

[0011] 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. (1) The present invention includes secondary particles formed by the aggregation of a plurality of primary particles, wherein the 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, and the particle size of the primary particles is the particle size based on the major axis of the primary particles, and the materials are aluminum (Al), zirconium (Zr), and M 3 The lithium transition metal composite oxide includes the M 3 The present invention provides a positive electrode active material that includes a coating portion containing a metallic element with an oxidation state of +4 or higher, and containing cobalt (Co) and boron (B).

[0012] (2) In the present invention, the M 3 The present invention provides a positive electrode active material as described in (1), which is one or more selected from the group consisting of titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo), and niobium (Nb).

[0013] (3) In the present invention, Al is contained in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal composite oxide, Zr is contained in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal composite oxide, and M 3It provides the positive electrode active material according to (1) or (2) above, which is contained in a content of 100 ppm to 2,000 ppm with respect to the total weight of the lithium transition metal composite oxide.

[0014] (4) The present invention provides the positive electrode active material according to any one of (1) to (3) above, which contains a lithium transition metal composite oxide containing nickel, cobalt, and manganese.

[0015] (5) The present invention provides the positive electrode active material according to any one of (1) to (4) above, which contains a lithium transition metal composite oxide containing 60 mol% or more of nickel among all transition metals.

[0016] (6) The present invention provides the positive electrode active material according to any one of (1) to (5) above, which contains a lithium transition metal composite oxide having an average composition represented by the following Chemical Formula 1.

[0017] [Chemical Formula 1] Li x Ni a Co b Mn c M 1 d O2

[0018] 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.

[0019] (7) In the present invention, it provides the positive electrode active material according to any one of (1) to (6) above, wherein the plurality of primary particles include single crystal primary particles.

[0020] (8) In the present invention, the secondary particles have an average particle diameter (D 50The present invention provides a positive electrode active material according to any one of the above items (1) to (7), wherein the diameter of the ) is 7.0 μm or more and 20.0 μm or less.

[0021] (9) The present invention provides a positive electrode comprising a positive electrode active material described in any one of the above (1) to (8).

[0022] (10) The present invention provides a lithium secondary battery comprising the positive electrode, the negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte as described in (9) above. [Effects of the Invention]

[0023] 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 primary particle size at the micron level, it is possible to improve not only cell characteristics such as the lifespan of lithium secondary batteries and the amount of gas generated, but also density characteristics and energy density. [Brief explanation of the drawing]

[0024] [Figure 1] This is an SEM image of a cross-section of the positive electrode active material in Example 1. [Figure 2] This is an SEM image of a 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 a cross-section of the positive electrode active material in Comparative Example 1. [Figure 4] (A) SEM image of the positive electrode active material and (B) SEM image of a cross-section of the positive electrode active material in Comparative Example 2. [Figure 5] (A) SEM image of the positive electrode active material, and (B) SEM image of a cross-section of the positive electrode active material in Comparative Example 3. [Figure 6] 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 7] (A) SEM image of the positive electrode active material and (B) SEM image of a cross-section of the positive electrode active material in Comparative Example 5. [Figure 8] (A) SEM image of the positive electrode active material and (B) SEM image of a cross-section of the positive electrode active material in Comparative Example 6. [Figure 9] This is a segmentation image showing multiple lithium composite transition metal oxides segmented by image analysis based on an artificial intelligence model from an SEM image of the positive electrode active material of Example 1. [Figure 10] This is a segmentation image showing multiple lithium composite transition metal oxides segmented by image analysis based on an artificial intelligence model performed on the SEM image of the positive electrode active material of Example 2. [Figure 11] This is a segmentation image showing multiple lithium composite transition metal oxides, obtained by performing image analysis based on an artificial intelligence model from an SEM image of the positive electrode active material of Comparative Example 1. [Figure 12] This is a segmentation image showing multiple lithium composite transition metal oxides segmented by image analysis based on an artificial intelligence model performed on the SEM image of the positive electrode active material of Comparative Example 2. [Figure 13] This is an EBSD pattern image of the cross-section of the positive electrode active material of Comparative Example 4. [Figure 14] This is an EPMA analysis image of the positive electrode active material of Example 1. [Figure 15] This is an EPMA analysis image of the positive electrode active material in Example 2. [Modes for carrying out the invention]

[0025] The present invention will be described in more detail below to facilitate understanding of it. 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 appropriately define the concepts of terms in order to best describe their invention.

[0026] 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 consists of a single crystal or multiple crystal grains.

[0027] 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.

[0028] In this invention, the term "average particle size (D 50 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 volume cumulative distribution by particle size in the measuring device reaches 50%. 50 It can be measured.

[0029] 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.

[0030] 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.

[0031] positive electrode active material The present invention provides a positive electrode active material. According to one embodiment of the present invention, the material includes secondary particles formed by the aggregation of a plurality of primary particles, wherein 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.

[0032] 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 be a secondary particle formed by the aggregation of at least two, and more specifically, at least three or more primary particles.

[0033] According to one embodiment of the present invention, the plurality of primary particles may have an average particle size measured from SEM images 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 sizes 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, 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. If it is 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.

[0034] 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 among all transition metals. 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.

[0035] 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.

[0036] [Chemical formula 1] Li x Ni a Co b Mn c M 1 d O2

[0037] 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。

[0038] 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, and may also be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0039] According to one embodiment of the present invention, in the chemical formula 1, a, b, c, and d are each a transition metal, and are nickel (Ni), cobalt (Co), manganese (Mn), and doping element (M 1) may be the mole fraction of ). For example, a above 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 above 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. 1 ) is a mole fraction that is 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 value 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.

[0040] According to one embodiment of the present invention, the plurality of primary particles may include single-crystal primary particles. In this 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.

[0041] 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. Specifically, the secondary particle may have an average particle size (D 50 ) 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, Or 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 , 18.4 μm or less, 18.3 μm or less, 18.2 μm or less, 18.1 μm or less, 18.0 μm or less, 17.9 μm or less, 17.8 μm or less, 17.7 μm or less, 17.6 μm or less , 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. If it is within this range, the rolling density of the positive electrode active material can be further improved, and the lifespan can be further improved.

[0042] 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 metals, and the multiple primary particles are formed by the aggregation of multiple primary particles with a particle size of 0.5 μm to 5.0 μm, specifically micron-level primary particles of 1.0 μm or more, and more specifically, multiple primary particles with an average particle size of 2.0 μm to 3.5 μm, as measured from SEM images, with an average particle size (D 50 ) may contain secondary particles with a particle size of 7.0 μm or more and 20.0 μm or less, and can be described 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.

[0043] As described above in the background technology of the present invention, in order to manufacture a cathode 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 compared to secondary particles with primary particle sizes at the submicron level (less than 1 μm). However, the higher the heat treatment temperature, the more the layered structure of the lithium transition metal composite oxide deteriorates to a rock salt structure, causing a decrease in crystallinity, which degrades the performance of the cathode active material. In particular, the deterioration of the layered structure of the lithium transition metal composite oxide to a rock salt structure at high heat treatment temperatures becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the cathode active material is high, as nickel is the most fragile component. Therefore, conventionally, cathode active materials in the form of secondary particles with primary particle sizes at the micron level could only be applied to mid-nickel cathode active materials in which the nickel content among the transition metals of the lithium transition metal composite oxide was at the 50 mol level. It was not possible to manufacture cathode active materials in the form of secondary particles with primary particle sizes at the micron level for high-nickel cathode active materials, which have a high nickel content among the transition metals of the lithium transition metal composite oxide and excellent capacitance characteristics.

[0044] However, the positive electrode active material of the present invention has a high nickel content among the transition metals in the lithium transition metal composite oxide, and even if the layered structure of the lithium transition metal composite oxide deteriorates to a rock salt structure at high heat treatment temperatures, it recovers the rock salt structure back to a layered structure, thereby solving the aforementioned problems. Specifically, unlike conventional mid-nickel positive electrode active materials, the positive electrode active material of the present invention 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 metals, and it contains secondary particles with a primary particle size at the micron level, and recovers the rock salt structure formed by high heat treatment temperatures back to a layered structure, thereby exhibiting excellent crystallinity of the lithium transition metal composite oxide and simultaneously solving the problems of both secondary particles and single particles in the conventional invention. The positive electrode active material of the present invention can be manufactured by restoring the rock salt structure formed by high heat treatment temperatures as described above to a layered structure. The method for restoring the rock salt structure to a layered structure is not limited, but according to one embodiment of the present invention, the method for restoring the rock salt structure to a layered structure may be to apply a cobalt (Co) coating to a lithium transition metal composite oxide containing a rock salt structure formed by high heat treatment temperatures.

[0045] According to one embodiment of the present invention, the plurality of primary particles may include disk-shaped primary particles, and specifically, may include three or more disk-shaped primary particles. In this case, the cell lifetime and energy density are excellent.

[0046] According to one embodiment of the present invention, the disc-shaped primary particle may mean a primary particle observed from an SEM image of the surface or cross-section of a secondary particle, in which, when two boundary lines of a primary particle located within an angle of 45° or less with respect to the major axis direction are each drawn with respect to the most numerous tangent lines, and one virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle is 150° or more and 210° or less, the minor axis of the primary particle is 0.3 μm or more, and the aspect ratio (major axis / minor axis) is 1.5 or more. Specifically, the disc-shaped primary particle may have a minor axis of 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, if the minor axis of the disc-shaped primary particle is 0.3 μm or more and the aspect ratio (major axis / minor axis) is 1.5 or more, the area ratio of the (003) plane among the crystal planes on the surface of the primary particle can be the largest.

[0047] According to one embodiment of the present invention, the disc-shaped primary particle may mean a primary particle observed from an SEM image of the surface or cross-section of a secondary particle, in which, when two boundary lines of a primary particle located within an angle of 45° or less with respect to the major axis direction are each drawn with the most contact points, and a single virtual line is drawn crossing the two tangents, the ipsilateral interior angle is 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 particle is the largest. Here, when the area ratio of the (003) plane among the crystal planes on the surface of the disc-shaped primary particle is the largest, the primary particle may have a minor axis of 0.3 μm or more and an aspect ratio (major axis / minor axis) of 1.5 or more. That is, the fact that the area ratio of the (003) plane among the crystal planes on the surface of the primary particle is the largest can be confirmed by the fact that the minor axis of the primary particle is 0.3 μm or more and the aspect ratio (major axis / minor axis) is 1.5 or more.

[0048] According to one embodiment of the present invention, the positive electrode active material is measured using a laser diffraction particle size analyzer, and in a frequency distribution graph where the x-axis shows the particle diameter as the x-value increases from left to right on a log scale, and the y-axis shows the weight distribution as the y-value increases from bottom to top, the peak point at the top of the y-axis of the peak appearing at the mode; and when a triangle is formed at the two points of tangency of the frequency distribution curve that are tangent at the full width at half maximum (FWHM) of the mode, the interior angle (θ) at the left point of tangency of the two points of tangency of the frequency distribution curve that are tangent at the FWHM is... L ) and the interior angle (θ) at the right-side point of tangency. R The difference (θ) L -θ R The angle (θ) 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 ) may be 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. The positive electrode active material has a ratio (θ) of the interior angle at the left contact point to the interior angle at the right contact point. L / θ R ) may be between 1.100 and 2.000. As a specific example, the ratio of the interior angle at the left tangency to the interior angle at the right tangency (θ L / θ R) 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 The above values ​​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 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.

[0049] 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.

[0050] According to one embodiment of the present invention, the positive electrode active material is the y-value (P) of the peak point at the top of the y-axis of the peak that appears in the mode of the volume cumulative distribution. MODE The ratio of the skewness value (S) to (S / P) MODE ) may be 0.037 or more and 0.150 or less. As a specific example, the positive electrode active material is the y value (P) of the peak point at the top of the y axis of the peak that appears in the mode of the volume cumulative distribution. MODE The ratio of the skewness value (S) to (S / P) MODE) are 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 Above, 0.055 or above, 0.056 or above, 0.057 or above, 0.058 or above, 0.059 or above, 0.060 or above, 0.061 or above, 0.062 or above, 0.063 or above, 0.064 or above, 0.065 or above, 0.066 or above, 0.067 or above, 0.068 or above, 0.069 or above, 0.070 or above, 0.071 or above, 0.07 It may be 2 or greater, 0.073 or greater, 0.074 or greater, 0.075 or greater, 0.076 or greater, 0.077 or greater, 0.078 or greater, 0.079 or greater, 0.080 or greater, 0.081 or greater, 0.082 or greater, 0.083 or greater, 0.084 or greater, 0.085 or greater, 0.086 or greater, 0.087 or greater, 0.088 or greater, 0.089 or greater, 0.090 or greater, 0.091 or greater, 0.092 or greater, 0.093 or greater, 0.094 or greater, 0.095 or greater, 0.096 or greater, 0.097 or greater, 0.098 or greater, 0.099 or greater, or 0.100 or greater, and may be 0.150 or less, 0.140 or less, 0.130 or less, 0.120 or less, or 0.110 or less. Here, the skewness value (S) may be calculated using the following formula 3.

[0051]

number

[0052] 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, 0.24m 2 / 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 or equal to / g. Within this range, DC resistance decreases and rolling density can be improved.

[0053] 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 is between 7.0 μm and 20.0 μm, and the size of the cross-section of the secondary particle observed from the SEM image of the cross-section of the secondary particle 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 within the cross-section of the secondary particle may be between 1 and 100.

[0054] 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 not only in the unit area but also in the unit area that contains at least a portion of the primary particle cross-section. 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 limited as long as it is within the cross-section of the secondary particle.

[0055] 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. 50For 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. Specifically, this 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, 25 or less, 20 or less, or 15 or less. If such a range is met, the positive electrode active material is formed by the aggregation of multiple primary particles, such as primary particles with a particle size of 0.5 μm to 5.0 μm, specifically micron-level primary particles of 1.0 μm or more, and more specifically, multiple primary particles with an average particle size of 2.0 μm to 3.5 μm, as measured from SEM images, with an average particle size (D 50 This indicates that the product contains secondary particles with a large particle size of 7.0 μm to 20.0 μm.

[0056] 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 between 7.0 μm and 20.0 μm, 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 between 7.0 μm and 20.0 μm. 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 between 1 and 150.

[0057] 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. 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 grain cross-sections that include not only all grain cross-sections observed within the unit area, but also all grain cross-sections that include at least a portion of the grain cross-section. 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 limited as long as it is within the cross-section of the secondary particle.

[0058] 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 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, this 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 formed by the aggregation of multiple primary particles, such as primary particles with a particle size of 0.5 μm to 5.0 μm, specifically micron-level primary particles of 1.0 μm or more, and more specifically, multiple primary particles with an average particle size of 2.0 μm to 3.5 μm, as measured from SEM images, with an average particle size (D 50 This indicates that the product contains secondary particles with a large particle size of 7.0 μm to 20.0 μm.

[0059] 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 all.

[0060]

number

[0061] 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 of 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), 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. 50 Of all grain cross-sections that can be observed from the cross-section of secondary particles having a size within the specified range, the area of ​​the grain cross-section is 0.196 μm².2 The radius of the cross-section of the grain when assuming that the cross-section of the grain is circular with respect to the cross-section of the above grain, and n is the number of grains.

[0062] 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 0.90 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.

[0063] According to one 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). Specifically, the positive electrode active material may contain aluminum (Al), yttrium (Y), and zirconium (Zr) as doping elements.

[0064] 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, and may also be present in a content of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0065] According to one embodiment of the present invention, the yttrium (Y) may be present in a content of 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal composite oxide. Specifically, the yttrium (Y) may be present 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, and may also be present 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.

[0066] According to one embodiment of the present invention, the zirconium (Zr) may be present in an amount of 500 ppm to 5,000 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, and may also be present in an amount 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.

[0067] 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.

[0068] [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

[0069] 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。

[0070] 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.

[0071] According to one embodiment of the present invention, in the chemical formula 2, a, b, c, d, e, f, and g are each a transition metal, such as nickel (Ni), cobalt (Co), manganese (Mn), and doping element (M 2), aluminum (Al), yttrium (Y), and zirconium (Zr) may be mole fractions. Specifically, a may be the mole fraction of nickel (Ni) among the transition metals, which 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, which 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, which 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 doping elements (Mn) among the transition metals. 2) is a mole fraction that is 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 aforementioned 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 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 be 0.0005 or less, or 0.0004 or less.

[0072] According to one embodiment of the present invention, in the chemical formula 2, y is the molar ratio of element A in which oxygen is substituted 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, and may also be 0.2 or less, 0.15 or less, or 0.1 or less.

[0073] 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 include aluminum (Al), zirconium (Zr), and M. 3 It may contain as a doping element.

[0074] 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).

[0075] 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, and may also be present in a content of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0076] 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, and may also be present in an amount of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0077] 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 3 It 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, and may also be included 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.

[0078] 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, wherein the coating portion may contain one or more coating elements selected from the group consisting of cobalt (Co) and boron (B).

[0079] As a specific example, the positive electrode active material includes secondary particles formed by the aggregation of multiple primary particles, and the multiple primary particles have an average particle size of 1.5 μm to 5.0 μm as measured from SEM images, and include aluminum (Al), zirconium (Zr), and metallic elements with an oxidation state of +4 or higher. 3 It may contain a lithium transition metal oxide and a coating portion containing cobalt (Co) and boron (B).

[0080] 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.

[0081] According to one embodiment of the present invention, the coating portion may be a coating layer formed surrounding at least one of the surfaces of primary particles, the interfaces of primary particles, and the surfaces of secondary particles.

[0082] 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).

[0083] 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 sequentially formed. According to one embodiment of the present invention, the coating portion may contain cobalt-boron oxide.

[0084] 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 a force equivalent to 9,000 kgf is applied to form pellets, the rolling density calculated by the following formula 2 is 3.60 g / cm³. 3 That's all.

[0085] [Formula 2] Rolling density (g / cm³) 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm³) 3 )

[0086] 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 The above is sufficient, 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 The above is sufficient, and there is no particular upper limit, but 10.0 g / cm³ is not. 3 The following is acceptable:

[0087] 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 92.0% 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 0.0C. 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.

[0088] 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 89.0% 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 0.0C. 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, but it may be 100% or less.

[0089] According to one embodiment of the present invention, when the volume value of the positive electrode active material is calculated for each primary particle observed from an SEM image (measurement magnification 3,000x) of the surface of the secondary particles using the following formula 5, the degree of single particle formation (Dv) corresponds to the volume diameter at the point where 50% of the cumulative volume distribution of the primary particles is reached. 50 The diameter may be between 1.2 μm and 3.8 μm.

[0090]

number

[0091] 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).

[0092] 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.

[0093] Method for manufacturing positive electrode active material This invention provides a method for producing a positive electrode active material. According to one embodiment of the present invention, the method for producing the positive electrode active material may be the method for producing the positive electrode active material described above.

[0094] 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 firing it to produce a fired product.

[0095] According to one embodiment of the present invention, step (S10) may be carried out by methods such as a method in which firing is performed by dividing the temperature interval within one firing step (one-step method), a method in which firing is performed by dividing the temperature interval within one firing step (two-step method), and a method in which pre-firing is performed before firing is performed by dividing the temperature interval within one firing step (pre-firing method).

[0096] According to one embodiment of the present invention, the one-step method is a method of performing firing in two consecutive temperature intervals within a single firing step, wherein the first stage of firing is performed on a mixture of positive electrode active material precursor and lithium raw material, and then the temperature interval is changed and a second stage of firing is performed. In this case, the second stage of firing may be performed at a lower temperature than the first stage of firing, and each firing temperature can be adjusted according to the nickel content, and the morphology and size of the primary particles and the average particle size of the secondary particles can be adjusted by such temperature adjustment.

[0097] According to one embodiment of the present invention, the two-step method is a method in which primary and secondary calcination are performed separately. Primary calcination is performed on a mixture of positive electrode active material precursor and lithium raw material, and after crushing the first calcined product produced by the primary calcination, secondary calcination is performed on the crushed product. In this case, the secondary calcination may be performed 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.

[0098] According to one embodiment of the present invention, the calcination method is a method of performing calcination prior to one-step calcination, and the calcination may be performed on a mixture of positive electrode active material precursor and lithium raw material, and the one-step method may be performed on the calcined product. In this case, the calcination may be performed at a lower temperature than that of the one-step calcination, and each calcination temperature can be adjusted according to the nickel content, and the morphology and size of the primary particles and the average particle size of the secondary particles can be adjusted by such temperature adjustment.

[0099] 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.

[0100] [Chemical formula 3] Ni a’ Co b’ Mn c’ (OH)2

[0101] 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。

[0102] According to one embodiment of the present invention, in the chemical formula 3, a', b', and c' may each be the mole fractions of nickel (Ni), cobalt (Co), and manganese (Mn) 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, 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.

[0103] According to one embodiment of the present invention, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a mixture thereof.

[0104] 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 be Al2O3, Al(OH)3, Al(NO3)3·9H2O, Al2(SO4)3, Y2O3, ZrO2, etc.

[0105] According to one embodiment of the present invention, the doping material may contain Al, Y, and Zr. Furthermore, the doping material may contain Al, Zr, and a metal element (M) with an oxidation state of +4 or higher. 3 ) may be included.

[0106] According to one embodiment of the present invention, in step (S10), when the positive electrode active material precursor and the lithium raw material are mixed, 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, and may also be 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 among the transition metals.

[0107] 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 include one or more coating raw materials selected from the group consisting of Co and B. Alternatively, step (S20) may further include an Al coating raw material.

[0108] 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 separately. As a specific example, the coating in step (S20) may include a step (S21) of mixing a Co coating raw material and an Al coating raw material with the positive electrode active material and heat-treating it, and a step (S22) of mixing a B coating raw material with the coated product produced in step (S21) and heat-treating it.

[0109] 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.

[0110] 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 can be carried out using any crushing apparatus capable of crushing the positive electrode active material without any particular limitations.

[0111] According to one embodiment of the present invention, the doping raw material and the coating raw material may 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 described above.

[0112] positive electrode The present invention provides a positive electrode containing the positive electrode active material. 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.

[0113] According to one embodiment of the present invention, the positive electrode current collector may contain a highly conductive metal and readily adhere to the positive electrode active material layer, but is not particularly limited as long as it is unreactive within the battery voltage range. As the positive electrode current collector, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treatment with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesion strength of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, mesh, porous body, foam, nonwoven fabric.

[0114] According to one embodiment of the present invention, the positive electrode active material layer may optionally contain a conductive material and a binder along with the positive electrode active material. In this case, the positive electrode active material may be present 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. When within this range, excellent capacitance characteristics can be observed.

[0115] According to one embodiment of the present invention, the conductive material is used to impart conductivity to the electrode and can be used in any battery without particular limitations as long as it has electronic conductivity without causing a chemical change. 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. One of these alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0116] 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, and one of these alone or a mixture of two or more may be used. The binder may be present in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0117] 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 described above 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 described above and, if necessary, 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.

[0118] 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 may be used. The amount of solvent used is sufficient to dissolve or disperse the cathode active material, conductive material, binder, and dispersant, and to have a viscosity that allows for excellent thickness uniformity when applied for cathode manufacturing, taking into account the coating thickness of the slurry and the manufacturing yield.

[0119] Lithium-ion rechargeable battery The present invention provides a lithium secondary battery including the positive electrode. 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 selectively 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.

[0120] 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. According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0121] 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. According to one embodiment of the present invention, the negative electrode active material may 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. β Examples include lithium-doped and dedoped metal oxides 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 one or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. In addition, either low-crystallinity carbon or high-crystallinity carbon may 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 may be present in an amount of 80% to 99% by weight based on the total weight of the anode active material layer.

[0122] According to one embodiment of the present invention, the binder in the negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and is usually added in an amount of 0.1% to 10% by weight based on 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.

[0123] 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 may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on 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 may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0124] According to one embodiment of the present invention, the negative electrode can be manufactured by coating a negative electrode active material and a negative electrode active material layer forming composition, which is manufactured by selectively dissolving or dispersing a binder and a conductive material in a solvent, onto a negative electrode current collector and then 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.

[0125] 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 the type of separator 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 may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and they may be selectively used as single-layer or multi-layer structures.

[0126] 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, a molten inorganic electrolyte, or any other such electrolyte that 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.

[0127] 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 hydrocarbon group with 2 to 20 carbon atoms in a linear, branched, or cyclic structure, which may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery (e.g., ethylene carbonate or propylene carbonate) and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0128] 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 lithium secondary batteries. 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 at least one selected from the group consisting of the following, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. 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 the above range, the electrolyte has suitable conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0129] 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 battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexalic acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0130] 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 portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, including hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0131] 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.

[0132] 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 can also be preferably used as a unit battery in medium- and large-sized battery modules containing multiple battery cells.

[0133] 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. 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.

[0134] The following describes in detail embodiments of the present invention so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0135] Examples and Comparative Examples Example 1 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.89 Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding 10.2 μm of lithium (Li) to LiOH such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.04. To this mixture, Al(OH)3 was added at concentrations of 1,470 ppm, TiO2 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 then prepared.

[0136] 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 0.0794 Al 0.0050 Ti 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.

[0137] A mixture was prepared by uniformly mixing the lithium transition metal oxide in secondary particle form produced above with Co(OH)2, so that the molar ratio of cobalt (Co) to the metal excluding 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. 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 total composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Ti 0.0010 Zr 0.0015 It was O2.

[0138] A mixture was prepared by adding H3BO3 at a content of 500 ppm relative to the total weight of the first coated product that had been crushed as described above, and mixing. 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 primary particles were crushed 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 total composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Ti 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0139] Example 2 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.89Co 0.03 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding 10.2 μm of lithium (Li) and LiOH to the transition metal (Ni+Co+Mn) such that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.04. To this, Al(OH)3 was added at concentrations of 1,470 ppm, Nb2O5 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 then prepared.

[0140] 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 0.0794 Al 0.0050 Nb 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.

[0141] A mixture was prepared by uniformly mixing the lithium transition metal oxide in secondary particle form produced above with Co(OH)2, so that the molar ratio of cobalt (Co) to the metal excluding 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. 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 total composition of the positive electrode active material including the coating portion was LiNi 0.8641 Co 0.0491 Mn 0.0777 Al 0.0066 Nb 0.0010Zr 0.0015 It was O2.

[0142] A mixture was prepared by adding H3BO3 at a content of 500 ppm relative to the total weight of the first coated product that had been crushed as described above, and mixing. 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 primary particles were crushed 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 total composition of the positive electrode active material including the coating portion was LiNi 0.8602 Co 0.0489 Mn 0.0773 Al 0.0066 Nb 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0143] Comparative Example 1 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.87 Co 0.05 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding and mixing lithium (Li) (10.2 μm) and LiOH such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. To this, 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.

[0144] 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 0.0015A lithium transition metal oxide having a composition represented by O2 and in the form of aggregated primary particles was produced. Next, 100 parts by weight of the lithium transition metal oxide in the form of secondary particles produced above 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.

[0145] A mixture was prepared by adding H3BO3 at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide to the dried product manufactured as described above and mixing. 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 total 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.

[0146] Comparative Example 2 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.87 Co 0.05 Mn 0.08 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding 12.2 μm of lithium (Li) to LiOH such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.05. To this mixture, 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 then prepared.

[0147] 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 0.8635Co 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 lithium transition metal oxide in the form of secondary particles produced above 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.

[0148] To the dried product produced above, H3BO3 was added and mixed at a content of 1,000 ppm based on the total weight of the lithium transition metal oxide to produce a mixture. The mixture was heat-treated at 300 °C for 5 hours in an air atmosphere to obtain a coated product. At room temperature, the coated product was ground so that the average particle size (D 50 ) became 12.2 μm, and a positive electrode active material in which a coating portion containing B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated was produced. The total 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 O2.

[0149] Comparative Example 3 In the form of secondary particles formed by aggregation of dozens to hundreds of primary particles, Ni 0.89 Co 0.03 Mn 0.08 (OH)2 having a composition represented by and a transition metal composite hydroxide (D 50 : 10.2 μm) and LiOH were mixed so that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) became 1.04. To this, Al(OH)3 was added and mixed at a content of 1,470 ppm and ZrO2 at a content of 1,500 ppm based on the total weight of the transition metal composite hydroxide to produce a mixture. ​​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 0.8643 Co 0.0497 Mn 0.0795 Al 0.0050 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.

[0151] A mixture was prepared by adding Al(OH)3 at a concentration of 500 ppm relative to the total weight of the lithium transition metal oxide produced above in secondary particle form, and Co(OH)2 such that the molar ratio of cobalt (Co) to the metal excluding lithium (Ni+Co+Mn+Al+Zr) (Co / (Ni+Co+Mn+Al+Zr)) was 0.02, 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 total composition of the positive electrode active material including the coating portion was LiNi 0.8455 Co 0.0686 Mn 0.0777 Al 0.0067 Zr 0.0015 It was O2.

[0152] A mixture was prepared by adding H3BO3 at a content of 500 ppm relative to the total weight of the first coated product that had been crushed as described above, and mixing. 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 primary particles were crushed 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 total composition of the positive electrode active material including the coating portion was LiNi 0.8380 Co 0.0680 Mn 0.0770 Al 0.0066 Zr 0.0015 B 0.0089 It was O2.

[0153] Comparative Example 4 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.94 Co 0.05 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding 14.5 μm of lithium (Li) to LiOH such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.02. To this mixture, 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 then prepared.

[0154] 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 aggregated primary particles was produced. Next, 100 parts by weight of the lithium transition metal oxide in the form of secondary particles produced above 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.

[0155] A mixture was prepared by adding H3BO3 at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide to the dried product manufactured as described above and mixing. 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 total 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.

[0156] Comparative Example 5 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.94 Co 0.05 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding and mixing lithium (Li) (10.2 μm) and LiOH such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.02. To this, 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.

[0157] 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 0.0015A lithium transition metal oxide having a composition represented by O2 and in the form of aggregated primary particles was produced. Next, 100 parts by weight of the lithium transition metal oxide in the form of secondary particles produced above 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.

[0158] A mixture was prepared by adding H3BO3 at a content of 1,000 ppm relative to the total weight of the lithium transition metal oxide to the dried product manufactured as described above and mixing. 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 total 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.

[0159] Comparative Example 6 Ni is a secondary particle form formed by the aggregation of tens to hundreds of primary particles. 0.94 Co 0.05 Mn 0.01 (D) transition metal composite hydroxide having a composition represented by (OH)2 50 A mixture was prepared by adding 14.5 μm of lithium (Li) to LiOH such that the molar ratio of lithium (Li) to the transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) was 1.04. To this mixture, Al(OH)3 was added at concentrations of 1,470 ppm, TiO2 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 then prepared.

[0160] 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 0.9330 Co 0.0496 Mn 0.0099 Al 0.0050 Ti 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.

[0161] A mixture was prepared by adding H3BO3 at a concentration of 500 ppm relative to the total weight of the lithium transition metal oxide to the lithium transition metal oxide produced as described above. The mixture was heat-treated at 330°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 9.8 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 total composition of the positive electrode active material including the coating portion was LiNi 0.9287 Co 0.0494 Mn 0.0099 Al 0.0050 Ti 0.0010 Zr 0.0015 B 0.0045 It was O2.

[0162] Experimental example Experimental Example 1: Particle Analysis 1 The positive electrode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 6 were each photographed using a scanning electron microscope (FEI, quanta250 FEG). The SEM images of Examples 1 and 2 are sequentially shown in Figures 1 and 2(A), respectively, and the SEM images of Comparative Examples 1 to 6 are sequentially shown in Figures 3 to 8(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.

[0163] Then, the positive electrode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 6 were ion-milled and photographed using a scanning electron microscope. The SEM images of Examples 1 and 2 are shown sequentially in Figures 1 and 2(B), respectively, and the SEM images of Comparative Examples 1 to 6 are shown sequentially in Figures 3 to 8(B). In Figures 1 to 8(B), the white squares 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 For SEM images of cross-sections of secondary particles having a size within the specified range, a unit area of ​​5 μm x 5 μm was set within the cross-section of the secondary particle, and the number of primary particle cross-sections observed within this unit area is shown in Table 1 below.

[0164] Furthermore, image analysis was performed on the SEM images of Examples 1 and 2 of the present invention based on an artificial intelligence model, and segmentation images showing multiple lithium composite transition metal oxides are shown in Figures 9 and 10, while segmentation images of Comparative Examples 1 and 2 are shown in Figures 11 and 12.

[0165] [Table 1]

[0166] Referring to FIGS. 1 and 2 and Table 1, in the case of the positive electrode active materials of Examples 1 and 2, it can be confirmed that the secondary particles contain a plurality of primary particles aggregated, and the average particle size of the plurality of primary particles measured from the SEM image is 1.5 μm or more and 5.0 μm or less. Further, it can be confirmed that the plurality of primary particles contain three or more disk-shaped primary particles. At this time, the disk-shaped primary particle means that in the primary particle observed from the SEM image of the surface or cross-section of the secondary particle, for two boundary lines of the primary particle existing within an angle of 45° or less with respect to the major axis direction, virtual tangents with the most contacts respectively are drawn, and when one virtual line crossing the two tangents is drawn, the primary particle having the same-side interior angle of 150° or more and 210° or less. For reference, in FIGS. 1 and 2, when virtual yellow tangents with the most contacts respectively are drawn for two boundary lines of the primary particle existing within an angle of 45° or less with respect to the red major axis direction, one virtual line (not shown) crossing the two yellow tangents satisfies the same-side interior angle of 150° or more and 210° or less, and the primary particle corresponding to this case is defined as a disk-shaped primary particle. And it can be confirmed that the disk-shaped primary particle has a minor axis of 0.3 μm or more and an aspect ratio (major axis / minor axis) of 1.5 or more. Also, it can be confirmed that the number of cross-sections of the primary particles per unit area is 1 or more and 100 or less. On the other hand, in the case of the positive electrode active materials of Comparative Examples 1, 2, 4, and 5, it can be confirmed that the average particle size of the primary particles measured from the SEM image is less than 500 nm.

[0167] Experimental Example 2: Particle Analysis 2 The positive electrode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 6 were respectively photographed using a scanning electron microscope (FEI, quanta250 FEG) equipped with EBSD.

[0168] Of these, the size of the cross-section of the secondary particles was observed from the electron backscatter diffraction (EBSD) pattern of the SEM image of the cross-section of the secondary particles taken with respect to the cross-section of the positive electrode active material of Comparative Example 4 (measured under the conditions of acceleration voltage 20kV, WD 16mm, measurement magnification 5,000x (width 16μm × height 16μm), step size 0.025μm), which indicates that the size of the cross-section of the secondary particles is the average particle size (D) of the secondary particles. 50 For the EBSD pattern of the cross-section 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, as shown in Figure 13 (Comparative Example 4). 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 in Table 2 below.

[0169]

number

[0170] [Table 2]

[0171] Referring to Table 2, it can be confirmed that in the case of the positive electrode active materials of Examples 1 and 2, 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 This confirms that the above is true.

[0172] Experimental Example 3: Particle Analysis 3 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 volume diameter at the point where 50% of the volume cumulative distribution of primary particles present in each example and comparative example is obtained. 50 The following measurements were taken and are shown in Table 3 below.

[0173] 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 SEM images of the surface of secondary particles taken on the surface of the positive electrode active material of Examples 1 and 2 and Comparative Examples 1 to 6, projected onto a two-dimensional plane. 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 volume value is calculated using the following formula 5, and the degree of single-particle formation (Dv) corresponding to the volume diameter 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.

[0174]

number

[0175] [Table 3]

[0176] Referring to Table 3, it can be confirmed that in the case of the positive electrode active materials of Examples 1 and 2, the degree of single particle formation is between 1.2 μm and 3.8 μm.

[0177] Experimental Example 4: Particle Analysis 4 Electron spectrochemical analysis (ESCA) was performed on the cathode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 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 content (atomic %) of B and Co in the coating layers with thicknesses from 0 to 100 nm was measured. The results are shown in Tables 4 (B coating layer) and 5 (Co coating layer), respectively.

[0178] EPMA cross-sectional analysis was performed on the positive electrode active materials of Examples 1 and 2 to confirm their surface coating properties. First, the positive electrode active material of Example 1, carbon black conductive material, and PVDF binder were mixed in a weight ratio of 95:2:3 in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to one side of an aluminum current collector, dried at 130°C, and then rolled to produce a positive electrode with an electrode porosity of 20%. To create a flat surface for EPMA cross-sectional analysis, the positive electrode was subjected to Ar-ion milling at an acceleration voltage of 6kV using a HITACHI IM-5000 instrument to obtain a cross-section of the positive electrode sample. Then, cross-sectional images of the positive electrode sample were observed using a JEOL JXA-iHP200F instrument at an acceleration voltage of 15kV and a probe current of 50nA, and are shown in Figures 14 and 15, respectively.

[0179] [Table 4]

[0180] [Table 5]

[0181] Referring to the SEM images in Figures 1 and 2, the EPMA images in Figures 14 and 15, and Tables 4 and 5, it can be seen that in the case of the positive electrode active materials of Examples 1 and 2, 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. It can also be seen that the coating portion has both the form of islands 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 the form of a coating layer formed surrounding the surface of the primary particles, the interface of the primary particles, and / or the surface of the secondary particles.

[0182] Experimental Example 5: Volume Cumulative Distribution Analysis The positive electrode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 6 were subjected to a particle size analyzer (PSD, Malvern, martersizer 3500) and 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 top of the y-axis of the peak appearing in the mode of 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 below.

[0183] Then, the skewness value (S) is calculated using equation 3 below, and the y value (P) of the peak point at the top of the y axis of the peak that appears in the mode of the volume cumulative distribution is obtained. MODE The ratio of the skewness value (S) to (S / P) MODE The values ​​were calculated and are shown in Table 6 below.

[0184]

number

[0185] [Table 6]

[0186] Referring to Table 6, in the case of the positive electrode active material of Examples 1 and 2, the D 50 It can be confirmed that it is between 7.0 μm and 20.0 μm. Also, (θ L -θ R It can be confirmed that the value is between 6 and 20. Furthermore, 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 the particle diameter as the x-value increases from left to right on a linear scale, and the y-axis representing the weight distribution as the y-value increases from bottom to top, it can be confirmed that it exhibits positive skewness.

[0187] Experimental Example 6: Measurement of Rolling Density Using an automatic pellet press (Carver, 3887.4), the zero point for thickness was adjusted using a cylindrical die on a circular pellet holder with a diameter of 13 mm. Next, 3 g each of the positive electrode active material produced in Examples 1 and 2 and Comparative Examples 1 to 6 was placed in the circular pellet holder, and the thickness of the formed pellets was measured by applying a force equivalent to 9,000 kgf. 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.

[0188] [Formula 4] Pellet volume (cm³) 3 ) = π (radius of the circular pellet holder) 2 × Pellet thickness

[0189] [Formula 2] Rolling density (g / cm³) 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm³) 3 )

[0190] [Table 7]

[0191] Referring to Table 7, for the positive electrode active materials of Examples 1 and 2, the rolling density is 3.60 g / cm³. 3 This confirms that the above is true.

[0192] Experimental Example 7: Measurement of BET specific surface area The specific surface area was measured by nitrogen gas adsorption and desorption. Specifically, after measuring the weight of an empty cell, 3 g each of the positive electrode active material produced in Examples 1 and 2 and Comparative Examples 1 to 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. The BET specific surface area was measured from the amount of nitrogen gas adsorbed using a gas adsorption analyzer (Micromeritics TriStarr II) under a nitrogen atmosphere, and is shown in Table 8 below.

[0193] [Table 8]

[0194] Referring to Table 8, for the positive electrode active materials of Examples 1 and 2, the BET specific surface area is 0.20 m². 2 / g or more 0.35m 2 It can be confirmed that the amount is less than / g.

[0195] Experimental Example 8: Manufacturing and charge / discharge evaluation of coin-type half-cells A positive electrode slurry was prepared by mixing 95 parts by weight of the respective positive electrode active material produced in Examples 1 and 2 and Comparative Examples 1 to 6, 2 parts by weight of conductive material (Denka, FX35), and 3 parts by weight of binder (KUREHA, KF9709) in an N-methylpyrrolidone (NMP) solvent. The positive electrode slurry prepared above was applied to one side of a 20 μm thick aluminum current collector, and the positive electrode was produced by rolling it so that the porosity of the positive electrode active material layer was 24 volume%.

[0196] 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 then 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), and dimethyl carbonate (DMC) in a volume ratio of 3:3:4.

[0197] Using lithium secondary batteries containing the positive electrode active materials of Examples 1 and 2 and Comparative Examples 1 to 6 manufactured as described above, charging was performed in CC / CV mode at a constant current of 0.1C at 25°C up to 4.25V (termination current 0.05C). Subsequently, the charging and discharging capacities were measured while discharging in CC mode until the voltage reached 2.5V, and the results are shown in Table 3 below. In this process, 1C = 200mA / g was set.

[0198] Furthermore, the lithium secondary batteries manufactured as described above were charged in CC / CV mode at 45°C with a constant current of 0.5C to 4.25V (termination current 0.05C), and then discharged in CC mode with a constant current of 1.0C until the voltage reached 2.5V. This process was repeated 50 times, and 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, as shown in Table 9 below.

[0199] [Table 9]

[0200] Experimental Example 9: Evaluation of High-Rate Discharge Capacity Using the lithium secondary battery manufactured in Experimental Example 8, the battery was charged in CC / CV mode to 4.25V with a constant current of 0.5C at 25°C (termination current 0.05C), and then discharged in CC mode with a constant current of 0.1C until it reached 2.5V, while measuring the discharge capacity. The same procedure was followed by charging in CC / CV mode to 4.25V with a constant current of 0.5C at 25°C (termination current 0.05C), and then discharged in CC mode with a constant current of 1.0C until it reached 2.5V, while measuring the discharge capacity. The percentages of the discharge capacity at 0.1C after charging at 0.5C are shown in Table 10 below.

[0201] [Table 10]

[0202] Referring to Tables 9 and 10 above, it can be confirmed that batteries containing the positive electrode active materials of Examples 1 and 2 have a high high-temperature capacity retention rate, low DC resistance, and excellent rate characteristics. In contrast, M 3 In the case of batteries containing the positive electrode active materials of Comparative Examples 1-5, which do not contain Al, Zr, M, the DC resistance is high, the high-temperature capacity retention rate is low, and the rate characteristics are poor. 3Even if all of the above are included, it can be confirmed that the battery containing the positive electrode active material of Comparative Example 6, which does not have a coating layer containing both Co and B, also has problems such as high DC resistance, low high-temperature capacity retention rate, and poor rate characteristics.

[0203] These results indicate 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 was confirmed that not only are cell characteristics such as improved lifespan and reduced gas generation of lithium secondary batteries improved, but density characteristics are also excellent, and energy density is improved.

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, and the particle size of the primary particles is the particle size based on the major axis of the primary particle. Aluminum (Al), zirconium (Zr), and M ３ The lithium transition metal composite oxide includes the M ３ These are metallic elements with an oxidation state of +4 or higher. A positive electrode active material including a coating portion containing cobalt (Co) and boron (B).

2. Said M ３ The positive electrode active material according to claim 1, wherein is one or more selected from the group consisting of titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo), and niobium (Nb).

3. The Al is present in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal composite oxide, the Zr is present in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal composite oxide, and the M ３ The positive electrode active material according to claim 1, wherein the above is contained in an amount of 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal composite oxide.

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

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

6. 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.

7. The cathode active material according to claim 1, wherein the plurality of primary particles include single-crystal primary particles.

8. 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 of the ) is 7.0 μm or more and 20.0 μm or less.

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

10. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, as described in claim 9.

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