WO2024225849A1

WO2024225849A1 - Cathode active material, cathode, and lithium secondary battery

Info

Publication number: WO2024225849A1
Application number: PCT/KR2024/005812
Authority: WO
Inventors: 이정욱; 조승범; 정진후; 정명기; 황주경; 이지영; 류현모; 허국진; 박상은; 김종혁
Original assignee: 주식회사 엘지화학
Priority date: 2023-04-28
Filing date: 2024-04-29
Publication date: 2024-10-31

Abstract

The present invention relates to a cathode active material and, to a cathode active material, a cathode comprising same, and a lithium secondary battery, the cathode active material enabling problems of conventional secondary particles and problems of discrete particles to be solved simultaneously, and comprising: as primary particles, particles such as conventional discrete particles; and secondary particles formed by aggregating a plurality of primary particles, and thus the present invention has cell characteristics such as improved lifespan of a lithium secondary battery and reduced gas generation, and also has excellent density characteristics so as to have improved energy density.

Description

Cathode active material, cathode and lithium secondary battery

Cross-reference with related applications

This application claims the benefit of priority to Korean Patent Application No. 10-2023-0056231, filed April 28, 2023, and Korean Patent Application No. 10-2024-0057077, filed April 29, 2024, the entire contents of which are incorporated herein by reference.

Technical field

The present invention relates to a cathode active material, a cathode including the same, and a lithium secondary battery.

Recently, with the advancement of technology such as electric vehicles, the demand for high-capacity secondary batteries is increasing, and accordingly, research on high-nickel (High Ni) cathode active materials with excellent capacity characteristics is being actively conducted.

The high nickel cathode active material formed by the secondary particle structure in which the primary particles are aggregated undergoes structural degradation during the charging and discharging of the lithium secondary battery, but relatively, the lattice structure constant changes, that is, the volume change within the unit cell occurs significantly. This volume change causes cracks in the cathode active material. In addition, cracks may occur in the cathode active material due to pressure during electrode rolling.

The cracks in the high nickel positive electrode active material that occur in this way become more severe during the charging and discharging process of the lithium secondary battery, and as a result, they act as voids that cannot reach the electrolyte or reduce conductivity, which reduces the life characteristics of the lithium secondary battery or acts as a factor in increasing resistance.

In order to minimize the occurrence of cracks in such secondary particle structures, attempts are being made to manufacture single-particle cathode active materials. However, such single-particle cathode active materials have a problem in that the particle sizes are non-uniform, and thus the particle size distribution of the single-particle cathode active materials obtained after pulverization is large. In addition, single-particle cathode active materials have a low specific surface area, and thus are vulnerable to cell resistance characteristics.

Therefore, there is a need for the development of a cathode active material that can simultaneously solve the problems of conventional secondary particles and single particles.

Meanwhile, Korean Patent Publication No. 10-1785262 (Patent Document 1) discloses large-diameter secondary particles, which include secondary particles in which primary particles are aggregated, the secondary particles include a nickel-based lithium transition metal oxide, and the average particle diameter of the primary particles is 3 to 5 ㎛ and the average particle diameter of the secondary particles is 10 to 20 ㎛. Such large-diameter secondary particles include primary particles having an average particle diameter on the micron level, thereby improving the rolling density and minimizing cracks caused by rolling, etc., and improving the specific surface area through the secondary particle structure, thereby improving cell characteristics.

In order to manufacture a cathode active material in the form of secondary particles whose primary particles are on the micron level in size, as disclosed in Patent Document 1, it is necessary to perform heat treatment at a higher temperature than that of secondary particles whose primary particles are on the submicron level of less than 1 ㎛ in size. However, as the heat treatment temperature increases, the layered structure of the lithium-transition metal composite oxide degenerates into a rock salt structure, which causes a decrease in crystallinity and, in turn, causes a decrease in the performance of the cathode active material. In particular, since nickel is most vulnerable to the degeneration of the layered structure of the lithium-transition metal composite oxide into a rock salt structure at high heat treatment temperatures, the degeneration becomes more severe when the content of nickel in the lithium-transition metal composite oxide constituting the cathode active material increases. Therefore, conventionally, it could only be applied to mid-nickel (Mid Ni) cathode active materials in which the nickel content among the transition metals of the lithium-transition metal composite oxide was about 50 mol%, as in Patent Document 1, as a cathode active material in the form of secondary particles in which the primary particles are on the micron level in size, and it was not possible to manufacture secondary particle-type cathode active materials in which the primary particles are on the micron level in size for high-nickel (High Ni) cathode active materials with excellent capacity characteristics due to the high nickel content among the transition metals of the lithium-transition metal composite oxide.

[Prior art literature]

[Patent Document]

(Patent Document 1) KR 10-1785262 B1

(Patent Document 2) KR 10-2017-0119573 A

The problem to be solved in the present invention is to provide a cathode active material capable of simultaneously solving the problems of conventional secondary particles and single particles in a high nickel (High Ni) cathode active material.

That is, the present invention has been made to solve the problems of the above-mentioned prior art, and is a high nickel (High Ni) cathode active material having excellent capacity characteristics due to a high content of nickel among the transition metals of the lithium transition metal composite oxide, and by implementing the cathode active material in the form of secondary particles having a primary particle size on the micron level, the present invention provides a cathode active material having excellent density characteristics and thus improving energy density as well as cell characteristics such as improved lifespan and reduced gas generation.

In addition, the present invention aims to provide a positive electrode and a lithium secondary battery including the positive electrode active material.

To solve the above problems, the present invention provides a cathode active material, a cathode including the same, and a lithium secondary battery.

(1) The present invention provides a cathode active material comprising secondary particles in which a plurality of primary particles are aggregated, wherein the plurality of primary particles have an average particle size of 1.5 ㎛ or more and 5.0 ㎛ or less as measured from a SEM image, the particle size of the primary particles is a particle size based on the major diameter of the primary particles, and the secondary particles have an average particle diameter (D50) of 7.0 ㎛ or more and 20.0 ㎛ or less as measured by a laser diffraction particle size analyzer based on a volume cumulative distribution, and wherein the size of the cross-section of the secondary particles observed from a SEM image of the cross-section of the secondary particles is within a range of the average particle diameter (D50) of the secondary particles, and the number of cross-sections of the primary particles confirmed within a unit area of 5 ㎛ in width and 5 ㎛ in length within the cross-section of the secondary particles is 1 or more and 100 or less.

(2) The present invention provides a cathode active material, wherein, in the cross-section of the secondary particle, the size of the cross-section of the secondary particle observed from a SEM image of the cross-section of the secondary particle is within the range of the average particle diameter (D50) of the secondary particle, and the number of cross-sections of the primary particles confirmed within a unit area of 5 ㎛ width x 5 ㎛ length within the cross-section of the secondary particle is 1 or more and 50 or less.

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

(4) The present invention provides a cathode active material comprising a lithium transition metal composite oxide containing nickel at 60 mol% or more among the total transition metals, in any one of (1) to (3) above.

(5) The present invention provides a positive electrode active material comprising a lithium transition metal composite oxide having an average composition represented by the following chemical formula 1, in any one of (1) to (4) above.

[Chemical Formula 1]

Li _x Ni _a Co _b Mn _c M ¹ _d O ₂

In the chemical formula 1, M ¹ is at least one 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.

(6) The present invention provides a positive electrode active material according to any one of (1) to (5), wherein the plurality of primary particles include single crystal primary particles.

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

(8) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (7).

(9) The present invention provides a lithium secondary battery including a positive electrode according to (8); a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

The cathode active material of the present invention is a cathode active material that can simultaneously solve the problems of conventional secondary particles and single particles in high nickel (High Ni) cathode active materials, and by implementing a cathode active material in the form of secondary particles whose primary particles are on the micron level in size, not only does it improve cell characteristics such as improved lifespan and reduced gas generation of a lithium secondary battery, but it also has excellent density characteristics so as to improve energy density.

Figure 1 is an SEM image of (A) the positive electrode active material of Example 1, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 2 is an SEM image of (A) the positive electrode active material of Example 2, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 3 is an SEM image of (A) the positive electrode active material of Example 3, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 4 is an SEM image of (A) the positive electrode active material of Example 4, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 5 is an SEM image of (A) the positive electrode active material of Example 5, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 6 is an SEM image of (A) the positive electrode active material of Example 6, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 7 is an SEM image of (A) the positive electrode active material of Example 7, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 8 is an SEM image of (A) the positive electrode active material of Example 8, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 9 is an SEM image of (A) the positive electrode active material of Example 9, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 10 is an SEM image of (A) the positive electrode active material of Example 10, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 11 is an SEM image of (A) the positive electrode active material of Example 11, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 12 is an SEM image of (A) the positive electrode active material of Comparative Example 1, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 13 shows an SEM image of (A) the positive electrode active material of Comparative Example 2, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 14 shows an SEM image of (A) the positive electrode active material of Comparative Example 3, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 15 is an SEM image of (A) the positive electrode active material of Comparative Example 4, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 16 is an SEM image of (A) the positive electrode active material of Comparative Example 5, and (B) an SEM image of a cross-section of the positive electrode active material.

Figure 17 is a segmentation image showing multiple lithium composite transition metal oxides segmented by performing image analysis based on an artificial intelligence model from the SEM image of the positive electrode active material of Example 1.

Figure 18 is a segmentation image showing multiple lithium composite transition metal oxides segmented by performing image analysis based on an artificial intelligence model from the SEM image of the positive electrode active material of Comparative Example 1.

Figure 19 is a TEM image of a cross-section of the positive active material of Example 1.

Figure 20 is a TEM image of a cross-section of the positive electrode active material of Example 2.

Figure 21 is a TEM image of a cross-section of the positive electrode active material of Example 8.

Figure 22 is an EBSD pattern image of a cross-section of the positive active material of Example 1.

Figure 23 is an EBSD pattern image of a cross-section of the positive active material of Example 2.

Figure 24 is an EBSD pattern image of a cross-section of the positive active material of Example 3.

Figure 25 is an EBSD pattern image of a cross-section of the positive active material of Example 4.

Figure 26 is an EBSD pattern image of a cross-section of the positive active material of Example 8.

Figure 27 is an EBSD pattern image of a cross-section of the positive active material of Example 10.

Figure 28 is an EBSD pattern image of a cross-section of the positive active material of Example 11.

Figure 29 is an EBSD pattern image of a cross-section of the positive electrode active material of Comparative Example 3.

Figure 30 is an EPMA analysis image of the positive electrode active material of Example 1.

Figure 31 is a graph of the cumulative volume distribution of the positive electrode active material of Example 1 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 32 is a graph of the cumulative volume distribution of the positive electrode active material of Example 2 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 33 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 3, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 34 is a graph of the cumulative volume distribution of the positive electrode active material of Example 4 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 35 is a graph of the cumulative volume distribution of the positive electrode active material of Example 5 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 36 is a graph of the cumulative volume distribution of the positive electrode active material of Example 6 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 37 is a graph of the cumulative volume distribution of the positive electrode active material of Example 7 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 38 is a graph of the cumulative volume distribution of the positive electrode active material of Example 8 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 39 is a graph of the cumulative volume distribution of the positive electrode active material of Example 9 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 40 is a graph of the cumulative volume distribution of the positive electrode active material of Example 10 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 41 is a graph of the cumulative volume distribution of the positive electrode active material of Example 11 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 42 is a graph of the cumulative volume distribution of the positive electrode active material of Comparative Example 1 measured using a laser diffraction particle size analyzer, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 43 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Comparative Example 3, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 44 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 1, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 45 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 2, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 46 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 3, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 47 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 4, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 48 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 5, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 49 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 6, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 50 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 7, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 51 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 8, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 52 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 9, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 53 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 10, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 54 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Example 11, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 55 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Comparative Example 1, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Figure 56 is a frequency distribution graph showing the volume cumulative distribution measured using a laser diffraction particle size analyzer for the positive electrode active material of Comparative Example 3, in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Hereinafter, the present invention will be described in more detail to help understand the present invention.

The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to explain his or her own invention in the best manner.

In the present invention, the term 'primary particle' means the smallest particle unit that can be distinguished as a single lump when observing the cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal or multiple crystal grains.

In the present invention, the term 'secondary particle' refers to a secondary structure formed by agglomeration of multiple primary particles. The average particle diameter of the secondary particles can be measured using a particle size analyzer.

In the present invention, the term 'average particle diameter ( _D50 )' means the particle diameter at the 50% point of the volume cumulative distribution according to particle diameter. The average particle diameter can be measured by dispersing the target powder in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., S3500 from Microtrac), and measuring the difference in diffraction patterns according to particle size when the particles pass through the laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle diameter in the measuring device, thereby measuring _D50 .

In the present invention, the term 'major axis of a primary particle' refers to the length of the longest line segment when a line is drawn passing through two points of a primary particle boundary in a primary particle observed from an SEM image of the surface or cross-section of a secondary particle.

In the present invention, the term 'shortest diameter of a primary particle' refers to the length of the shortest line segment when a line is drawn passing through two points of a primary particle boundary in a primary particle observed from an SEM image of the surface or cross-section of a secondary particle.

Bipolar active material

The present invention provides a positive electrode active material.

According to one embodiment of the present invention, a plurality of primary particles may include secondary particles in which the plurality of primary particles are aggregated, and the plurality of primary particles may have an average particle size measured from a SEM image of 1.5 ㎛ or more and 5.0 ㎛ or less.

According to one embodiment of the present invention, the secondary particle may be a secondary particle formed by agglomeration of a plurality of primary particles, and may be a secondary particle formed by agglomeration of at least two, specifically, at least three or more primary particles.

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

According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide including nickel, cobalt, and manganese. As a specific example, the positive electrode active material may include a lithium transition metal composite oxide including nickel at 60 mol% or more among the total transition metals. The lithium transition metal composite oxide may be a primary particle, a secondary particle, and the positive electrode active material itself including these, and as a specific example, the positive electrode active material may include a secondary particle in which a plurality of primary particles formed of the lithium transition metal composite oxide are aggregated.

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.

[Chemical Formula 1]

Li _x Ni _a Co _b Mn _c M ¹ _d O ₂

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

According to one embodiment of the present invention, in the chemical formula 1, a, b, c, and d may be mole fractions of nickel (Ni), cobalt (Co), manganese (Mn) among transition metals, and a doping element (M ¹ ), respectively. As a specific example, a may be a mole fraction of nickel (Ni) among 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 further may be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. In addition, the b may be a mole fraction of cobalt (Co) among the transition metals, greater than 0, 0.01, 0.02, or 0.03, and further may 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. The c may be a mole fraction of manganese (Mn) among the transition metals, greater than 0, 0.01 or more, or 0.05 or more, and further may 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. The above d is a mole fraction of a doping element (M ¹ ) among transition metals and may be 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, or 0.19 or more, and further, 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, It can be 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. When the composition of the lithium transition metal composite oxide is adjusted as above, the capacity can be further improved.

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

According to one embodiment of the present invention, the secondary particles may have an average particle diameter ( _D50 ) of 7.0 ㎛ or more and 20.0 ㎛ or less based on a volume cumulative distribution measured using a laser diffraction particle size analyzer. As a specific example, the secondary particles may have an average particle diameter ( _D50 ) of 7.0 ㎛ or more, 7.1 ㎛ or more, 7.2 ㎛ or more, 7.3 ㎛ or more, 7.4 ㎛ or more, 7.5 ㎛ or more, 7.6 ㎛ or more, 7.7 ㎛ or more, 7.8 ㎛ or more, 7.9 ㎛ or more, 8.0 ㎛ or more, 8.1 ㎛ or more, 8.2 ㎛ or more, 8.3 ㎛ or more, 8.4 ㎛ or more, 8.5 ㎛ or more, 8.6 ㎛ or more, 8.7 ㎛ or more, 8.8 ㎛ or more, 8.9 ㎛ or more, or 9.0 ㎛ or more, and further, 20.0 ㎛ or less, 19.9 ㎛ or less, 19.8 ㎛ or less, 19.7 ㎛ or less, 19.6 ㎛ or less, 19.5 ㎛ or less, 19.4 ㎛ or less, 19.3 ㎛ or less, 19.2 ㎛ or less, 19.1 ㎛ or less, 19.0 ㎛ or less, 18.9 ㎛ or less, 18.8 ㎛ or less, 18.7 ㎛ or less, 18.6 ㎛ or less, 18.5 ㎛ or less, 18.4 ㎛ or less, 18.3 ㎛ or less, 18.2 ㎛ or less, 18.1 ㎛ or less, 18.0 ㎛ or less, 17.9 ㎛ or less, 17.8 ㎛ or less, 17.7 ㎛ or less, 17.6 ㎛ or less, 17.5 ㎛ or less, 17.4 ㎛ or less, 17.3 ㎛ or less, 17.2 ㎛ or less, 17.1 ㎛ or less, 17.0 ㎛ or less, 16.9 ㎛ or less, It may be 16.8 ㎛ or less, 16.7 ㎛ or less, 16.6 ㎛ or less, 16.5 ㎛ or less, 16.4 ㎛ or less, 16.3 ㎛ or less, 16.2 ㎛ or less, 16.1 ㎛ or less, 16.0 ㎛ or less, 15.9 ㎛ or less, 15.8 ㎛ or less, 15.7 ㎛ or less, 15.6 ㎛ or less, 15.5 ㎛ or less, 15.4 ㎛ or less, 15.3 ㎛ or less, 15.2 ㎛ or less, 15.1 ㎛ or less, or 15.0 ㎛ or less. Within this range, the rolling density of the positive electrode active material can be further improved, and the lifespan can be further improved.

As a specific example, the cathode active material may be a high nickel cathode active material including a lithium transition metal composite oxide containing nickel at 60 mol% or more among the total transition metal, wherein a plurality of primary particles may include secondary particles having a large particle size (D50) of 7.0 ㎛ or more and 20.0 ㎛ or less, which are formed by agglomeration of primary particles having a particle size of 0.5 ㎛ or more and 5.0 ㎛ or less, specifically, _micron -level primary particles of 1.0 ㎛ or more, and more specifically, a plurality of primary particles having an average particle size of 2.0 ㎛ or more and 3.5 ㎛ or less as measured from a SEM image, and in the sense that primary particles in the form of single particles agglomerate to form large particles in the form of secondary particles, it may be expressed as a large particle single particle cluster.

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 having a primary particle size of micron-level, it is necessary to perform heat treatment at a higher temperature than that of secondary particles having a primary particle size of less than 1 ㎛ in submicron-level. However, as the heat treatment temperature increases, the layered structure of the lithium-transition metal composite oxide degenerates into a rock salt structure, which causes a decrease in crystallinity and, in turn, causes a decrease in the performance of the cathode active material. In particular, since nickel is most vulnerable to the degeneration of the layered structure of the lithium-transition metal composite oxide into a rock salt structure at high heat treatment temperatures, the degeneration is further aggravated when the content of nickel in the lithium-transition metal composite oxide constituting the cathode active material increases. Therefore, in the past, it was only possible to apply the method to a mid-nickel cathode active material in which the nickel content of the transition metal of the lithium-transition metal composite oxide was about 50 mol%, as a cathode active material in the form of secondary particles in which the primary particles are on the micron level in size, and it was impossible to manufacture a cathode active material in the form of secondary particles in which the primary particles are on the micron level in size for a high-nickel cathode active material in which the nickel content of the transition metal of the lithium-transition metal composite oxide is high and thus has excellent capacity characteristics.

However, since the positive electrode active material of the present invention has a high content of nickel among the transition metals of the lithium-transition metal composite oxide, even if the layered structure of the lithium-transition metal composite oxide degenerates into a rock salt structure at a high heat treatment temperature, the rock salt structure is recovered into a layered structure, thereby solving the aforementioned problem. Specifically, unlike a conventional mid-nickel positive electrode active material, the positive electrode active material of the present invention is a high-nickel positive electrode active material including a lithium-transition metal composite oxide containing nickel at 60 mol% or more of the total transition metal, and while including secondary particles having a primary particle size on the micron level, the rock salt structure formed by the high heat treatment temperature is recovered into a layered structure, so that the crystallinity of the lithium-transition metal composite oxide is excellent, and thus the problems of the conventional secondary particles and the problems of the single particles can be solved at the same time. The positive electrode active material of the present invention can be manufactured by restoring the rock salt structure formed by the high heat treatment temperature into a layered structure as described above, and the method of restoring the rock salt structure into a layered structure is not limited, but according to one embodiment of the present invention, the method of restoring the rock salt structure into a layered structure may be to perform cobalt (Co) coating on a lithium transition metal composite oxide including the rock salt structure formed by the high heat treatment temperature.

According to one embodiment of the present invention, the plurality of primary particles may include disk-type primary particles, and as a specific example, may include three or more disk-type primary particles, in which case the cell has excellent lifespan and energy density.

According to one embodiment of the present invention, the disk-shaped primary particle may mean that, in the primary particle observed from an SEM image of the surface or cross-section of the secondary particle, when two imaginary tangent lines having the largest number of contact points are drawn for each of the two boundaries of the primary particle existing within an angle of 45° or less with respect to the major axis direction, and one imaginary line crossing the two tangent lines is drawn, the coplanar internal angle is 150° or more and 210° or less, the minor axis of the primary particle is 0.3 ㎛ or more, and the aspect ratio (major axis/minor axis) is 1.5 or more. As a specific example, the disk-shaped primary particle may have a primary particle diameter of 0.3 ㎛ or more, 0.4 ㎛ or more, 0.5 ㎛ or more, 0.6 ㎛ or more, 0.7 ㎛ or more, 0.8 ㎛ or more, 0.9 ㎛ or more, or 1.0 ㎛ or more. Here, when the disk-shaped primary particle has a primary particle diameter of 0.3 ㎛ or more and an aspect ratio (major axis/minor axis) of 1.5 or more, the area ratio of the (003) plane among the crystal planes on the surface of the primary particle may be the largest.

According to one embodiment of the present invention, the disk-shaped primary particle may mean that, in the primary particle observed from the SEM image of the surface or cross-section of the secondary particle, when two imaginary tangent lines having the largest number of contact points are drawn for each of the primary particles existing within an angle of 45° or less with respect to the major axis direction, and one imaginary line crossing the two tangent lines is drawn, the coaxial 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 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 primary particle of the disk-shaped primary particle is the largest, the primary particle may have a minor axis of 0.3 ㎛ or more and an aspect ratio (major axis/minor axis) of 1.5 or more. That is, the largest area ratio of the (003) plane among the crystal planes on the surface of the primary particle can be confirmed from the fact that the minor axis of the primary particle is 0.3 ㎛ or more and the aspect ratio (major axis/minor axis) is 1.5 or more.

According to one embodiment of the present invention, the positive electrode active material may be a frequency distribution graph in which the x-axis represents a volume cumulative distribution measured using a laser diffraction particle size analyzer in a log scale for particle diameters in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top, wherein, when a triangle is drawn with a peak point at the uppermost point of the y-axis of a peak appearing in a mode; and two contact points of the frequency distribution curves that touch at the half width at half maximum (FWHM) of the mode, the difference (θ _L - θ _R ) between the internal angle (θ _L ) at the left contact point and the internal angle (θ _R ) at the right contact point among the two contact points of the frequency distribution curves that touch at the half width may be 6 or more and 20 or less. As a specific example, the difference (θ _L - θ _R ) between the interior angle (θ _L ) at the left contact point and the interior angle (θ _R ) at the right contact point 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 active material may have a ratio of the interior angle at the left contact point to the interior angle at the right contact point (θ _L /θ _R ) of 1.100 or more and 2.000 or less. As a specific example, the ratio of the interior angle at the left contact point to the interior angle at the right contact point (θ _L /θ _R ) is 1.100 or more, 1.110 or more, 1.120 or more, 1.130 or more, 1.140 or more, 1.150 or more, 1.160 or more, 1.170 or more, 1.180 or more, 1.190 or more, 1.200 or more, 1.210 or more, 1.220 or more, 1.230 or more, 1.240 or more, 1.250 or more, 1.260 or more, 1.270 or more, 1.280 or more, 1.290 or more, 1.300 or more, 1.310 or more, 1.320 or more, 1.330 or more, 1.340 or more, 1.350 or more, 1.360 or more, It may be 1.370 or more, 1.380 or more, 1.390 or more, 1.400 or more, 1.410 or more, 1.420 or more, 1.430 or more, or 1.440 or more, and may also be 1.450 or less, 1.460 or less, 1.470 or less, 1.480 or less, 1.490 or less, 1.500 or less, 1.550 or less, 1.600 or less, 1.650 or less, 1.700 or less, 1.750 or less, 1.800 or less, 1.850 or less, 1.900 or less, 1.950 or less, or 2.000 or less. Here, the frequency distribution graph may be a unimodal distribution graph.

According to one embodiment of the present invention, the positive 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 represented by a linear scale for particle diameter in which the x-axis represents the x-value increasing from left to right, and the y-axis represents the weight distribution in which the y-value increasing from bottom to top. Here, the frequency distribution graph may be a unimodal distribution graph.

According to one embodiment of the present invention, the positive electrode active material may have a ratio (S/P MODE) of a skewness value (S) to a y-value (P _MODE ) of a peak point at the uppermost y-axis of a peak appearing in a mode ( _Mode ) according to a volume cumulative distribution of 0.037 or more and 0.150 or less. As a specific example, the positive electrode active material has a ratio (S/P _MODE ) of the skewness value (S) to the y-value (P _MODE ) of the peak point at the top of the y-axis of the peak appearing in the mode (Mode) according to the volume cumulative distribution of 0.037 or more, 0.038 or more, 0.039 or more, 0.040 or more, 0.041 or more, 0.042 or more, 0.043 or more, 0.044 or more, 0.045 or more, 0.046 or more, 0.047 or more, 0.048 or more, 0.049 or more, 0.050 or more, 0.051 or more, 0.052 or more, 0.053 or more, 0.054 or more, 0.055 or more, 0.056 or more, 0.057 or more, 0.058 or more, 0.059 or more, 0.060 or higher, 0.061 or higher, 0.062 or higher, 0.063 or higher, 0.064 or higher, 0.065 or higher, 0.066 or higher, 0.067 or higher, 0.068 or higher, 0.069 or higher, 0.070 or higher, 0.071 or higher, 0.072 or higher, 0.073 or higher, 0.074 or higher, 0.075 or higher, 0.076 or higher, 0.077 or higher, 0.078 or higher, 0.079 or higher, 0.080 or higher, 0.081 or higher, 0.082 or higher, 0.083 or higher, 0.083 or higher, 0.084 or higher, 0.085 or higher, 0.086 or higher, 0.087 or higher, 0.088 or higher, 0.089 It may be 0.090 or more, 0.091 or more, 0.092 or more, 0.093 or more, 0.094 or more, 0.095 or more, 0.096 or more, 0.097 or more, 0.098 or more, 0.099 or more, or 0.100 or more, 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 from the following Equation 3.

[Formula 3]

According to one embodiment of the present invention, the positive electrode active material may have a BET specific surface area measured through nitrogen adsorption BET specific surface area analysis of 0.20 m ² /g or more and 0.35 m ² /g or less. As a specific example, the positive active material may have a BET surface area measured through nitrogen adsorption BET surface area analysis of 0.20 m ² /g or more, 0.21 m ² /g or more, 0.22 m ² /g or more, 0.23 m ² /g or more, 0.24 m ² /g or more, 0.25 m ² /g or more, 0.26 m ² /g or more, 0.27 m ² /g or more, 0.28 m ² /g or more, 0.29 m ² /g or more, 0.30 m ² /g or more, or 0.31 m ² /g or more, and further may have 0.35 m ² /g or less, or 0.34 m ² /g or less. Within this range, the DC resistance can be reduced and the rolling density can be improved.

According to one embodiment of the present invention, the positive electrode active material may have an average particle diameter ( _D50 ) of 7.0 ㎛ or more and 20.0 ㎛ or less according to a volume cumulative distribution measured using a laser diffraction particle size analyzer for the secondary particles, and a size of a cross-section of the secondary particles observed from a SEM image of a cross-section of the secondary particles is within a range of the average particle diameter ( _D50 ) of the secondary particles, and the number of cross-sections of primary particles confirmed within a unit area of 5 ㎛ in width x 5 ㎛ in length within the cross-section of the secondary particles may be 1 or more and 100 or less.

As a specific example, the positive active material includes secondary particles in which a plurality of primary particles are aggregated, and the plurality of primary particles have an average particle size of 1.5 ㎛ or more and 5.0 ㎛ or less as measured from an SEM image, the particle size of the primary particles is a particle size based on the major diameter of the primary particles, and the secondary particles have an average particle diameter (D50) of 7.0 ㎛ or more and 20.0 ㎛ or less according to a volume cumulative distribution measured using a laser diffraction particle size analyzer, and the size of the cross-section of the secondary particles observed from an SEM image of the cross-section of the secondary particles is within a range of the average particle diameter (D50) of the secondary particles, and the number of cross-sections of the primary particles confirmed within a unit area of 5 ㎛ in width and 5 ㎛ in length within the cross-section of the secondary particles may be 1 or more and 100 or less.

According to one embodiment of the present invention, for a cross-section of a secondary particle having a size within the range of an average particle diameter ( _D50 ) of the secondary particle as observed from a SEM image of the cross-section of the secondary particle, the number of cross-sections of primary particles confirmed within a unit area of 5 ㎛ width * 5 ㎛ height within the cross-section of the secondary particle means the number of cross-sections of all primary particles that include at least a part of the cross-sections of the primary particles in addition to all cross-sections of the primary particles confirmed within the unit area. In addition, the unit area of 5 ㎛ width * 5 ㎛ height 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 location is not limited as long as it is within the cross-section of the secondary particle.

According to one embodiment of the present invention, the cathode active material has a cross-section of the secondary particle, the size of which is within the range of the average particle diameter (D ₅₀ ) of the secondary particle, as observed from the SEM image of the cross-section of the secondary particle, and the number of primary particle cross-sections confirmed within a unit area of 5 ㎛ width x 5 ㎛ length within the cross-section of the secondary particle is It can be 1 or more and 100 or less, and for specific examples, it can 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, and also can be 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, or 25 or less. When such a range is satisfied, the positive electrode active material may be represented as including a plurality of primary particles having a particle size of 0.5 ㎛ or more and 5.0 ㎛ or less, such as a conventional single particle, specifically a micron-level primary particle of 1.0 ㎛ or more, and more specifically a secondary particle having a large particle size ( _D50 ) of 7.0 ㎛ or more and 20.0 ㎛ or less, formed by agglomeration of a plurality of primary particles having an average particle size of 2.0 ㎛ or more and 3.5 ㎛ or less as measured from a SEM image.

According to one embodiment of the present invention, the cathode active material may have an average particle diameter ( _D50 ) of 7.0 ㎛ or more and 20.0 ㎛ or less according to a volume cumulative distribution measured using a laser diffraction particle size analyzer for the secondary particles, and a size of a cross-section of the secondary particles observed from an backscattered electron diffraction (EBSD) pattern of an SEM image of a cross-section of the secondary particles (measured under the conditions of an acceleration voltage of 20 kV, a WD of 16 mm, a measurement magnification of 5,000 times (width 16 ㎛ * height 16 ㎛), and a step size of 0.025 ㎛) may be within a range of the average particle diameter ( _D50 ) of the secondary particles, and the number of cross-sections of grains confirmed within a unit area of 5 ㎛ in width * 5 ㎛ in the cross-section of the secondary particles may be 1 or more and 150 or less.

According to one embodiment of the present invention, for a cross-section of a secondary particle, the size of the cross-section of the secondary particle observed from an electronic beam spread spectrum (EBSD) pattern of a SEM image (measured under the conditions of an acceleration voltage of 20 kV, a WD of 16 mm, a measurement magnification of 5,000 times (width 16 ㎛ * height 16 ㎛), and a step size of 0.025 ㎛) is within a range of an average particle diameter (D ₅₀ ) of the secondary particle, the number of cross-sections of grains confirmed within a unit area of 5 ㎛ in width * 5 ㎛ in length within the cross-section of the secondary particle means the number of cross-sections of all grains that are included in addition to all cross-sections of grains confirmed within the unit area, even if only a part of the cross-sections of the grains is included. In addition, the unit area of 5 ㎛ width x 5 ㎛ height within the cross-section of the secondary particle is the unit area at any point within the cross-section of the secondary particle, and there is no limitation on the location within the cross-section of the secondary particle.

According to one embodiment of the present invention, the cathode active material may be such that the size of the cross-section of the secondary particle, as observed from the backscattered electron diffraction (EBSD) pattern of the SEM image of the cross-section of the secondary particle (measured under the conditions of acceleration voltage 20 kV, WD 16 mm, measurement magnification 5,000 times (width 16 ㎛ * height 16 ㎛), step size 0.025 ㎛), is within the range of the average particle diameter (D ₅₀ ) of the secondary particle, and the number of cross-sections of grains confirmed within a unit area of 5 ㎛ width * 5 ㎛ height within the cross-section of the secondary particle may be 1 or more and 150 or less, and as specific examples, 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, and further, 150 or less, It may be 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. When such a range is satisfied, the positive electrode active material may be represented as including a plurality of primary particles having a particle size of 0.5 ㎛ or more and 5.0 ㎛ or less, such as a conventional single particle, specifically a micron-level primary particle of 1.0 ㎛ or more, and more specifically a secondary particle having a large particle size ( _D50 ) of 7.0 ㎛ or more and 20.0 ㎛ or less, formed by agglomeration of a plurality of primary particles having an average particle size of 2.0 ㎛ or more and 3.5 ㎛ or less as measured from a SEM image.

According to one embodiment of the present invention, the positive electrode active material may have a single crystallinity of 0.15 ㎛ ³ or more as calculated from the following equation 1.

[Formula 1]

In the above equation 1, radius(grain) is the area of the cross-section of all grains that can be confirmed in the cross-section of the secondary particle having a size within the range of the average particle diameter (D50) of the secondary particle, as observed from the backscattered electron diffraction (EBSD) pattern of the SEM image of the cross-section of the secondary particle (measured under the conditions of acceleration voltage 20 kV, WD ₁₆ mm, measurement magnification 5,000 times (width 16 ㎛ * height 16 ㎛), step size 0.025 ㎛). For grains with a cross-section of 0.196 ㎛ ² or more, this is the radius of the cross-section of the grain assuming that the cross-section of the grain is circular, and n is the number of grains.

According to one embodiment of the present invention, the cathode active material may have a single crystallinity calculated from Equation 1 of 0.15 ㎛ ³ or more and 12.70 ㎛ ³ or less. As a specific example, the cathode active material may have a single crystallinity calculated from the above formula 1 of 0.15 ㎛ ³ or more, 0.20 ㎛ ³ or more, 0.25 ㎛ ³ or more, 0.30 ㎛ ³ or more, 0.35 ㎛ ³ or more, 0.40 ㎛ ³ or more, 0.45 ㎛ ³ or more, 0.50 ㎛ ³ or more, 0.55 ㎛ ³ or more, 0.60 ㎛ ³ or more, 0.65 ㎛ ³ or more, 0.70 ㎛ ³ or more, 0.75 ㎛ ³ or more, 0.80 ㎛ ³ or more, 0.85 ㎛ ³ or more, 0.90 ㎛ ³ or more, 0.95 ㎛ ³ or more, 1.00 ㎛ ³ or more, or 1.05 ㎛ ³ or more, and further, the upper limit is not particularly limited. However, it may be 20.00 ㎛ ³ or less, 19.00 ㎛ ³ or less, 18.00 ㎛ ³ or less, 17.00 ㎛ ³ or less, 16.00 ㎛ ³ or less, 15.00 ㎛ ³ or less, 14.00 ㎛ ³ or less, 13.00 ㎛ ³ or less, or 12.70 ㎛ ³ or less.

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

According to one embodiment of the present invention, the aluminum (Al) may be included in an amount of 500 ppm to 3,000 ppm based on the total weight of the lithium transition metal composite oxide. As a specific example, the aluminum (Al) may be included in an amount of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more based on the total weight of the lithium transition metal composite oxide, and further may be included in an amount of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

According to one embodiment of the present invention, the yttrium (Y) may be included in an amount of 100 ppm to 2,000 ppm based on the total weight of the lithium transition metal composite oxide. As a specific example, the yttrium (Y) may be included in an amount of 100 ppm or more, 200 ppm or more, 300 ppm or more, 400 ppm or more, or 500 ppm or more based on the total weight of the lithium transition metal composite oxide, and further may be included in an amount 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.

According to one embodiment of the present invention, the zirconium (Zr) may be included in an amount of 500 ppm to 5,000 ppm based on the total weight of the lithium transition metal composite oxide. As a specific example, the zirconium (Zr) may be included in an amount of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more based on the total weight of the lithium transition metal composite oxide, and further may be included 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.

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.

[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

In the above chemical formula 2, M ² is at least one selected from the group consisting of B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, A is at least one selected from the group consisting of F, Cl, Br, I, and S, and 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.

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

According to one embodiment of the present invention, in the chemical formula 2, a, b, c, d, e, f, and g may be mole fractions of nickel (Ni), cobalt (Co), manganese (Mn), a doping element (M ² ), aluminum (Al), yttrium (Y), and zirconium (Zr) among transition metals, respectively. As a specific example, a may be a mole fraction of nickel (Ni) among 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 further may be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. In addition, the b may be a mole fraction of cobalt (Co) among the transition metals, greater than 0, 0.01, 0.02, or 0.03, and further may 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. The c may be a mole fraction of manganese (Mn) among the transition metals, greater than 0, 0.01 or more, or 0.05 or more, and further may 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. The above d is a mole fraction of a doping element (M ² ) among transition metals and may be 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, or 0.19 or more, and further, 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, It may be 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 e is a mole fraction of aluminum (Al) among 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 further may be 0.01 or less, 0.009 or less, or 0.008 or less. The above f is a mole fraction of yttrium (Y) among transition metals, and may be greater than 0, 0.0001 or more, 0.0002 or more, or 0.0003 or more, and further may be 0.0006 or less, 0.0005 or less, or 0.0004 or less. The above g is a mole fraction of zirconium (Zr) among transition metals, and may be greater than 0, 0.0001 or more, or 0.0002 or more, and further may be 0.0005 or less, or 0.0004 or less.

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

According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide including aluminum (Al), zirconium (Zr), and M ³ . As a specific example, the positive electrode active material may include aluminum (Al), zirconium (Zr), and M ³ as doping elements.

According to one embodiment of the present invention, the M ³ may be a metal element having an oxidation number of +4 or higher. As a specific example, the M ³ may be at least one selected from the group consisting of titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo), and niobium (Nb).

According to one embodiment of the present invention, the zirconium (Zr) may be included in an amount of 500 ppm to 3,000 ppm based on the total weight of the lithium transition metal composite oxide. As a specific example, the zirconium (Zr) may be included in an amount of 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more based on the total weight of the lithium transition metal composite oxide, and further may be included in an amount of 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

According to one embodiment of the present invention, the M ³ may be included in an amount of 100 ppm to 2,000 ppm based on the total weight of the lithium transition metal composite oxide. As a specific example, the M ³ may be included in an amount of 100 ppm or more, 200 ppm or more, 300 ppm or more, 400 ppm or more, or 500 ppm or more based on the total weight of the lithium transition metal composite oxide, and further may be included in an amount 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.

According to one embodiment of the present invention, the positive electrode active material includes a coating portion formed on at least one of a primary particle surface, a primary particle interface, and a secondary particle surface, and the coating portion may include at least one coating element selected from the group consisting of cobalt (Co) and boron (B).

According to one embodiment of the present invention, the coating portion may be an island-shaped coating portion formed on at least a portion of a primary particle surface, a primary particle interface, and a secondary particle surface.

According to one embodiment of the present invention, the coating portion may be a coating layer formed to surround at least one of a primary particle surface, a primary particle interface, and a secondary particle surface.

According to one embodiment of the present invention, the coating portion may include at least one of a coating portion including cobalt (Co), a coating portion including cobalt (Co) and boron (B), and a coating portion including boron (B).

According to one embodiment of the present invention, the coating portion may include a coating portion in which a coating portion including cobalt (Co), a coating portion including cobalt (Co) and boron (B), and a coating portion including boron (B) are sequentially formed.

According to one embodiment of the present invention, the coating portion may include cobalt-boron oxide.

According to one embodiment of the present invention, when the cathode active material is formed into a pellet by putting the cathode active material into a cylindrical mold having a diameter of 13 mm using an automatic pellet press and applying a force until a force corresponding to 9,000 kgf is reached, the rolling density calculated by Equation 2 below may be 3.60 g/cm ³ or more.

[Formula 2]

Rolling density (g/cm ³ ) = Positive active material weight (g) / Pellet volume (cm ³ )

According to one embodiment of the present invention, the positive electrode active material may have a rolling density calculated by the above formula 2 of 3.60 g/cm ³ or more, and specific examples thereof include 3.61 g/cm ³ or more, 3.62 g/cm ³ or more, 3.63 g/cm ³ or more, 3.64 g/cm ³ or more, 3.65 g/cm ³ or more, 3.66 g/cm ³ or more, 3.67 g/cm ³ or more, 3.68 g/cm ³ or more, 3.69 g/cm ³ or more, 3.70 g/cm ³ or more, or 3.71 g/cm ³ or more, and the upper limit is not particularly limited, but may be 10.0 g/cm ³ or less.

According to one embodiment of the present invention, the positive electrode active material may be such that, for a lithium secondary battery including a positive electrode including the positive electrode active material; an anode; and a separator and an electrolyte interposed between the positive electrode and the anode, when the lithium secondary battery is charged with a 0.5 C current and then discharged with a 0.1 C current, a discharge capacity may be 92.0% or more based on the discharge capacity when the lithium secondary battery is charged with a 0.5 C current and then discharged with a 1.0 C current. Here, the lithium secondary battery is to confirm the discharge capacity according to the output characteristics of the positive electrode active material, and 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 cathode 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 0.5 C current and then discharged with a 0.1 C current, and the upper limit is not particularly limited, but may be 100% or less.

According to one embodiment of the present invention, the positive electrode active material may be such that, for a lithium secondary battery including a positive electrode including the positive electrode active material; an anode; and a separator and an electrolyte interposed between the positive electrode and the anode, when the lithium secondary battery is charged with a 0.5 C current and then discharged with a 0.1 C current, a discharge capacity may be 89.0% or more when the lithium secondary battery is charged with a 0.5 C current and then discharged with a 2.0 C current based on the discharge capacity. Here, the lithium secondary battery is to confirm the discharge capacity according to the output characteristics of the positive electrode active material, and 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 cathode 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, based on the discharge capacity when the lithium secondary battery is charged with a 0.5 C current and then discharged with a 0.1 C current, and the upper limit is not particularly limited, but may be 100% or less.

According to one embodiment of the present invention, the cathode active material may have a single particle size (Dv 50 ), which corresponds to the diameter of the volume at a point where 50% of the cumulative volume distribution of the primary particles is calculated from Equation 5 below for each of the primary particles observed from a SEM image (measurement magnification 3,000 _times ) of the surface of the secondary particles, of 1.2 ㎛ or more and 3.8 ㎛ or less.

[Formula 5]

In the above equation 5,

The radius is the radius of the surface of the primary particle assuming that the surface of the primary particle is circular as observed from the SEM image (measurement magnification 3,000x) of the surface of the secondary particle.

As a specific example, the cathode active material may have a particle size (Dv ₅₀ ) of 1.2 ㎛ or more, 1.3 ㎛ or more, 1.4 ㎛ or more, 1.5 ㎛ or more, 1.6 ㎛ or more, or 1.65 ㎛ or more, and may also have a particle size of 3.8 ㎛ or less, 3.7 ㎛ or less, 3.6 ㎛ or less, 3.59 ㎛ or less, 3.58 ㎛ or less, 3.57 ㎛ or less, 3.56 ㎛ or less, or 3.55 ㎛ or less.

Method for manufacturing positive electrode active material

The present invention provides a method for manufacturing a positive electrode active material.

According to one embodiment of the present invention, the method for manufacturing the positive electrode active material may be a method for manufacturing the positive electrode active material described above.

According to one embodiment of the present invention, the method for manufacturing the cathode active material may be performed including a step (S10) of mixing a cathode active material precursor including nickel, cobalt, and manganese and a lithium raw material, and performing firing to manufacture a sintered product.

According to one embodiment of the present invention, the step (S10) may be performed by a method such as a method of performing firing by dividing temperature sections within one firing step (one-step method), a method of performing firing by dividing two firing steps (two-step method), and a method of performing plastic firing prior to performing firing by dividing temperature sections within one firing step (plastic firing method).

According to one embodiment of the present invention, the one-step method is a method of sequentially performing firing at two temperature sections within one firing step, wherein a single-step firing is performed on a mixture of a positive electrode active material precursor and a lithium raw material, and immediately thereafter, a second-step firing is performed by changing the temperature section. At this time, the two-step firing can be performed at a lower temperature than the single-step firing, and each firing temperature can be controlled according to the nickel content, and through such temperature control, the shape and size of the primary particles and the average particle diameter of the secondary particles can be controlled.

According to one embodiment of the present invention, the two-step method is a method that performs the first firing and the second firing separately, and may be performed by performing the first firing on a mixture of a positive electrode active material precursor and a lithium raw material, pulverizing a first fired product manufactured by the first firing, and then performing the second firing on the pulverized product. At this time, the second firing may be performed at a lower temperature than the first firing, and each firing temperature may be controlled according to the nickel content, and through such temperature control, the shape and size of the primary particles and the average particle diameter of the secondary particles may be controlled.

According to one embodiment of the present invention, the plasticizing method is a method of performing plasticizing prior to one-step sintering, wherein plasticizing is performed on a mixture of a positive electrode active material precursor and a lithium raw material, and the one-step method can be performed on the sintered product. At this time, the plasticizing can be performed at a lower temperature than the one-step sintering, and each sintering temperature can be controlled according to the nickel content, and through such temperature control, the shape and size of the primary particles and the average particle diameter of the secondary particles can be controlled.

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

[Chemical Formula 3]

Ni _a' Co _b' Mn _c'( OH) ₂

In the above chemical formula 3, 0.6≤a'<1.0, 0<b'<0.4, 0<c'<0.4, a'+b'+c'=1.

According to one embodiment of the present invention, in the chemical formula 3, a', b', and c' may be mole fractions of nickel (Ni), cobalt (Co), and manganese (Mn) among transition metals, respectively. As a specific example, a' may be a mole fraction of nickel (Ni) among 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 further may be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. In addition, the b' may be a mole fraction of cobalt (Co) among the transition metals, greater than 0, 0.01, 0.02, or 0.03, and further may 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. The c' may be a mole fraction of manganese (Mn) among the transition metals, greater than 0, 0.01 or more, or 0.05 or more, and further may 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.

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, and for example, Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH H ₂ O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ COOLi, Li ₂ O, Li ₂ SO ₄ , CH ₃ COOLi, Li ₃ C ₆ H ₅ O ₇ or a mixture thereof.

According to one embodiment of the present invention, the step (S10) may be performed by further including one or more doping raw 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 raw material may be an acetate, a nitrate, a sulfate, a halide, a sulfide, a hydroxide, an oxide, or an oxyhydroxide containing the element, and specific examples thereof include Al ₂ O ₃ , Al(OH) ₃ , Al(NO ₃ ) ₃ ·9H ₂ O, Al ₂ (SO ₄ ) ₃ , Y ₂ O ₃ ,It could be ZrO _2, etc.

According to one embodiment of the present invention, the doping raw material may include Al, Y, and Zr. In addition, the doping raw material may include Al, Zr, and a metal element (M ³ ) having an oxidation number of +4 or higher.

According to one embodiment of the present invention, when mixing the positive electrode active material precursor and the lithium raw material in the step (S10), the molar ratio (Li/M) of lithium (Li) of the lithium raw material to the transition metal (M) of the positive electrode active material precursor may be 0.9 or more and 1.3 or less. As a specific example, the Li/M may be 0.9 or more, 0.95 or more, or 1.0 or more, and further may be 1.1 or less, 1.07 or less, 1.05 or less, or 1.04 or less, and the Li/M may be adjusted depending on the content of nickel in the transition metal.

According to one embodiment of the present invention, the method for manufacturing the positive electrode active material may further include a step (S20) of coating the positive electrode active material manufactured in the step (S10). As a specific example, the step (S20) may be performed by including at least one coating raw material selected from the group consisting of Co and B. In addition, the step (S20) may be performed by further including an Al coating raw material.

According to one embodiment of the present invention, the coating of the step (S20) may be performed by coating each coating raw material simultaneously, or may be performed sequentially and separately. As a specific example, the coating of the step (S20) may be performed including a step (S21) of mixing a Co coating raw material and an Al coating raw material into a positive active material and performing heat treatment, and a step (S22) of mixing a B coating raw material into a coating product manufactured in the step (S21) and performing heat treatment.

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 .

According to one embodiment of the present invention, the method for manufacturing the positive electrode active material may include, when performing steps (S10) and (S20), a step of crushing the sintered product after the firing, if necessary, and the crushing may be performed without particular limitation using a crushing device capable of crushing the positive electrode active material.

According to one embodiment of the present invention, the doping raw material and the coating raw material can be introduced by adjusting them to satisfy the doping element content and the coating element content of the positive electrode active material described above.

anode

The present invention provides a positive electrode comprising 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.

According to one embodiment of the present invention, the positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to a positive electrode active material layer but does not react in the voltage range of the battery. The positive electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

According to one embodiment of the present invention, the positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

According to one embodiment of the present invention, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any conductive material that does not cause a chemical change and has electronic conductivity can be used without special limitations. Specific examples thereof 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 or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% with respect to the total weight of the positive electrode active material layer.

According to one embodiment of the present invention, the binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

According to one embodiment of the present invention, the positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent as needed, onto a positive electrode current collector, and then drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, and then peeling off the support to obtain a film and laminating it onto a positive electrode current collector.

According to one embodiment of the present invention, the solvent may be a solvent generally used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these may be used alone or as a mixture of two or more thereof. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity during subsequent coating for manufacturing the positive electrode.

Lithium secondary 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 the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode, and an electrolyte. In addition, the lithium secondary battery may optionally further include a battery container that accommodates an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

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 positioned 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 has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and, like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

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

According to one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples thereof 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 alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium such as SiOβ(0<β<2), _SnO2 , vanadium oxide, and lithium vanadium oxide; or composites including the metallic compounds and carbonaceous materials such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbon material. Representative examples of low-crystallization carbon include soft carbon and hard carbon, and representative examples of high-crystallization carbon include amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, mesophase pitches, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. The negative electrode active material may be included in an amount of 80 to 99 wt% based on the total weight of the negative electrode active material layer.

According to one embodiment of the present invention, the binder of 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 typically added in an amount of 0.1 to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, various copolymers thereof, and the like.

According to one embodiment of the present invention, the conductive material of 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 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. may be used.

According to one embodiment of the present invention, the negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer, which is manufactured by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support and then laminating the resulting film on a negative electrode current collector by peeling it off from the support.

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. If it is a separator that is usually used as a separator in a lithium secondary battery, it can be used without any special limitation, and in particular, it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can be selectively used in a single-layer or multi-layer structure.

According to one embodiment of the present invention, the electrolyte may include, but is not limited to, 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, etc. that can be used in the manufacture of a lithium secondary battery. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

According to one embodiment of the present invention, as the organic solvent, any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move can be used without particular limitation. Specifically, the organic solvent may 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; Examples of solvents that can be used include carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge/discharge performance of the battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

According to one embodiment of the present invention, the lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt may be at least one selected from the group consisting of F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , and the lithium salt may be at least one selected from the group consisting of LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ can be used. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further contain one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, a cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, a nitrobenzene derivative, sulfur, a quinone imine dye, an N-substituted oxazolidinone, an N,N-substituted imidazolidine, ethylene glycol dialkyl ether, an ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additive may be contained in an amount of 0.1 wt% to 5 wt% with respect to the total weight of the electrolyte.

A lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be in the shape of a cylinder, a square, a pouch, or a coin using a can.

The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

Accordingly, 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-sized devices, such as a power tool; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

실시예 및 비교예Examples and Comparative Examples

실시예 1Example 1

A transition metal composite hydroxide (D ₅₀ : 10.2 ㎛) having a composition represented by Ni _0.89 Co _0.03 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.04. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was calcined under 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 produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.8833 Co _0.0298 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

A mixture was prepared by adding the lithium transition metal oxide in the form of secondary particles prepared above and Al(OH) ₃ in an amount of 500 ppm based on the total weight of the lithium transition metal oxide in the form of secondary particles prepared above so that the molar ratio of cobalt (Co) to the metal (Ni+Co+Mn+Al+Y+Zr) excluding _lithium (Co/(Ni+Co+Mn+Al+Y+Zr)) was 0.02, and mixing them uniformly. The mixture was heat-treated at 740°C for 3 hours and then at 500°C for 3 hours in an oxygen atmosphere to obtain a first coated product. The first coated product was pulverized at room temperature to an average particle size ( _D50 ) of 10.2 μm to prepare a cathode active material in which a coating portion including Co and Al was formed on the lithium transition metal oxide in the form of secondary particles in which the primary particles were aggregated. The overall composition of the cathode active material including the above coating portion was LiNi _0.8641 Co _0.0491 Mn _0.0777 Al _0.0066 Y _0.0010 Zr _0.0015 O ₂ .

To the above-mentioned pulverized first coating product, _H3BO3 was added in an amount of 500 _ppm based on the total weight of the above-mentioned pulverized first coating product, and the mixture was mixed to prepare a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coating product. The second coating product was pulverized at room temperature to an average particle diameter ( _D50 ) of 10.2 μm, and a positive electrode active material was prepared in which a coating portion including Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. 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 Y _0.0010 Zr _0.0015 B _0.0045 O ₂ .

실시예 2Example 2

A transition metal composite hydroxide (D ₅₀ : 10.2 μm) having a composition represented by Ni _0.89 Co _0.03 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.00. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was first fired at 850° C. for 6 hours under an oxygen atmosphere to obtain a first fired product. Thereafter, the first fired product was pulverized at room temperature so that the average particle size (D ₅₀ ) became 9.8 μm.

The above-mentioned pulverized primary sintered product and LiOH were mixed so that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li/(Ni+Co+Mn)) was 0.04, and the second sintering was performed at 800° C. for 9 hours in an oxygen atmosphere to obtain a second sintered product. The second sintered product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size ( _D50 ) of 9.8 μm and a composition represented by LiNi _0.8833 Co _0.0298 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles were aggregated.

실시예 3Example 3

The above mixture was calcined at 550°C for 5 hours under an oxygen atmosphere to obtain a calcined product. Thereafter, the calcined product was pulverized at room temperature to an average particle size ( _D50 ) of 9.8 μm.

The above-mentioned pulverized sintered product was calcined in an oxygen atmosphere at 850° C. for 6 hours and then at 800° C. for 9 hours to obtain a sintered product. The sintered product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.8833 Co _0.0298 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

실시예 4Example 4

The above mixture was calcined under an oxygen atmosphere at 880° C. for 6 hours and then at 800° C. for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.8833 Co _0.0298 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

실시예 5Example 5

A transition metal composite hydroxide (D ₅₀ : 10.2 ㎛) having a composition represented by Ni _0.89 Co _0.03 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.04. To this, 1,470 ppm of Al (OH) ₃ , 2,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was calcined under 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 produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.8824 Co _0.0297 Mn _0.0793 Al _0.0050 Y _0.0021 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

A mixture was prepared by adding the lithium transition metal oxide in the form of secondary particles prepared above and Al(OH) ₃ in an amount of 500 ppm based on the total weight of the lithium transition metal oxide in the form of secondary particles prepared above so that the molar ratio of cobalt (Co) to the metal (Ni+Co+Mn+Al+Y+Zr) excluding _lithium (Co/(Ni+Co+Mn+Al+Y+Zr)) was 0.02, and mixing them uniformly. The mixture was heat-treated at 740°C for 3 hours and then at 500°C for 3 hours in an oxygen atmosphere to obtain a first coated product. The first coated product was pulverized at room temperature to an average particle size ( _D50 ) of 10.2 μm to prepare a cathode active material in which a coating portion including Co and Al was formed on the lithium transition metal oxide in the form of secondary particles in which the primary particles were aggregated. The overall composition of the cathode active material including the above coating portion was LiNi _0.8632 Co _0.0491 Mn _0.0776 Al _0.0066 Y _0.0020 Zr _0.0015 O ₂ .

To the above-mentioned pulverized first coating product, _H3BO3 was added in an amount of 500 _ppm based on the total weight of the above-mentioned pulverized first coating product, and the mixture was mixed to prepare a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coating product. The second coating product was pulverized at room temperature to an average particle diameter ( _D50 ) of 10.2 μm, and a positive electrode active material was prepared in which a coating portion including Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the positive electrode active material including the coating portion was LiNi _0.8593 Co _0.0489 Mn _0.0772 Al _0.0066 Y _0.0020 Zr _0.0015 B _0.0045 O ₂ .

실시예 6Example 6

A transition metal composite hydroxide (D ₅₀ : 10.2 μm) having a composition represented by Ni _0.89 Co _0.03 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed 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 in an amount of 2,940 ppm, Y ₂ O ₃ in an amount of 1,000 ppm, and ZrO ₂ in an amount of 1,500 ppm relative to the total weight of the transition metal composite hydroxide, and then mixed to prepare a mixture.

The above mixture was calcined under 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 produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.8789 Co _0.0296 Mn _0.0790 Al _0.0100 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

A mixture was prepared by adding the lithium transition metal oxide in the form of secondary particles prepared above and Al(OH) ₃ in an amount of 500 ppm based on the total weight of the lithium transition metal oxide in the form of secondary particles prepared above so that the molar ratio of cobalt (Co) to the metal (Ni+Co+Mn+Al+Y+Zr) excluding _lithium (Co/(Ni+Co+Mn+Al+Y+Zr)) was 0.02, and mixing them uniformly. The mixture was heat-treated at 740°C for 3 hours and then at 500°C for 3 hours in an oxygen atmosphere to obtain a first coated product. The first coated product was pulverized at room temperature to an average particle size ( _D50 ) of 10.2 μm to prepare a cathode active material in which a coating portion including Co and Al was formed on the lithium transition metal oxide in the form of secondary particles in which the primary particles were aggregated. The overall composition of the positive electrode active material including the above coating portion was LiNi _0.8597 Co _0.0490 Mn _0.0773 Al _0.0115 Y _0.0010 Zr _0.0015 O ₂ .

To the above-mentioned pulverized first coating product, _H3BO3 was added in an amount of 500 _ppm based on the total weight of the above-mentioned pulverized first coating product, and the mixture was mixed to prepare a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coating product. The second coating product was pulverized at room temperature to an average particle diameter ( _D50 ) of 10.2 μm, and a positive electrode active material was prepared in which a coating portion including Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the positive electrode active material including the coating portion was LiNi _0.8559 Co _0.0488 Mn _0.0769 Al _0.0115 Y _0.0010 Zr _0.0014 B _0.0045 O ₂ .

실시예 7Example 7

A transition metal composite hydroxide (D ₅₀ : 10.2 ㎛) having a composition represented by Ni _0.89 Co _0.03 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.04. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 3,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was calcined under 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 produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.8815 Co _0.0297 Mn _0.0793 Al _0.0050 Y _0.0010 Zr _0.0035 O ₂ in the form of secondary particles in which primary particles are aggregated.

A mixture was prepared by adding the lithium transition metal oxide in the form of secondary particles prepared above and Al(OH) ₃ in an amount of 500 ppm based on the total weight of the lithium transition metal oxide in the form of secondary particles prepared above so that the molar ratio of cobalt (Co) to the metal (Ni+Co+Mn+Al+Y+Zr) excluding _lithium (Co/(Ni+Co+Mn+Al+Y+Zr)) was 0.02, and mixing them uniformly. The mixture was heat-treated at 740°C for 3 hours and then at 500°C for 3 hours in an oxygen atmosphere to obtain a first coated product. The first coated product was pulverized at room temperature to an average particle size ( _D50 ) of 10.2 μm to prepare a cathode active material in which a coating portion including Co and Al was formed on the lithium transition metal oxide in the form of secondary particles in which the primary particles were aggregated. The overall composition of the cathode active material including the above coating portion was LiNi _0.8623 Co _0.0491 Mn _0.0775 Al _0.0066 Y _0.0010 Zr _0.0035 O ₂ .

To the above-mentioned pulverized first coating product, _H3BO3 was added in an amount of 500 _ppm based on the total weight of the above-mentioned pulverized first coating product, and the mixture was mixed to prepare a mixture. The mixture was heat-treated at 330°C for 5 hours in an air atmosphere to obtain a second coating product. The second coating product was pulverized at room temperature to an average particle diameter ( _D50 ) of 10.2 μm, and a positive electrode active material was prepared in which a coating portion including Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the positive electrode active material including the coating portion was LiNi _0.8584 Co _0.0489 Mn _0.0772 Al _0.0066 Y _0.0010 Zr _0.0034 B _0.0045 O ₂ .

실시예 8Example 8

A transition metal composite hydroxide (D ₅₀ : 14.5 μm) having a composition represented by Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.02. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was calcined under an oxygen atmosphere at 800° C. for 6 hours and then at 760° C. for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 14.2 μm and a composition represented by LiNi _0.9528 Co _0.0298 Mn _0.0099 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

A mixture was prepared by adding the lithium transition metal oxide in the form of secondary particles prepared above and Al(OH) ₃ in an amount of 500 ppm based on the total weight of the lithium transition metal oxide in the form of secondary particles prepared above so that the molar ratio of cobalt (Co) to the metal (Ni+Co+Mn+Al+Y+Zr) excluding _lithium (Co/(Ni+Co+Mn+Al+Y+Zr)) was 0.02, and mixing them uniformly. The mixture was heat-treated at 700°C for 3 hours and then at 500°C for 3 hours in an oxygen atmosphere to obtain a first coated product. The first coated product was pulverized at room temperature to an average particle size ( _D50 ) of 14.5 μm to prepare a positive electrode active material in which a coating portion including Co and Al was formed on the lithium transition metal oxide in the form of secondary particles in which the primary particles were aggregated. The overall composition of the positive electrode active material including the above coating portion was LiNi _0.9320 Co _0.0491 Mn _0.0097 Al _0.0067 Y _0.0010 Zr _0.0015 O ₂ .

To the above-mentioned pulverized first coating product, _H3BO3 was added in an amount of 500 _ppm based on the total weight of the above-mentioned pulverized first coating product, and the mixture was mixed to prepare a mixture. The mixture was heat-treated at 330° C. for 5 hours in an air atmosphere to obtain a second coating product. The second coating product was pulverized at room temperature to an average particle diameter ( _D50 ) of 14.2 μm, and a positive electrode active material was prepared in which a coating portion including Co, Al, and B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the positive electrode active material including the coating portion was LiNi _0.9278 Co _0.0489 Mn _0.0097 Al _0.0066 Y _0.0010 Zr _0.0015 B _0.0045 O ₂ .

실시예 9Example 9

A transition metal composite hydroxide (D ₅₀ : 14.5 ㎛) having a composition represented by Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 0.98. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was first fired at 800° C. for 6 hours under an oxygen atmosphere to obtain a first fired product. Thereafter, the first fired product was pulverized at room temperature so that the average particle size (D ₅₀ ) became 14.2 μm.

The above-mentioned pulverized primary sintered product and LiOH were mixed so that the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li/(Ni+Co+Mn)) was 0.04, and the second sintering was performed at 760°C for 9 hours in an oxygen atmosphere to obtain a second sintered product. The second sintered product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size ( _D50 ) of 14.2 μm and a composition represented by LiNi _0.9528 Co _0.0298 Mn _0.0099 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles were aggregated.

실시예 10Example 10

The above mixture was calcined at 550°C for 5 hours under an oxygen atmosphere to obtain a calcined product. Thereafter, the calcined product was pulverized at room temperature to an average particle size ( _D50 ) of 14.2 μm.

The above-mentioned pulverized sintered product was calcined in an oxygen atmosphere at 800° C. for 6 hours and then at 760° C. for 9 hours to obtain a sintered product. The sintered product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 14.2 μm and a composition represented by LiNi _0.9528 Co _0.0298 Mn _0.0099 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

실시예 11Example 11

The above mixture was calcined under an oxygen atmosphere at 830° C. for 6 hours and then at 760° C. for 9 hours to obtain a calcined product. The calcined product was pulverized at room temperature to produce a lithium transition metal oxide having an average particle size (D ₅₀ ) of 14.2 μm and a composition represented by LiNi _0.9528 Co _0.0298 Mn _0.0099 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated.

비교예 1Comparative Example 1

A transition metal composite hydroxide (D ₅₀ : 10.2 ㎛) having a composition represented by Ni _0.87 Co _0.05 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.05. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was fired at 780° C. for 5 hours under an oxygen atmosphere to obtain a fired product. The fired product was pulverized at room temperature to prepare a lithium transition metal oxide having an average particle size ( _D50 ) of 9.8 μm and a composition represented by LiNi _0.8635 Co _0.0496 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles were aggregated. Subsequently, 100 parts by weight of the above-mentioned lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed using a filter press. The washed product was dried at 130° C. for 4 hours to prepare a dried product.

To the above-mentioned manufactured dry product, H ₃ BO ₃ was added in an amount of 1,000 ppm based on the total weight of the lithium transition metal oxide, and the mixture was prepared. The mixture was heat-treated at 300 ℃ for 5 hours in an air atmosphere to obtain a coating product. The coated product was pulverized at room temperature to have an average particle diameter (D ₅₀ ) of 10.2 ㎛, thereby preparing a cathode active material in which a coating portion including B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the cathode 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 O ₂ .

비교예 2Comparative Example 2

A transition metal composite hydroxide (D ₅₀ : 12.2 μm) having a composition represented by Ni _0.87 Co _0.05 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.05. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was fired at 780° C. for 5 hours under an oxygen atmosphere to obtain a fired product. The fired product was pulverized at room temperature to prepare a lithium transition metal oxide having an average particle size (D ₅₀ ) of 11.8 μm and a composition represented by LiNi _0.8635 Co _0.0496 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles were aggregated. Subsequently, 100 parts by weight of the above-mentioned lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed using a filter press. The washed product was dried at 130° C. for 4 hours to prepare a dried product.

To the above-mentioned manufactured dry product, H ₃ BO ₃ was added in an amount of 1,000 ppm based on the total weight of the lithium transition metal oxide, and the mixture was prepared. The mixture was heat-treated at 300 ℃ for 5 hours in an air atmosphere to obtain a coating product. The coated product was pulverized at room temperature to have an average particle diameter (D ₅₀ ) of 12.2 ㎛, thereby preparing a cathode active material in which a coating portion including B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the cathode 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 O ₂ .

비교예 3Comparative Example 3

A transition metal composite hydroxide (D ₅₀ : 14.5 μm) having a composition represented by Ni _0.94 Co _0.05 Mn _0.01 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.02. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above 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 ( _D50 ) of 14.2 μm. A lithium transition metal oxide having a composition represented by LiNi _0.9330 Co _0.0496 Mn _0.0099 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles are aggregated was manufactured. Subsequently, 100 parts by weight of the manufactured lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed using a filter press. The washed product was dried at 130°C for 4 hours to manufacture a dried product.

To the above-mentioned manufactured dry product, H ₃ BO ₃ was added in an amount of 1,000 ppm based on the total weight of the lithium transition metal oxide, and the mixture was prepared. The mixture was heat-treated at 300 ℃ for 5 hours in an air atmosphere to obtain a coating product. The coated product was pulverized at room temperature to have an average particle diameter (D ₅₀ ) of 14.2 ㎛, thereby preparing a cathode active material in which a coating portion including B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the cathode 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 O ₂ .

비교예 4Comparative Example 4

A transition metal composite hydroxide (D ₅₀ : 10.2 μm) having a composition represented by Ni _0.94 Co _0.05 Mn _0.01 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.02. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was fired at 730° C. for 5 hours under an oxygen atmosphere to obtain a fired product. The fired product was pulverized at room temperature to prepare a lithium transition metal oxide having an average particle size (D ₅₀ ) of 9.8 μm and a composition represented by LiNi _0.9330 Co _0.0496 Mn _0.0099 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ in the form of secondary particles in which primary particles were aggregated. Subsequently, 100 parts by weight of the above-mentioned lithium transition metal oxide in the form of secondary particles and 100 parts by weight of water were stirred for 5 minutes, and then washed using a filter press. The washed product was dried at 130° C. for 4 hours to prepare a dried product.

To the above-mentioned manufactured dry product, H ₃ BO ₃ was added in an amount of 1,000 ppm based on the total weight of the lithium transition metal oxide, and the mixture was prepared. The mixture was heat-treated at 300 ℃ for 5 hours in an air atmosphere to obtain a coating product. The coated product was pulverized at room temperature to have an average particle diameter (D ₅₀ ) of 10.2 ㎛, thereby preparing a cathode active material in which a coating portion including B was formed on a lithium transition metal oxide in the form of secondary particles in which primary particles were aggregated. The total composition of the cathode 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 O ₂ .

비교예 5Comparative Example 5

A transition metal composite hydroxide (D ₅₀ : 4.2 ㎛) having a composition represented by Ni _0.89 Co _0.03 Mn _0.08 (OH) ₂ in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles and LiOH were mixed such that the molar ratio of lithium (Li) to transition metal (Ni + Co + Mn) (Li / (Ni + Co + Mn)) was 1.04. To this, 1,470 ppm of Al (OH) ₃ , 1,000 ppm of Y ₂ O ₃ , and 1,500 ppm of ZrO ₂ were added and mixed relative to the total weight of the transition metal composite hydroxide to prepare a mixture.

The above mixture was calcined under an oxygen atmosphere at 930° C. for 6 hours and then at 830° C. for 9 hours to obtain a sintered product. The sintered product was pulverized at room temperature to produce a lithium transition metal oxide in the form of single particles having an average particle size (D ₅₀ ) of 3.8 μm and a composition represented by LiNi _0.8833 Co _0.0298 Mn _0.0794 Al _0.0050 Y _0.0010 Zr _0.0015 O ₂ .

A mixture was prepared by adding the lithium transition metal oxide in the form of single particles prepared above and Al(OH) ₃ in an amount of 500 ppm based on the total weight of the lithium transition metal oxide in the form of single particles prepared above so that the molar ratio of cobalt (Co) to the metal (Ni+Co+Mn+Al+Y+Zr) excluding lithium (Co/(Ni+Co+Mn+Al+Y+Zr)) was 0.02, and mixing them uniformly. The mixture was heat-treated at 740°C for 3 hours and then at 500°C for ₃ hours in an oxygen atmosphere to obtain a coating product. The coated product was pulverized at room temperature to an average particle size ( _D50 ) of 3.8 μm, thereby preparing a cathode active material in which a coating portion including Co and Al was formed on the lithium transition metal oxide in the form of single particles. The overall composition of the cathode active material including the above coating portion was LiNi _0.8641 Co _0.0491 Mn _0.0777 Al _0.0066 Y _0.0010 Zr _0.0015 O ₂ .

실험예Experimental example

실험예 1: 입자 분석 1Experimental Example 1: Particle Analysis 1

The positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5 were each photographed using a scanning electron microscope (FEI quanta 250 FEG), and the SEM images of Examples 1 to 11 are respectively shown in (A) of FIGS. 1 to 11 in that order, and the SEM images of Comparative Examples 1 to 5 are respectively shown in (A) of FIGS. 12 to 16 in that order. From the SEM images, the average particle size of the primary particles present in each of the Examples and Comparative Examples was measured, and is shown in Table 1 below.

And, after ion milling each of the positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5, images were taken using a scanning electron microscope, and the SEM images of Examples 1 to 11 are sequentially shown in Figs. 1 to 11 (B), respectively, and the SEM images of Comparative Examples 1 to 5 are sequentially shown in Figs. 12 to 16 (B), respectively. The white squares in Figs. 1 to 15 (B) represent SEM images of cross-sections of secondary particles observed from SEM images of cross-sections of secondary particles photographed for cross-sections of the positive electrode active materials, in which the size of the cross-section of the secondary particles is within the range of the average particle diameter (D ₅₀ ) of the secondary particles, by setting a unit area of 5 ㎛ width x 5 ㎛ height within the cross-section of the secondary particles, and the number of cross-sections of the primary particles confirmed within the unit area is shown in Table 1 below.

In addition, a segmentation image showing multiple lithium composite transition metal oxides segmented by performing image analysis based on an artificial intelligence model from the SEM image of Example 1 of the present invention is shown in FIG. 17, and a segmentation image of Comparative Example 1 is shown in FIG. 18.

구분division	SEM 이미지로부터 측정한 1차 입자의 평균 입자 크기 (㎛)Average particle size (㎛) of primary particles measured from SEM images	단위 면적 내 1차 입자의 단면의 개수Number of cross sections of primary particles per unit area
실시예 1Example 1	2.52.5	1313
실시예 2Example 2	2.72.7	1818
실시예 3Example 3	2.82.8	2222
실시예 4Example 4	3.23.2	1010
실시예 5Example 5	2.62.6	88
실시예 6Example 6	2.42.4	1515
실시예 7Example 7	2.62.6	1111
실시예 8Example 8	1.71.7	1313
실시예 9Example 9	1.81.8	1414
실시예 10Example 10	1.91.9	2424
실시예 11Example 11	2.12.1	1919
비교예 1Comparative Example 1	< 0.5< 0.5	120120
비교예 2Comparative Example 2	< 0.5< 0.5	161161
비교예 3Comparative Example 3	< 0.5< 0.5	145145
비교예 4Comparative Example 4	< 0.5< 0.5	127127
비교예 5Comparative Example 5	4.04.0	--

실험예 2: 입자 분석 2Experimental Example 2: Particle Analysis 2

The positive electrode active materials manufactured in Examples 1, 2, and 8 were each subjected to ion milling, and then photographed using a transmission electron microscope (FEI Titan cubed G2 60-300). TEM images of cross-sections of primary particles of the positive electrode active materials of Examples 1, 2, and 8 are shown in FIGS. 19 to 21, respectively.

Referring to FIGS. 1 to 11 and Table 1, in the case of the positive electrode active materials of Examples 1 to 11, it can be confirmed that a plurality of primary particles include aggregated secondary particles, and that the plurality of primary particles have an average particle size of 1.5 ㎛ or more and 5.0 ㎛ or less as measured from an SEM image. In addition, it can be confirmed that the plurality of primary particles include three or more disk-type primary particles. At this time, the disk-type primary particle means a primary particle in which, when two imaginary tangent lines are drawn for two boundaries of primary particles existing within an angle of 45° or less with respect to the major axis direction among the primary particles observed from an SEM image of the surface or cross-section of the secondary particle, the imaginary tangent lines having the largest number of contact points are respectively drawn, and one imaginary line crossing the two tangent lines is drawn, and the same internal angle is 150° or more and 210° or less. For reference, when two virtual yellow tangent lines having the largest number of contact points are drawn for each of the two boundary lines of the primary particles existing within an angle of 45° or less based on the major axis direction in red in (B) of FIGS. 1 to 11, one virtual line (not shown) crossing the two yellow tangent lines satisfies the condition that the same internal angle is 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 ㎛ or more and an aspect ratio (major axis/minor axis) of 1.5 or more. In addition, it can be confirmed that the number of cross-sections of the primary particle per unit area is 1 or more and 100 or less. Specifically, it can be confirmed that the number of cross-sections of the primary particle per unit area is 8 or more and 24 or less.

In addition, referring to FIGS. 1 to 11 and 19 to 21, in the case of the positive electrode active material according to one embodiment of the present invention, it can be confirmed that the area ratio of the (003) plane among the crystal planes on the surface of the primary particle is the largest.

Meanwhile, in the case of the positive electrode active materials of Comparative Examples 1 to 4, it can be confirmed that the average particle size of the primary particles measured from the SEM image is small, less than 500 nm.

And, referring to FIGS. 17 and 18, it can be confirmed that the cathode active material according to one embodiment of the present invention includes single crystal primary particles.

실험예 3: 입자 분석 3Experimental Example 3: Particle Analysis 3

The positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5 were photographed using a scanning electron microscope equipped with EBSD (FEI quanta 250 FEG).

Among these, for the cross-sections of the positive electrode active materials of Examples 1 to 4, 8, 10, 11 and Comparative Example 3, the cross-sections of the secondary particles are observed from the backscattered electron diffraction (EBSD) patterns (measured under the conditions of an acceleration voltage of 20 kV, a WD of 16 mm, a measurement magnification of 5,000 times (width 16 ㎛ * height 16 ㎛), and a step size of 0.025 ㎛) of the SEM images of the cross-sections of the secondary particles, in which the size of the cross-sections of the secondary particles is within the range of the average particle diameter (D ₅₀ ), a unit area of 5 ㎛ in width * 5 ㎛ in height is set in the center region and the outer region, respectively, as shown in FIG. 22 (Example 1), FIG. 23 (Example 2), FIG. 24 (Example 3), FIG. 25 (Example 4), and FIG. 26 (Example 8), FIG. 27 (Example 10), FIG. 28 (Example 11), and FIG. 29 (Comparative Example 3), respectively, and the number of cross-sections of grains confirmed within the unit area and the degree of single crystallinity calculated according to the following Equation 1 are also shown in Table 2 below.

[Formula 1]

구분division	가운데 영역의 단위 면적 내 그레인의 단면의 개수Number of cross-sections of grains within a unit area of the central region	바깥 영역의 단위 면적 내 그레인의 단면의 개수The number of cross-sections of grains within a unit area of the outer region	단결정화도(㎛³)Single crystallinity (㎛ ³ )
실시예 1Example 1	1212	1414	0.860.86
실시예 2Example 2	33	66	0.900.90
실시예 3Example 3	88	99	0.920.92
실시예 4Example 4	66	66	0.980.98
실시예 5Example 5	--	--	0.870.87
실시예 6Example 6	--	--	0.870.87
실시예 7Example 7	--	--	0.880.88
실시예 8Example 8	1212	1919	1.091.09
실시예 9Example 9	--	--	1.201.20
실시예 10Example 10	77	99	1.571.57
실시예 11Example 11	1212	1313	1.561.56
비교예 1Comparative Example 1	--	--	0.0460.046
비교예 2Comparative Example 2	--	--	0.0400.040
비교예 3Comparative Example 3	203203	180180	0.0500.050
비교예 4Comparative Example 4	--	--	0.0700.070
비교예 5Comparative Example 5	--	--	3.13.1

Referring to Table 2, it can be confirmed that, for the positive electrode active materials of Examples 1 to 11, the number of cross-sections of grains per unit area is 1 or more and 150 or less. Specifically, it can be confirmed that the number of cross-sections of grains per unit area is 3 or more and 19 or less. In addition, it can be confirmed that the single crystallinity is 0.15 ㎛ ³ or more. Specifically, it can be confirmed that the single crystallinity is 0.86 ㎛ ³ or more and 1.57 ㎛ ³ or less.

실험예 4: 입자 분석 4Experimental Example 4: Particle Analysis 4

From the SEM images of the positive electrode active materials obtained in the above Experimental Example 1, the single particle diameter (Dv ₅₀ ) corresponding to the diameter of the volume at the point where 50% of the cumulative volume distribution of the primary particles present in each of the examples and comparative examples was measured, and is shown in Table 3 below.

Specifically, the area of each primary particle is measured through the number of pixels corresponding to each of n primary particles observed from an image in which the SEM images of the surfaces of the secondary particles photographed on the surfaces of the positive active materials of Examples 1 to 11 and Comparative Examples 1 to 5 are projected onto a two-dimensional plane. Thereafter, assuming that the surfaces of the primary particles are circular, that is, the radius of the surface of the primary particle was derived using the radius of a circle having the same area as the surface area of each of the primary particles. Using the radius, the volume value was calculated according to Equation 5 below, and the single particle size (Dv ₅₀ ) corresponding to the diameter of the volume at a point where the cumulative volume distribution of the primary particles is 50% was calculated, and the results are shown in Table 3 below.

[Formula 5]

구분division	단입자화도(Dv₅₀) (㎛)Single particle magnetization (Dv ₅₀ ) (㎛)
실시예 1Example 1	2.232.23
실시예 2Example 2	2.242.24
실시예 3Example 3	2.262.26
실시예 4Example 4	3.513.51
실시예 5Example 5	2.342.34
실시예 6Example 6	2.212.21
실시예 7Example 7	2.332.33
실시예 8Example 8	1.691.69
실시예 9Example 9	1.701.70
실시예 10Example 10	1.721.72
실시예 11Example 11	2.832.83
비교예 1Comparative Example 1	1.051.05
비교예 2Comparative Example 2	1.011.01
비교예 3Comparative Example 3	0.800.80
비교예 4Comparative Example 4	0.870.87
비교예 5Comparative Example 5	3.483.48

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

실험예 5: 입자 분석 5Experimental Example 5: Particle Analysis 5

In order to analyze the elemental distribution of the Co and B coating layers present on the surface of the positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 4, electron spectroscopic chemical analysis (ESCA) was performed using a K-alpha XPS device from Thermo Fisher. For depth profiling, etching was performed at a rate of 0.3 nm/10 s using an Ar ion source, and the contents (atomic %) of B and Co, respectively, included in the coating layers having a thickness of 0 to 100 nm were measured, and the results are shown in Tables 4 (B coating layer) and 5 (Co coating layer), respectively.

For the positive electrode active material of Example 1, EPMA cross-sectional analysis was performed to confirm the surface coating characteristics. First, the positive electrode active material of Example 1, carbon black conductive agent, and PVDF binder were mixed at a weight ratio of 95:2:3 in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and rolled so that the electrode porosity became 20% to prepare a positive electrode. In order to create a flat surface for EPMA cross-sectional analysis, the positive electrode was subjected to Ar-ion milling using a HITACHI IM-5000 equipment under an acceleration voltage of 6 kV to obtain a cross-section of the positive electrode sample. Then, the cross-sectional image of the positive electrode sample was observed using a JEOL JXA-iHP200F equipment under the conditions of an acceleration voltage of 15 kV and a probe current of 50 nA, and the results are shown in Fig. 30.

에칭 시간 (s)Etching time (s)	00	1010	3030	5050	100100	200200	300300	500500	10001000	20002000	30003000
실시예 1Example 1	10.410.4	10.710.7	9.49.4	8.48.4	6.66.6	4.34.3	3.43.4	2.42.4	1.61.6	1.31.3	11
실시예 2Example 2	1111	10.810.8	9.49.4	8.18.1	6.56.5	44	3.73.7	2.82.8	1.91.9	1.11.1	11
실시예 3Example 3	10.410.4	10.810.8	9.49.4	8.98.9	6.76.7	4.34.3	3.73.7	2.42.4	1.71.7	1.21.2	11
실시예 4Example 4	10.410.4	10.210.2	9.29.2	99	6.86.8	4.84.8	3.53.5	2.82.8	1.81.8	1.51.5	11
실시예 5Example 5	10.410.4	10.710.7	9.99.9	8.18.1	6.76.7	4.54.5	3.43.4	2.92.9	1.11.1	1.51.5	11
실시예 6Example 6	10.410.4	10.110.1	9.29.2	8.28.2	6.16.1	4.44.4	3.83.8	2.82.8	1.21.2	1.51.5	11
실시예 7Example 7	10.410.4	10.810.8	9.79.7	8.48.4	6.26.2	44	33	2.42.4	1.51.5	1.21.2	11
실시예 8Example 8	11.211.2	11.211.2	9.19.1	8.78.7	6.86.8	4.24.2	3.13.1	2.92.9	1.91.9	1.41.4	11
실시예 9Example 9	10.710.7	10.710.7	9.19.1	8.18.1	6.46.4	4.94.9	33	2.82.8	1.71.7	1.51.5	11
실시예 10Example 10	10.710.7	10.810.8	9.49.4	88	6.46.4	4.24.2	3.43.4	2.52.5	1.81.8	1.51.5	11
실시예 11Example 11	1111	11.211.2	9.29.2	8.78.7	6.16.1	4.54.5	3.73.7	2.92.9	1.91.9	1.51.5	11
비교예 1Comparative Example 1	16.416.4	17.517.5	15.115.1	14.814.8	11.811.8	8.98.9	77	5.95.9	3.53.5	2.42.4	1.51.5
비교예 2Comparative Example 2	1616	17.517.5	14.814.8	14.814.8	1212	8.78.7	7.87.8	5.15.1	33	22	11
비교예 3Comparative Example 3	1616	16.816.8	15.115.1	14.814.8	11.411.4	8.88.8	7.57.5	5.95.9	3.53.5	1.91.9	1.51.5
비교예 4Comparative Example 4	15.415.4	16.416.4	1515	14.814.8	11.211.2	8.78.7	77	5.55.5	3.83.8	22	1.11.1

에칭 시간 (s)Etching time (s)	00	1010	3030	5050	100100	200200	300300	500500	10001000	20002000	30003000
실시예 1Example 1	1.81.8	33	4.54.5	5.45.4	5.95.9	4.84.8	3.93.9	2.22.2	1.11.1	0.90.9	0.80.8
실시예 2Example 2	1.71.7	2.92.9	4.94.9	5.15.1	66	4.54.5	3.83.8	2.12.1	1.21.2	11	11
실시예 3Example 3	1.61.6	2.62.6	4.54.5	5.15.1	6.16.1	4.64.6	3.93.9	22	11	0.70.7	0.70.7
실시예 4Example 4	1.91.9	2.72.7	4.14.1	5.25.2	6.26.2	4.74.7	3.43.4	2.42.4	1.21.2	0.80.8	0.80.8
실시예 5Example 5	1.71.7	2.82.8	4.24.2	5.35.3	5.85.8	4.74.7	44	1.91.9	1.11.1	0.90.9	0.90.9
실시예 6Example 6	22	2.82.8	4.24.2	5.55.5	5.95.9	4.84.8	3.73.7	22	0.90.9	0.70.7	0.80.8
실시예 7Example 7	1.81.8	2.72.7	4.54.5	5.45.4	5.55.5	4.94.9	3.83.8	2.12.1	1.11.1	0.90.9	0.60.6
실시예 8Example 8	1.61.6	33	4.54.5	5.35.3	5.95.9	4.54.5	3.53.5	2.22.2	1.31.3	11	0.70.7
실시예 9Example 9	1.71.7	3.13.1	4.24.2	5.35.3	5.95.9	4.84.8	3.83.8	2.12.1	11	1.11.1	0.90.9
실시예 10Example 10	22	3.13.1	4.44.4	5.15.1	66	4.94.9	3.93.9	22	1.21.2	0.90.9	0.80.8
실시예 11Example 11	1.91.9	3.33.3	4.54.5	5.15.1	6.16.1	4.94.9	44	2.12.1	0.90.9	1.11.1	0.70.7
비교예 1Comparative Example 1	00	0.10.1	0.10.1	0.30.3	0.30.3	0.30.3	0.40.4	0.80.8	0.90.9	0.90.9	0.60.6
비교예 2Comparative Example 2	00	0.10.1	0.20.2	0.30.3	0.20.2	0.40.4	0.50.5	0.70.7	0.80.8	0.60.6	0.50.5
비교예 3Comparative Example 3	0.10.1	0.10.1	0.20.2	0.20.2	0.30.3	0.50.5	0.40.4	0.70.7	0.70.7	0.80.8	1.01.0
비교예 4Comparative Example 4	0.10.1	0.20.2	0.10.1	0.20.2	0.30.3	0.30.3	0.40.4	0.70.7	0.70.7	0.80.8	1.01.0

Referring to the SEM images of FIGS. 1 to 11 and Tables 4, 5 and FIG. 30 above, in the case of the positive electrode active materials of Examples 1 to 11, it can be confirmed that a coating portion including Co and/or B is formed on the surface of the primary particle, the interface of the primary particle and/or the surface of the secondary particle. In addition, it can be confirmed that the coating portion has both an island shape formed on a portion of the surface of the primary particle, the interface of the primary particle and/or the surface of the secondary particle and a coating layer shape formed to surround the surface of the primary particle, the interface of the primary particle and/or the surface of the secondary particle.

실험예 6: 체적 누적 분포 분석Experimental Example 6: Volume cumulative distribution analysis

For the positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5, a particle size analyzer (PSD, Malvern, martersizer 3500) was used to measure D _min , D ₅₀ and D _max , the mode in the cumulative volume distribution according to particle size, the y value of the peak point at the top of the y-axis of the peak appearing in the mode according to the cumulative volume distribution (P _MODE ), θ _L and θ _R , and θ _L - θ _R were calculated, which are shown in Table 6.

And, the skewness value (S) is calculated from the following equation 3, and the ratio (S/P MODE) of the skewness value (S) to the y-value (P _MODE ) of the peak point at the top of the y-axis of the peak appearing in the mode ( _Mode ) according to the cumulative volume distribution is calculated, and these are shown together in Table 6 below.

[Formula 3]

In addition, the volume cumulative distributions of the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 and 3, which were measured using a laser diffraction particle size analyzer, are shown in Figs. 31 (Example 1), 32 (Example 2), 33 (Example 3), 34 (Example 4), 35 (Example 5), 36 (Example 6), 37 (Example 7), 38 (Example 8), 39 (Example 9), 40 (Example 10), 41 (Example 11), 42 (Comparative Example 1), and 43 (Comparative Example 3), respectively, in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

And, the volume cumulative distributions of the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 and 3, which were measured using a laser diffraction particle size analyzer, are plotted in a frequency distribution graph in which the x-axis represents a log scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top, respectively, in FIGS. 44 (Example 1), 45 (Example 2), 46 (Example 3), 47 (Example 4), 48 (Example 5), 49 (Example 6), 50 (Example 7), 51 (Example 8), 52 (Example 9), 53 (Example 10), 54 (Example 11), 55 (Comparative Example 1), and 56 (Comparative Example 3).

구분division	D_min (㎛)D _min (㎛)	D₅₀ (㎛)D ₅₀ (㎛)	D_max (㎛)D _max (㎛)	Mode (㎛)Mode (㎛)	P_MODE P _MODE	왜도값 (S)Skewness value (S)	S/P_MODE S/P _MODE	θ_L θ _L	θ_R θ _R	θ_L/θ_R θ _L/ θ _R	θ_L - θ_R θ _L - θ _R
실시예 1Example 1	2.522.52	11.4711.47	62.2362.23	12.0012.00	8.518.51	0.9260.926	0.1090.109	47.98047.980	33.16133.161	1.4471.447	14.81914.819
실시예 2Example 2	5.045.04	10.3210.32	37.0037.00	10.6010.60	13.7213.72	1.0371.037	0.0760.076	71.68471.684	63.08963.089	1.1361.136	8.5958.595
실시예 3Example 3	4.624.62	9.879.87	37.0037.00	9.929.92	12.9812.98	0.5870.587	0.0450.045	71.21571.215	62.58262.582	1.1381.138	8.6338.633
실시예 4Example 4	3.273.27	10.0610.06	52.3352.33	10.5010.50	12.7512.75	1.0071.007	0.0790.079	50.34550.345	42.75142.751	1.2351.235	7.5947.594
실시예 5Example 5	5.045.04	9.959.95	37.0037.00	10.3710.37	12.2512.25	0.7440.744	0.0610.061	72.13572.135	65.42165.421	1.1031.103	6.7146.714
실시예 6Example 6	5.505.50	10.6210.62	40.3540.35	10.6010.60	13.3213.32	1.0171.017	0.0760.076	72.84272.842	65.9565.95	1.1051.105	6.8926.892
실시예 7Example 7	5.045.04	10.2910.29	37.0037.00	10.0910.09	13.0613.06	0.7610.761	0.0580.058	72.75372.753	65.00565.005	1.1191.119	7.7487.748
실시예 8Example 8	8.488.48	14.0714.07	37.0037.00	14.2714.27	16.4216.42	0.6580.658	0.0400.040	71.52171.521	64.75764.757	1.1041.104	6.7646.764
실시예 9Example 9	8.488.48	14.1314.13	37.0037.00	14.2714.27	16.3116.31	0.8000.800	0.0490.049	70.69570.695	63.29563.295	1.1171.117	7.4007.400
실시예 10Example 10	8.488.48	14.2014.20	37.0037.00	14.2714.27	16.2816.28	0.7810.781	0.0480.048	70.53870.538	62.81262.812	1.1231.123	7.7267.726
실시예 11Example 11	8.488.48	14.2714.27	37.0037.00	14.2714.27	16.3016.30	0.7550.755	0.0460.046	70.77470.774	63.00463.004	1.1231.123	7.7707.770
비교예 1Comparative Example 1	6.546.54	9.859.85	26.1626.16	10.0910.09	16.9016.90	0.5960.596	0.0350.035	75.64675.646	71.02071.020	1.0651.065	4.6264.626
비교예 2Comparative Example 2	7.137.13	11.8211.82	37.0037.00	12.0012.00	14.5214.52	0.4110.411	0.0280.028	78.62178.621	73.02673.026	1.0771.077	5.5955.595
비교예 3Comparative Example 3	5.045.04	9.959.95	37.0037.00	10.3710.37	18.0118.01	0.6530.653	0.0360.036	72.13572.135	70.86070.860	1.0181.018	1.2751.275
비교예 4Comparative Example 4	5.505.50	10.6210.62	40.3540.35	10.6010.60	12.0112.01	1.8251.825	0.1520.152	72.84272.842	68.95268.952	1.0561.056	3.893.89
비교예 5Comparative Example 5	2.002.00	4.304.30	18.0518.05	4.464.46	10.3610.36	0.3250.325	0.0310.031	53.21553.215	24.36024.360	2.1852.185	28.85528.855

Referring to Table 6, it can be confirmed that for the positive electrode active materials of Examples 1 to 11, the D ₅₀ is 7.0 ㎛ or more and 20.0 ㎛ or less. In addition, it can be confirmed that the (θ _L - θ _R ) value is 6 or more and 20 or less. In addition, it can be confirmed that the volume cumulative distribution measured using a laser diffraction particle size analyzer exhibits a positive skewness in a frequency distribution graph in which the x-axis represents a linear scale for particle diameter in which the x-value increases from left to right, and the y-axis represents a weight distribution in which the y-value increases from bottom to top.

Meanwhile, in the case of the positive electrode active material of Comparative Example 5, it can be confirmed that D ₅₀ is small, less than 7.0 ㎛.

실험예 7: 압연 밀도 측정Experimental Example 7: Rolling Density Measurement

Using an automatic pellet press (Auto Pellet Press, Carver, 3887.4), a cylindrical mold was used to adjust the zero point for thickness for a circular pellet holder having a diameter of 13 mm. Then, 3 g each of the positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5 was placed in the circular pellet holder, and a force was applied until a force corresponding to 9,000 kgf was reached, and the thickness of the formed pellet was measured. Then, the pellet volume was calculated using the following Equation 4, and the rolling density was calculated using the following Equation 2, and the results are shown in Table 7 below.

[Formula 4]

Pellet volume (cm ³ ) = π (radius of the circular pellet holder) ² X thickness of the pellet

[Formula 2]

구분division	압연 밀도(g/cm³)Rolling density (g/cm ³ )
실시예 1Example 1	3.673.67
실시예 2Example 2	3.683.68
실시예 3Example 3	3.673.67
실시예 4Example 4	3.693.69
실시예 5Example 5	3.683.68
실시예 6Example 6	3.663.66
실시예 7Example 7	3.693.69
실시예 8Example 8	3.753.75
실시예 9Example 9	3.763.76
실시예 10Example 10	3.743.74
실시예 11Example 11	3.763.76
비교예 1Comparative Example 1	3.273.27
비교예 2Comparative Example 2	3.303.30
비교예 3Comparative Example 3	3.493.49
비교예 4Comparative Example 4	3.463.46
비교예 5Comparative Example 5	3.503.50

Referring to Table 7, it can be confirmed that the rolling density of the positive electrode active materials of Examples 1 to 11 is 3.60 g/cm ³ or higher. Specifically, it can be confirmed that the rolling density is 3.66 g/cm ³ or higher.

실험예 8: BET 비표면적 측정Experimental Example 8: BET Surface Area Measurement

The specific surface area was measured by the nitrogen gas adsorption and desorption method. Specifically, after measuring the weight of an empty cell, 3 g each of the positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5 were taken and pretreated at 130° C. for 3 hours. After measuring the weight of the cell after the pretreatment process, a dewar containing liquid nitrogen was prepared and the cell was fastened. The BET specific surface area was measured from the nitrogen gas adsorption amount using a gas adsorption analyzer (Micromeritics TriStarr II) under a nitrogen atmosphere, and the results are shown in Table 8 below.

구분division	비표면적(m²/g)Specific surface area (m ² /g)
실시예 1Example 1	0.3050.305
실시예 2Example 2	0.2940.294
실시예 3Example 3	0.2400.240
실시예 4Example 4	0.3050.305
실시예 5Example 5	0.3120.312
실시예 6Example 6	0.3220.322
실시예 7Example 7	0.3070.307
실시예 8Example 8	0.3320.332
실시예 9Example 9	0.3280.328
실시예 10Example 10	0.2700.270
실시예 11Example 11	0.3380.338
비교예 1Comparative Example 1	0.5040.504
비교예 2Comparative Example 2	0.5920.592
비교예 3Comparative Example 3	0.6310.631
비교예 4Comparative Example 4	0.7290.729
비교예 5Comparative Example 5	0.7480.748

Referring to Table 8, it can be confirmed that the positive electrode active materials of Examples 1 to 11 have a BET specific surface area of 0.20 m ² /g or more and 0.35 m ² /g or less. Specifically, it can be confirmed that the BET specific surface area is 0.240 m ² /g or more and 0.338 m ² /g or less.

실험예 9: 코인형 반쪽전지 제조 및 충방전 평가Experimental Example 9: Manufacturing of Coin-Type Half-cell and Charge-Discharge Evaluation

A positive electrode slurry was prepared by mixing 95 parts by weight of each of the positive electrode active materials manufactured in Examples 1 to 11 and Comparative Examples 1 to 5, 2 parts by weight of a conductive agent (Denka, FX35), and 3 parts by weight of a binder (KUREHA, KF9709) in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of a 20 ㎛ thick aluminum current collector, and rolled so that the porosity of the positive electrode active material layer became 24% by volume, thereby preparing a positive electrode.

An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case and an electrolyte was injected to manufacture a lithium secondary battery. At this time, the electrolyte was manufactured by dissolving 1 M LiPF ₆ in an organic solvent mixed with ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a volume ratio of 3:3:4.

Using lithium secondary batteries including the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 to 5, which were manufactured above, charging was performed in CC/CV mode at a constant current of 0.1 C at 25°C up to 4.25 V (end current 0.05 C), and then discharging in CC mode until 2.5 V was reached, and the charge capacity and discharge capacity were measured, which are shown in Table 9 below. At this time, 1 C = 200 mA/g was set.

In addition, the manufactured lithium secondary battery was charged in CC/CV mode at 45°C with a constant current of 0.5 C to 4.25 V (end current of 0.05 C), and then discharged in CC mode at a constant current of 1.0 C until 2.5 V, which was considered one cycle, and 50 cycles were repeated. The percentage of the discharge capacity of the 50th cycle to the discharge capacity of the first cycle was defined as the capacity retention rate, which is also shown in Table 9 below.

구분division	충전 용량Charging capacity	방전 용량Discharge capacity	효율Efficiency	직류저항DC resistance	고온(45 ℃) 용량 유지율High temperature (45 ℃) capacity retention rate
구분division	(mAh/g)(mAh/g)	(mAh/g)(mAh/g)	(%)(%)	(Ω)(Ω)	(%)(%)
실시예 1Example 1	233.6233.6	209.0209.0	89.589.5	18.518.5	96.1796.17
실시예 2Example 2	233.4233.4	208.4208.4	89.389.3	20.220.2	96.3096.30
실시예 3Example 3	233.6233.6	207.1207.1	88.788.7	20.420.4	96.9396.93
실시예 4Example 4	231.1231.1	205.8205.8	89.189.1	19.419.4	96.5796.57
실시예 5Example 5	232.6232.6	207.7207.7	89.389.3	18.418.4	95.8095.80
실시예 6Example 6	231.7231.7	208.7208.7	90.190.1	18.218.2	96.2096.20
실시예 7Example 7	232.0232.0	207.9207.9	89.689.6	13.213.2	96.5096.50
실시예 8Example 8	247.9247.9	216.5216.5	87.387.3	29.229.2	93.6793.67
실시예 9Example 9	247.6247.6	216.3216.3	87.387.3	30.230.2	94.0094.00
실시예 10Example 10	247.4247.4	215.1215.1	86.986.9	30.230.2	95.4595.45
실시예 11Example 11	245.9245.9	212.4212.4	86.486.4	30.530.5	94.9294.92
비교예 1Comparative Example 1	232.4232.4	212.1212.1	91.391.3	19.619.6	94.9094.90
비교예 2Comparative Example 2	231.1231.1	211.7211.7	91.691.6	20.420.4	94.5094.50
비교예 3Comparative Example 3	242.6242.6	222.8222.8	91.891.8	24.524.5	95.2095.20
비교예 4Comparative Example 4	242.9242.9	223.4223.4	92.092.0	23.123.1	95.3095.30
비교예 5Comparative Example 5	232.3232.3	198.6198.6	85.585.5	26.026.0	95.0095.00

실험예 10: 고율 방전 용량 평가Experimental Example 10: Evaluation of High-Rate Discharge Capacity

Using the lithium secondary battery manufactured in the above Experimental Example 9, the battery was charged in CC/CV mode at 25°C with a constant current of 0.5 C up to 4.25 V (end current of 0.05 C), and then discharged in CC mode at a constant current of 0.1 C until 2.5 V, and the discharge capacity was measured. In addition, the discharge capacity was measured while charging in CC/CV mode at 0.5 C constant current at 25 ℃ to 4.25 V (end current 0.05 C) and then discharging in CC mode at 1.0 C constant current to 2.5 V, and the discharge capacity was measured while charging in CC/CV mode at 0.5 C constant current at 25 ℃ to 4.25 V (end current 0.05 C) and then discharging in CC mode at 2.0 C constant current to 2.5 V, and the percentage of the discharge capacity at 0.1 C discharge after 0.5 C charge is shown in Table 10 below.

구분division	(1.0 C 방전 용량) / (0.1 C 방전 용량) × 100 (%)(1.0 C discharge capacity) / (0.1 C discharge capacity) × 100 (%)	(2.0 C 방전 용량) / (0.1 C 방전 용량) × 100 (%)(2.0 C discharge capacity) / (0.1 C discharge capacity) × 100 (%)
실시예 1Example 1	92.7792.77	90.6490.64
실시예 2Example 2	92.7292.72	90.6490.64
실시예 3Example 3	92.7092.70	90.4890.48
실시예 4Example 4	92.6692.66	90.4490.44
실시예 5Example 5	92.8292.82	90.4390.43
실시예 6Example 6	92.8592.85	90.5890.58
실시예 7Example 7	92.8392.83	90.6490.64
실시예 8Example 8	93.4393.43	91.0291.02
실시예 9Example 9	93.3893.38	90.9590.95
실시예 10Example 10	93.3593.35	90.8790.87
실시예 11Example 11	93.0493.04	89.7889.78
비교예 1Comparative Example 1	87.4787.47	86.1886.18
비교예 2Comparative Example 2	87.6087.60	86.2886.28
비교예 3Comparative Example 3	90.4490.44	87.6387.63
비교예 4Comparative Example 4	90.8490.84	88.7488.74
비교예 5Comparative Example 5	91.5491.54	89.5789.57

Referring to Tables 9 and 10 above, it can be confirmed that the batteries including the positive electrode active materials of Examples 1 to 11 have large discharge capacity, high efficiency and high temperature capacity retention, low DC resistance, and excellent rate characteristics. In contrast, the batteries including the positive electrode active materials of Comparative Examples 1 to 4 have a problem of poor rate characteristics, and the batteries including the positive electrode active material of Comparative Example 5 have a problem of small discharge capacity, low efficiency, and poor rate characteristics.

From these results, it was confirmed that the cathode active material of the present invention can simultaneously solve the problems of the conventional secondary particles and the problems of single particles in high nickel (High Ni) cathode active materials, and by implementing the cathode active material in the form of secondary particles whose primary particles are on the micron level in size, it can not only improve cell characteristics such as improved lifespan and reduced gas generation of lithium secondary batteries, but also improve energy density due to excellent density characteristics.

Claims

Contains secondary particles formed by agglomeration of multiple primary particles,

The above plurality of primary particles have an average particle size of 1.5 ㎛ or more and 5.0 ㎛ or less as measured from a SEM image, and the particle size of the above primary particles is a particle size based on the major diameter of the primary particles.

The above secondary particles have an average particle diameter (D50) of 7.0 ㎛ or more and 20.0 ㎛ or less based on the volume cumulative distribution measured using a laser diffraction particle size analyzer,

A cathode active material, wherein, with respect to a cross-section of a secondary particle, the size of the cross-section of the secondary particle observed from a SEM image of the cross-section of the secondary particle is within the range of the average particle diameter (D50) of the secondary particle, and the number of cross-sections of primary particles confirmed within a unit area of 5 ㎛ width x 5 ㎛ length within the cross-section of the secondary particle is 1 or more and 100 or less.
In the first paragraph,

A cathode active material, wherein, with respect to a cross-section of a secondary particle, the size of the cross-section of the secondary particle observed from a SEM image of the cross-section of the secondary particle is within the range of the average particle diameter ( D50 ) of the secondary particle, and the number of cross-sections of primary particles confirmed within a unit area of 5 ㎛ width x 5 ㎛ length within the cross-section of the secondary particle is 1 or more and 50 or less.
In the first paragraph,

A cathode active material comprising a lithium transition metal composite oxide containing nickel, cobalt and manganese.
In the first paragraph,

A cathode active material comprising a lithium transition metal composite oxide containing nickel in an amount of 60 mol% or more among the total transition metals.
In the first paragraph,

A cathode active material 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 above chemical formula 1,

M 1 is at least one 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, a+b+c+d=1.
In the first paragraph,

A cathode active material wherein the plurality of primary particles include single crystal primary particles.
In the first paragraph,

The above secondary particles are a cathode active material having an average particle diameter ( D50 ) of 7.0 ㎛ or more and 20.0 ㎛ or less based on a volume cumulative distribution measured using a laser diffraction particle size analyzer.
A positive electrode comprising a positive electrode active material according to any one of claims 1 to 7.
A lithium secondary battery comprising a cathode according to Article 8; a separator interposed between the cathode and the anode; and an electrolyte.