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

Abstract

The present invention relates to a positive electrode active material, and a positive electrode and a lithium secondary battery comprising the same, in which the positive electrode active material can simultaneously solve the conventional problem of secondary particles and the problem of single particles, and the positive electrode active material comprises particles (e.g., particles of the secondary particles) as primary particles, and a lithium secondary battery comprising the positive electrode active material. The present invention provides a lithium secondary battery (e.g., a single particle in the prior art) and a secondary particle formed by aggregating a plurality of primary particles, and thus not only can provide excellent cell characteristics of the lithium secondary battery, such as improved lifespan and reduced gas generation, but also can provide excellent density characteristics to improve energy density.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-00656231, filed with the Korean Intellectual Property Office on April 28, 2023, and Korean Patent Application No. 10-2024-0057118, filed on April 29, 2024, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0004] This invention relates to positive electrode active materials, and positive electrodes and lithium secondary batteries including said positive electrode active materials. Background Technology

[0005] In recent years, with the rapid development of electric vehicle technology, the demand for high-capacity secondary batteries has been increasing. Therefore, people have conducted extensive research on high-nickel (high-Ni) cathode active materials with excellent capacity characteristics.

[0006] For high-Ni cathode active materials formed with a secondary particle structure containing aggregated primary particles, the charging and discharging process of lithium secondary batteries not only causes structural degradation but also has a high probability of causing relatively large changes in the lattice structure constant (i.e., relatively large volume changes per unit lattice). These volume changes can lead to cracks in the cathode active material. Furthermore, even during electrode rolling, pressure can cause cracks to develop in the cathode active material.

[0007] The cracks formed in the high-Ni cathode active material will be further amplified during the charging and discharging process of the lithium secondary battery. Therefore, the cracks, as voids that the electrolyte cannot reach or reduce conductivity, lead to a decrease in the life characteristics of the lithium secondary battery or increase the resistance.

[0008] To minimize the development of cracks with secondary particle structures, efforts are being made to prepare single-particle cathode active materials. However, single-particle cathode active materials have uneven particle size, which increases the particle size distribution of the resulting material after grinding. Furthermore, single-particle cathode active materials have a lower specific surface area, thus exhibiting poorer battery resistance characteristics.

[0009] Therefore, it is necessary to develop a positive electrode active material that can simultaneously solve the typical secondary particle problem and the single particle problem.

[0010] Meanwhile, Korean Patent Publication No. 10-1785262 (Patent Document 1) discloses a large-diameter secondary particle comprising aggregated primary particles, wherein the secondary particles comprise nickel-based lithium transition metal oxides, the primary particles have an average particle size of 3 μm to 5 μm, and the secondary particles have an average particle size of 10 μm to 20 μm. This large-diameter secondary particle, comprising primary particles with an average particle size in the micrometer range, can improve rolling density to minimize cracks caused by rolling, and can enhance specific surface area characteristics through the secondary particle structure to improve battery performance.

[0011] Compared to submicron-sized secondary particles with primary particle diameters less than 1 μm, the preparation of cathode active materials in the form of micron-sized secondary particles, as disclosed in Patent Document 1, may require heat treatment at higher temperatures. However, with increasing heat treatment temperature, the layered structure of lithium transition metal composite oxides degenerates into a rock salt structure, resulting in reduced crystallinity and consequently, a decline in the performance of the cathode active material. In particular, at high heat treatment temperatures, nickel is most likely to cause the degradation of the layered structure of lithium transition metal composite oxides into a rock salt structure; therefore, this degradation is further exacerbated when the amount of nickel in the lithium transition metal composite oxide constituting the cathode active material increases. Therefore, as shown in Patent Document 1, positive electrode active materials with primary particles in the form of secondary particles with a particle size in the micrometer range are generally only suitable for mid-Ni positive electrode active materials with a nickel content of about 50 mol% in the transition metal of lithium transition metal composite oxides. However, for high-Ni positive electrode active materials with excellent capacity characteristics due to the large nickel content in the transition metal of lithium transition metal composite oxides, positive electrode active materials with primary particles in the form of secondary particles with a particle size in the micrometer range cannot be prepared. Summary of the Invention

[0012] Technical issues

[0013] One aspect of the present invention is to provide a high-Ni cathode active material that can simultaneously solve the problems of typical secondary particles and single particles.

[0014] In other words, one aspect of the present invention is to provide a positive electrode active material that, by realizing a positive electrode active material in which the primary particles are in the form of secondary particles with a diameter of micrometers, can improve energy density through excellent density characteristics and can improve cell characteristics, such as improving lifespan and reducing gas generation. This is a high-Ni positive electrode active material with excellent capacity characteristics due to its high nickel content in the transition metal of the lithium transition metal composite oxide.

[0015] Another aspect of the present invention provides a positive electrode and a lithium secondary battery comprising the above-described positive electrode active material.

[0016] Technical solution

[0017] To address the aforementioned problems, the present invention provides a positive electrode active material, comprising a positive electrode of the positive electrode active material and a lithium secondary battery.

[0018] (1) According to one aspect of the present invention, a positive electrode active material is provided, comprising secondary particles aggregated with a plurality of primary particles, wherein the plurality of primary particles have an average particle size of 1.5 μm to 5.0 μm as measured from a scanning electron microscope (SEM) image, the particle size of the primary particles being the particle size relative to the major axis of the primary particle size, the positive electrode active material comprising aluminum (Al), zirconium (Zr), and Mg. 3 lithium transition metal composite oxide, M 3 It is a metallic element with an oxidation number of +4 or higher, and the positive electrode active material includes a coating portion containing cobalt (Co) and boron (B).

[0019] (2) The present invention provides a positive electrode active material as described in (1) above, M 3 It is selected from at least one of titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo) and niobium (Nb).

[0020] (3) The present invention provides a positive electrode active material as described in (1) or (2) above, wherein the positive electrode active material comprises Al in a total weight of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal complex oxide, Zr in a total weight of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal complex oxide, and M in a total weight of 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal complex oxide. 3 .

[0021] (4) The present invention provides a positive electrode active material as described in any one of (1) to (3) above, wherein the positive electrode active material comprises a lithium transition metal composite oxide containing nickel, cobalt and manganese.

[0022] (5) The present invention provides a positive electrode active material as described in any one of (1) to (4) above, wherein the positive electrode active material comprises a lithium transition metal composite oxide in which nickel accounts for more than 60 mol% of the total transition metals.

[0023] (6) The present invention provides a positive electrode active material as described in any one of (1) to (5) above, wherein the positive electrode active material comprises a lithium transition metal composite oxide having an average composition represented by Formula 1 below.

[0024] [Formula 1]

[0025] Li x Nia Co b Mn c M 1 d O2

[0026] In Formula 1, M 1 is selected from at least one of the group consisting of aluminum (Al), zirconium (Zr), boron (B), tungsten (W), molybdenum (Mo), chromium (Cr), niobium (Nb), magnesium (Mg), hafnium (Hf), tantalum (Ta), lanthanum (La), titanium (Ti), strontium (Sr), barium (Ba), cerium (Ce), vanadium (V), fluorine (F), phosphorus (P), sulfur (S), and yttrium (Y), and satisfies 0.9 ≤ x ≤ 1.3, 0.6 ≤ a < 1.0, 0 < b < 0.4, 0 < c < 0.4, 0 ≤ d ≤ 0.2, and a + b + c + d = 1.

[0027] (7) The present invention provides a positive electrode active material as described in any one of (1) to (6) above, wherein the plurality of primary particles include single crystal primary particles.

[0028] (8) The present invention provides a positive electrode active material as described in any one of (1) to (7) above, wherein, according to the volume cumulative distribution measured by a laser diffraction particle size analyzer, the average particle size (D 50 ) of the secondary particles is 7.0 μm to 20.0 μm.

[0029] (9) According to another aspect of the present invention, there is provided a positive electrode including the positive electrode active material as described in any one of (1) to (8) above.

[0030] (10) According to another aspect of the present invention, there is provided a lithium secondary battery including the positive electrode as described in (9) above; a negative electrode; a separator disposed between the positive electrode and the negative electrode, and an electrolyte.

[0031] Advantageous Effects

[0032] The positive electrode active material of the present invention is a high-Ni positive electrode active material, which can simultaneously solve the problems of typical secondary particles and single particles. Among them, the positive electrode active material of the present invention can improve the energy density through excellent density characteristics, as well as improve the life of the lithium secondary battery and reduce the gas generation amount and other cell characteristics by realizing the positive electrode active material in the form of secondary particles with a primary particle size in the micron range. Brief Description of the Drawings

[0033] Figure 1 It is a scanning electron microscope (SEM) image of the cross-section of the positive electrode active material of Example 1;

[0034] Figure 2This is a SEM image of the cross-section of the positive electrode active material in Example 2.

[0035] Figure 3 (A) SEM image of the positive electrode active material of Comparative Example 1, and (B) SEM image of the cross section of the positive electrode active material are shown.

[0036] Figure 4 (A) SEM image of the positive electrode active material of Comparative Example 2, and (B) SEM image of the cross section of the positive electrode active material are shown.

[0037] Figure 5 (A) SEM image of the positive electrode active material of Comparative Example 3, and (B) SEM image of the cross section of the positive electrode active material are shown.

[0038] Figure 6 (A) SEM image of the positive electrode active material of Comparative Example 4, and (B) SEM image of the cross section of the positive electrode active material are shown.

[0039] Figure 7 (A) SEM image of the positive electrode active material of Comparative Example 5, and (B) SEM image of the cross section of the positive electrode active material are shown.

[0040] Figure 8 (A) SEM image of the positive electrode active material of Comparative Example 6, and (B) SEM image of the cross section of the positive electrode active material are shown.

[0041] Figure 9 The segmented image shows multiple lithium composite transition metal oxides, which were segmented based on an artificial intelligence model after image analysis of the SEM image of the positive electrode active material of Example 1.

[0042] Figure 10 The segmented image shows multiple lithium composite transition metal oxides, which were segmented based on image analysis of the SEM image of the positive electrode active material of Example 2 using an artificial intelligence model.

[0043] Figure 11 The segmented image shows multiple lithium composite transition metal oxides, which were segmented based on an artificial intelligence model after image analysis of the SEM image of the positive electrode active material of Comparative Example 1.

[0044] Figure 12 The segmented image shows multiple lithium composite transition metal oxides, which were segmented based on an artificial intelligence model after image analysis of the SEM image of the positive electrode active material of Comparative Example 2.

[0045] Figure 13Electron backscatter diffraction (EBSD) pattern image of the cross section of the positive electrode active material of Comparative Example 4.

[0046] Figure 14 The image shown is an electron probe microanalysis (EPMA) image of the positive electrode active material in Example 1; and

[0047] Figure 15 This is an EPMA image of the positive electrode active material of Example 2. Detailed Implementation

[0048] The invention will be described in more detail below in order to provide a clearer understanding of it.

[0049] It should be understood that the words or terms used in the specification and claims should not be interpreted as having the meaning defined in a common dictionary, and it should also be understood that, based on the principle that the inventor can correctly define the meaning of words or terms to best interpret the invention, these words or terms should be interpreted as having a meaning consistent with their meaning in the context of the relevant field and the technical idea of ​​the invention.

[0050] In this invention, the term "primary particle" refers to the smallest particle unit that can be identified as a whole when the cross-section of the positive electrode active material is observed using a scanning electron microscope (SEM), which can be composed of a single crystal or multiple microcrystals.

[0051] In this invention, the term "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles. The average particle size of the secondary particles can be measured using a particle size analyzer.

[0052] The term "average particle size (D)" in this invention 50 ")" indicates the particle size at the 50% volumetric cumulative distribution based on particle size. After dispersing the target powder in a dispersion medium, the dispersion medium is introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the differences in diffraction patterns caused by particle size as particles pass through the laser beam. The particle size at the 50% volumetric cumulative distribution can then be used to determine the Dsize. 50 .

[0053] In this invention, "major diameter of primary particles" refers to the length of the longest line segment observed in a SEM image of the surface or cross-section of a secondary particle when a line is drawn through two points on the boundary of a primary particle within the primary particle.

[0054] In this invention, the "minor diameter of the primary particle" refers to the length of the shortest line segment when a line is drawn through two points on the boundary of the primary particle, as observed in the SEM image of the surface or cross-section of the secondary particle.

[0055] Positive electrode active material

[0056] This invention provides a positive electrode active material.

[0057] According to an embodiment of the present invention, the positive electrode active material includes secondary particles in which a plurality of primary particles are aggregated, wherein the average particle size of the plurality of primary particles, as measured by SEM images, can be from 1.5 μm to 5.0 μm.

[0058] According to an embodiment of the present invention, a secondary particle is a secondary particle in which a plurality of primary particles are aggregated, wherein it may be a secondary particle in which at least two, or, as a specific example, at least three, primary particles are aggregated.

[0059] According to embodiments of the present invention, the average particle size measured from SEM images of multiple primary particles can be 1.5 μm or more, 1.6 μm or more, 1.7 μm or more, 1.8 μm or more, 1.9 μm or more, 2.0 μm or more, 2.1 μm or more, 2.2 μm or more, 2.3 μm or more, 2.4 μm or more, or 2.5 μm or more, and can also be 5.0 μm or less, 4.9 μm or less, 4.8 μm or less, 4.7 μm or less, 4.6 μm or less, 4.5 μm or less, 4.4 μm or less, 4.3 μm or less, 4.2 μm or less, 4.1 μm or less, 4.0 μm or less, 3.9 μm or less, 3.8 μm or less, 3.7 μm or less, 3.6 μm or less, 3.5 μm or less, 3.4 μm or less, 3.3 μm or less, 3.2 μm or less, 3.1 μm or less, or 3.0 μm or less. Here, when measuring the average particle size of multiple primary particles from SEM images, the particle size of each primary particle can be the particle size relative to the major axis of the primary particle. Within this range, the lifespan of lithium secondary batteries can be further improved, while the rolling density of the cathode active material can also be further improved.

[0060] According to embodiments of the present invention, the positive electrode active material may include a lithium transition metal composite oxide containing nickel, cobalt, and manganese. As a specific example, the positive electrode active material may include a lithium transition metal composite oxide containing at least 60 mol% nickel of all transition metals. The lithium transition metal composite oxide may be primary particles, secondary particles, or the positive electrode active material itself containing them. As a specific example, the positive electrode active material may include secondary particles aggregated with multiple primary particles formed from the lithium transition metal composite oxide.

[0061] According to embodiments of the present invention, the positive electrode active material may include a lithium transition metal composite oxide having an average composition as shown in Formula 1 below.

[0062] [Formula 1]

[0063] Lix Ni a Co b Mn c M 1 d O2

[0064] In Formula 1, M 1 is selected from at least one of the group consisting of aluminum (Al), zirconium (Zr), boron (B), tungsten (W), molybdenum (Mo), chromium (Cr), niobium (Nb), magnesium (Mg), hafnium (Hf), tantalum (Ta), lanthanum (La), titanium (Ti), strontium (Sr), barium (Ba), cerium (Ce), vanadium (V), fluorine (F), phosphorus (P), sulfur (S), and yttrium (Y), and satisfies 0.9 ≤ x ≤ 1.3, 0.6 ≤ a < 1.0, 0 < b < 0.4, 0 < c < 0.4, 0 ≤ d ≤ 0.2, and a + b + c + d = 1.

[0065] According to an embodiment of the present invention, in Formula 1, x is the molar ratio of lithium to transition metal in the lithium transition metal composite oxide, where x can be 0.9 or more, 0.95 or more, or 1.0 or more, and can also be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0066] According to an embodiment of the present invention, in Formula 1, a, b, c, and d can be the molar fractions of nickel (Ni), cobalt (Co), manganese (Mn), and doping element (M1) in the transition metal, respectively. As a specific example, a is the molar fraction of nickel (Ni) in the transition metal, where a can 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 can also be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. In addition, b is the molar fraction of cobalt (Co) in the transition metal, where b can be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and can also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. c is the molar fraction of manganese (Mn) in the transition metal, where c can be greater than 0, 0.01 or more, or 0.05 or more, and can also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. d is the doping element (M 1The mole fraction of d in transition metals, where d can be 0, ≥0.01, ≥0.02, ≥0.03, ≥0.04, ≥0.05, ≥0.06, ≥0.07, ≥0.08, ≥0.09, ≥0.10, ≥0.11, ≥0.12, ≥0.13, ≥0.14, ≥0.15, ≥0.16, ≥0.17, ≥0.18, or 0. The concentration can be above 0.19, or below 0.20, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01. By adjusting the composition of the lithium transition metal composite oxide as described above, the capacity can be further improved.

[0067] According to embodiments of the present invention, a plurality of primary particles may include monocrystalline primary particles, in which case the rolling density of the cathode active material can be further increased. A monocrystalline primary particle refers to a primary particle composed of a single crystal.

[0068] According to an embodiment of the present invention, based on the volume cumulative distribution measured using a laser diffraction particle size analyzer, the average particle size (D) of the secondary particles is... 50The average particle size (D50) of the secondary particles can range from 7.0 μm to 20.0 μm. As a specific example, the average particle size (D50) of the secondary particles can be 7.0 μm or more, 7.1 μm or more, 7.2 μm or more, 7.3 μm or more, 7.4 μm or more, 7.5 μm or more, 7.6 μm or more, 7.7 μm or more, 7.8 μm or more, 7.9 μm or more, 8.0 μm or more, 8.1 μm or more, 8.2 μm or more, 8.3 μm or more, 8.4 μm or more, 8.5 μm or more, 8.6 μm or more, and 8. 7μm and above, 8.8μm and above, 8.9μm and above, or 9.0μm and above; or below 20.0μm, below 19.9μm, below 19.8μm, below 19.7μm, below 19.6μm, below 19.5μm, below 19.4μm, below 19.3μm, below 19.2μm, below 19.1μm, below 19.0μm, below 18.9μm, below 18.8μm, below 18.7μm, below 18.6μm. Below 18.5μm, below 18.4μm, below 18.3μm, below 18.2μm, below 18.1μm, below 18.0μm, below 17.9μm, below 17.8μm, below 17.7μm, below 17.6μm, below 17.5μm, below 17.4μm, below 17.3μm, below 17.2μm, below 17.1μm, below 17.0μm, below 16.9μm, and below 16.8μm. The micrometer diameters are below 16.7 μm, 16.6 μm, 16.5 μm, 16.4 μm, 16.3 μm, 16.2 μm, 16.1 μm, 16.0 μm, 15.9 μm, 15.8 μm, 15.7 μm, 15.6 μm, 15.5 μm, 15.4 μm, 15.3 μm, 15.2 μm, 15.1 μm, or 15.0 μm. Within this range, the rolling density and lifespan of the positive electrode active material can be further increased.

[0069] As a specific example, although the positive electrode active material is a high-Ni positive electrode active material containing lithium transition metal composite oxide with a nickel content of more than 60 mol% in the total transition metal, the multiple primary particles can include primary particles with a particle size of 0.5 μm to 5.0 μm, which are the same as typical single particles. Specifically, they can include micron-sized primary particles larger than 1.0 μm. More specifically, they can include multiple primary particles aggregated together to form an average particle size (D) of 2.0 μm to 3.5 μm as measured by SEM images. 50 It consists of large-diameter secondary particles ranging from 7.0 μm to 20.0 μm, and large particles in the form of secondary particles are formed by the aggregation of primary particles in the form of single particles, which can manifest as large single-particle clusters.

[0070] As described in the background section of this invention, in order to prepare positive electrode active materials in the form of secondary particles with primary particle diameters in the micrometer range, heat treatment at higher temperatures is necessary for secondary particles with primary particle diameters less than 1 μm in the submicrometer range. However, as the heat treatment temperature increases, the layered structure of lithium transition metal composite oxides degenerates into a rock salt structure, leading to reduced crystallinity and consequently, a decline in the performance of the positive electrode active material. In particular, at high heat treatment temperatures, nickel is most likely to cause the layered structure of lithium transition metal composite oxides to degenerate into a rock salt structure; therefore, this degradation is further exacerbated when the amount of nickel in the lithium transition metal composite oxides constituting the positive electrode active material increases. Therefore, generally speaking, positive electrode active materials in the form of secondary particles with a primary particle size in the micrometer range are only suitable for medium-nickel (medium Ni) positive electrode active materials in lithium transition metal composite oxides with a nickel content of about 50 mol% in the transition metal. However, for high-Ni positive electrode active materials with excellent capacity characteristics due to the high nickel content in the transition metal of lithium transition metal composite oxides, it is not possible to prepare positive electrode active materials in the form of secondary particles with a primary particle size in the micrometer range.

[0071] However, since the positive electrode active material of the present invention contains a large amount of nickel in the transition metal of the lithium transition metal composite oxide, even when the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure at high heat treatment temperatures, it can recover from the rock salt structure to the layered structure, thus solving the aforementioned problem. Specifically, the positive electrode active material of the present invention differs from typical medium-nickel positive electrode active materials. Instead, it is a high-Ni positive electrode active material containing lithium transition metal composite oxide with a nickel content of 60 mol% or more in the total transition metal. Because it recovers the layered structure from the rock salt structure formed at high heat treatment temperatures while containing secondary particles with a diameter of micrometers as primary particles, and the lithium transition metal composite oxide has excellent crystallinity, it can simultaneously solve the problems of existing secondary particles and single particles. The positive electrode active material of the present invention can be prepared by restoring the layered structure from the rock salt structure formed by high heat treatment temperature as described above, and the method of restoring the layered structure from the rock salt structure is not limited. However, according to an embodiment of the present invention, the method of restoring the layered structure from the rock salt structure can be to coat a lithium transition metal composite oxide containing the rock salt structure formed by high heat treatment temperature with cobalt (Co).

[0072] According to embodiments of the present invention, multiple primary particles may include disc-shaped primary particles. As a specific example, more than three disc-shaped primary particles may be included. In this case, the cell has excellent lifespan and energy density.

[0073] According to an embodiment of the present invention, in primary particles observed from SEM images of the surface or cross-section of secondary particles, when an imaginary tangent with the most contact points is drawn for each of the two boundary lines of a primary particle existing at an angle of 45° or less relative to its major axis, and an imaginary line intersecting these two tangents is drawn, a disc-shaped primary particle can refer to a particle with an interior angle on the same side ranging from 150° to 210°, a minor axis of 0.3 μm or more, and an aspect ratio (major axis / minor axis) of 1.5 or more. As a specific example, a disc-shaped primary particle can have a minor axis of 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1.0 μm or more. Here, when the minor diameter of the disk-shaped primary particle is 0.3 μm or more and the aspect ratio (major diameter / minor diameter) is 1.5 or more, the area ratio of the (003) plane in the crystal plane of the surface portion of the primary particle can be maximized.

[0074] According to an embodiment of the present invention, in a primary particle observed from a SEM image of the surface or cross-section of a secondary particle, when an imaginary tangent with the most contact points is drawn for each of the boundary lines of two primary particles at an angle of 45° or less relative to the major axis, and an imaginary line intersecting these two tangents is drawn, a disk-shaped primary particle can be defined as one where the interior angle on the same side is in the range of 150° to 210° and the area ratio of the (003) facets in the crystal planes of the surface portion of the primary particle is the largest. Here, when the area ratio of the (003) facets in the crystal planes of the surface portion of the disk-shaped primary particle is the largest, the minor axis of the primary particle can be 0.3 μm or more, and the aspect ratio (major axis / minor axis) can be 1.5 or more. That is, it can be confirmed from the fact that the minor axis of the primary particle is 0.3 μm or more and the aspect ratio (major axis / minor axis) is 1.5 or more that the area ratio of the (003) facets in the crystal planes of the surface portion of the primary particle can be the largest.

[0075] According to an embodiment of the present invention, in a frequency distribution plot showing the cumulative volume distribution measured using a laser diffraction particle size analyzer, where the x-axis value represents the particle size gradually increasing from left to right on a logarithmic scale, and the y-axis value represents the volume distribution gradually increasing from bottom to top, when a triangle is drawn with the peak point at the uppermost point of the y-axis where the peak appears at the mode, and the two contact points of the frequency distribution curve tangent at the full width at half maximum (FWHM) of that mode, the interior angle (θ) of the left contact point of the two contact points of the frequency distribution curve of the positive electrode active material is... L ) and the interior angle (θ R The difference (θ) between L -θ R The angle can be from 6 to 20. As a specific example, the interior angle (θ) at the left contact point... L The interior angle (θ) at the right contact pointR The difference (θ) between L -θ R The value can be 6 or higher, 7 or higher, 8 or higher, 9 or higher, 10 or higher, 11 or higher, 12 or higher, 13 or higher, or 14 or higher; it can also be below 20, below 19, below 18, below 17, below 16, or below 15. The ratio (θ) of the interior angle of the left contact point to the interior angle of the right contact point of the positive electrode active material. L / θ R The value can range from 1.100 to 2.000. As a specific example, the ratio (θ) of the interior angle at the left contact point to the interior angle at the right contact point... L / θ R The values ​​can be 1.100 or higher, 1.110 or higher, 1.120 or higher, 1.130 or higher, 1.140 or higher, 1.150 or higher, 1.160 or higher, 1.170 or higher, 1.180 or higher, 1.190 or higher, 1.200 or higher, 1.210 or higher, 1.220 or higher, 1.230 or higher, 1.240 or higher, 1.250 or higher, 1.260 or higher, 1.270 or higher, 1.280 or higher, 1.290 or higher, 1.300 or higher, 1.310 or higher, 1.320 or higher, 1.330 or higher, 1.340 or higher, or 1.350 or higher. The values ​​can be above 1.360, 1.370, 1.380, 1.390, 1.400, 1.410, 1.420, 1.430, or 1.440, and can also be below 1.450, below 1.460, below 1.470, below 1.480, below 1.490, below 1.500, below 1.550, below 1.600, below 1.650, below 1.700, below 1.750, below 1.800, below 1.850, below 1.900, below 1.950, or below 2.000. Here, the frequency distribution plot can be a single-peaked distribution plot.

[0076] According to an embodiment of the present invention, in a frequency distribution plot showing the cumulative volume distribution measured using a laser diffraction particle size analyzer, where the x-axis value represents the particle size gradually increasing from left to right on a linear scale, and the y-axis value represents the volume distribution gradually increasing from bottom to top, the positive electrode active material can exhibit a positively skewed state. Here, the frequency distribution plot can be a single-peaked distribution plot.

[0077] According to an embodiment of the present invention, the skewness value (S) of the positive electrode active material is compared with the y-value (P) of the peak at the uppermost point of the y-axis of the mode peak that appears according to the volume cumulative distribution. 众数 The ratio of S / P 众数The value can range from 0.037 to 0.150. As a specific example, the skewness value (S) of the peak at the uppermost point of the y-axis of the mode peak of the volumetric cumulative distribution of the positive electrode active material is compared with the y-value (P). 众数 The ratio of S / P 众数 The possible values ​​are 0.037 or higher, 0.038 or higher, 0.039 or higher, 0.040 or higher, 0.041 or higher, 0.042 or higher, 0.043 or higher, 0.044 or higher, 0.045 or higher, 0.046 or higher, 0.047 or higher, 0.048 or higher, 0.049 or higher, 0.050 or higher, 0.051 or higher, 0.052 or higher, 0.053 or higher, and 0. 054 and above, 0.055 and above, 0.056 and above, 0.057 and above, 0.058 and above, 0.059 and above, 0.060 and above, 0.061 and above, 0.062 and above, 0 .063 and above, 0.064 and above, 0.065 and above, 0.066 and above, 0.067 and above, 0.068 and above, 0.069 and above, 0.070 and above, 0.071 and above, 0 .072 and above, 0.073 and above, 0.074 and above, 0.075 and above, 0.076 and above, 0.077 and above, 0.078 and above, 0.079 and above, 0.080 and above, 0.081 and above, 0.082 and above, 0.083 and above, 0.083 and above, 0.084 and above, 0.085 and above, 0.086 and above, 0.087 and above, 0.088 and above, The skewness value (S) can be 0.089 or higher, 0.090 or higher, 0.091 or higher, 0.092 or higher, 0.093 or higher, 0.094 or higher, 0.095 or higher, 0.096 or higher, 0.097 or higher, 0.098 or higher, 0.099 or higher, or 0.100 or higher, and can also be below 0.150, below 0.140, below 0.130, below 0.120, or below 0.110. Here, the skewness value (S) can be calculated according to Equation 3 below.

[0078] [Equation 3]

[0079] Skewness value (S) = 3 × (volume average particle size - (D50)) / standard deviation of positive electrode active material particle size

[0080] According to an embodiment of the present invention, the positive electrode active material can have a surface area of ​​0.20 m², as measured by nitrogen adsorption BET specific surface area analysis. 2 / g to 0.35m 2 The Brunauer-Emmett-Teller (BET) specific surface area is [value missing] g. As a specific example, the BET specific surface area of ​​the positive electrode active material, measured by nitrogen adsorption BET specific surface area analysis, can be 0.20 m² / g. 2 / g or more, 0.21m 2 / g or more, 0.22m 2 / g or more, 0.23m 2 / g or more, 0.24m 2 / g or more, 0.25m 2 / g or more, 0.26m 2 / g or more, 0.27m 2 / g or more, 0.28m 2 / g or more, 0.29m 2 / g or more, 0.30m 2 / g or more, or 0.31m 2 / g or more, and can also be 0.35m 2 / g or less, or 0.34m 2 / g or less. Within this range, DC resistance can be reduced and rolling density improved.

[0081] According to an embodiment of the present invention, based on the volume cumulative distribution of secondary particles measured using a laser diffraction particle size analyzer, the average particle size (D) of the positive electrode active material is... 50 The size ranges from 7.0 μm to 20.0 μm, and the size observed from SEM images of secondary particle cross-sections is within the range of the average particle size (D) of the secondary particles. 50 The number of primary particle cross sections identified within a unit area of ​​5μm width × 5μm length of the secondary particle cross section can range from 1 to 100.

[0082] According to an embodiment of the present invention, for the size observed from the SEM image of the secondary particle cross-section, the average particle size of the secondary particles (D) 50 For the secondary particle cross-section within the range of ), the number of primary particle cross-sections identified within a 5μm wide × 5μm long unit area of ​​the secondary particle cross-section refers to the total number of primary particle cross-sections identified within that unit area. This includes not only primary particles whose entire cross-section is within that unit area, but also primary particles whose cross-section is at least a portion of its cross-section within that unit area. Furthermore, the 5μm wide × 5μm long unit area of ​​the secondary particle cross-section is the unit area at any point on the secondary particle cross-section, and its location is unrestricted as long as it is on the secondary particle cross-section.

[0083] According to an embodiment of the present invention, the size observed in the SEM image of the cross-section of the secondary particles is within the average particle size (D) of the secondary particles. 50Regarding the cross-section of secondary particles within the range of ), the number of primary particles identified within a unit area of ​​5μm width × 5μm length in the cross-section of secondary particles of the positive electrode active material can range from 1 to 100. As specific examples, it can be more than 1, more than 2, more than 3, more than 4, more than 5, more than 6, more than 7, more than 8, more than 9, or more than 10, and it can also be less than 100, less than 95, less than 90, less than 85, less than 80, less than 75, less than 70, less than 65, less than 60, less than 55, less than 50, less than 45, less than 40, less than 35, less than 30, less than 25, less than 20, or less than 15. Under the aforementioned conditions, the positive electrode active material can exhibit multiple primary particles including primary particles with a particle size of 0.5 μm to 5.0 μm, the same as typical single particles. Specifically, it includes micron-sized primary particles larger than 1.0 μm, and more specifically, it includes aggregates of multiple primary particles with an average particle size (D) of 2.0 μm to 3.5 μm as measured from SEM images. 50 These are large-diameter secondary particles ranging from 7.0 μm to 20.0 μm.

[0084] According to an embodiment of the present invention, based on the volume cumulative distribution of secondary particles measured using a laser diffraction particle size analyzer, the average particle size (D) of the positive electrode active material is... 50 The size ranged from 7.0 μm to 20.0 μm, and the size observed in the electron backscatter diffraction (EBSD) pattern of the SEM image of the secondary particle cross-section (measured under the following conditions: accelerating voltage 20 kV, WD 16 mm, measurement magnification 5,000x (16 μm width × 16 μm height), step size 0.025 μm) was within the average particle size (D) of the secondary particles. 50 For secondary particle cross sections within the range of ), the number of grain cross sections identified within a unit area of ​​5μm width × 5μm length of the secondary particle cross section can range from 1 to 150.

[0085] According to an embodiment of the present invention, the size observed in the electron backscatter diffraction (EBSD) pattern of the SEM image of the secondary particle cross-section (measured under the following conditions: accelerating voltage: 20 kV, WD: 16 mm, measurement magnification: 5,000x (16 μm width × 16 μm height), step size: 0.025 μm) is in the average particle size (D) of the secondary particles. 50For the cross-section of secondary particles within the range of ), the number of grain cross-sections identified within a unit area of ​​5μm width × 5μm length of the secondary particle cross-section refers to the number of cross-sections of all grains identified within that unit area. This includes not only grains whose entire cross-section is contained within that unit area, but also grains whose cross-section is at least partially contained within that unit area. Furthermore, the 5μm width × 5μm length unit area within the cross-section of the secondary particle is the unit area at any point on the cross-section of the secondary particle, where the location is unrestricted as long as the unit area is on the cross-section of the secondary particle.

[0086] According to an embodiment of the present invention, the size observed in the electron backscatter diffraction (EBSD) pattern of the SEM image of the secondary particle cross-section (measured under the following conditions: accelerating voltage: 20 kV, WD: 16 mm, measurement magnification: 5,000x (16 μm width × 16 μm height), step size: 0.025 μm) is in the average particle size (D) of the secondary particles. 50 Regarding the cross-section of secondary particles within the range of ), the number of grains identified within a unit area of ​​5μm width × 5μm length in the cross-section of secondary particles of the positive electrode active material can be in the range of 1 to 150. As specific examples, it can be more than 1, more than 2, more than 3, more than 4, more than 5, more than 6, more than 7, more than 8, more than 9, and it can also be less than 150, less than 145, less than 140, less than 135, less than 130, less than 125, less than 120, less than 115, less than 110, less than 105, less than 100, less than 95, less than 90, less than 85, less than 80, less than 75, less than 70, less than 65, less than 60, less than 55, less than 50, less than 45, less than 40, less than 35, less than 30, less than 25, or less than 20. Under the aforementioned conditions, the positive electrode active material can exhibit multiple primary particles including primary particles with a particle size of 0.5 μm to 5.0 μm, the same as typical single particles. Specifically, it includes micron-sized primary particles larger than 1.0 μm, and more specifically, it includes aggregates of multiple primary particles with an average particle size (D) of 2.0 μm to 3.5 μm as measured from SEM images. 50 These are large-diameter secondary particles ranging from 7.0 μm to 20.0 μm.

[0087] According to an embodiment of the present invention, the single crystal formation degree of the positive electrode active material can reach 0.15 μm. 3 The degree of single-crystal formation is calculated using the following Equation 1.

[0088] [Equation 1]

[0089]

[0090] In Equation 1, the size observed in the electron backscatter diffraction (EBSD) pattern of the SEM image of the secondary particle cross-section (measured under the following conditions: accelerating voltage: 20 kV, WD: 16 mm, measurement magnification: 5000x (16 μm width × 16 μm height), step size: 0.025 μm) is the average particle size of the secondary particles (D). 50 For the cross-section of secondary particles within the range of ) , among all the identifiable grains in the cross-section, for a cross-sectional area of ​​0.196 μm 2 The above grain cross-sections, the radius (grain) is the radius of the grain cross-section assuming the grain cross-section is circular, and n is the number of grains.

[0091] According to an embodiment of the present invention, the single-crystal formation degree of the positive electrode active material can reach 0.15 μm. 3 Up to 12.70μm 3 The degree of single-crystal formation is calculated using Equation 1. As a specific example, the degree of single-crystal formation of the positive electrode active material calculated using Equation 1 can be 0.15 μm. 3 Above, 0.20μm 3 Above, 0.25μm 3 Above, 0.30μm 3 Above, 0.35μm 3 Above, 0.40μm 3 Above, 0.45μm 3 Above, 0.50μm 3 Above, 0.55μm 3 Above, 0.60μm 3 Above, 0.65μm 3 Above, 0.70μm 3 Above, 0.75μm 3 Above, 0.80μm 3 Above, 0.85μm 3 Above, 0.90μm 3 Above, 0.95μm 3 Above, 1.00μm 3 Above, or 1.05μm 3 The above, and its upper limit is not particularly limited, can also be 20.00μm. 3 Below, 19.00μm 3 Below, 18.00μm 3 Below, 17.00μm 3 Below, below 16.00μm3, below 15.00μm3, below 14.00μm3, below 13.00μm3, or below 12.70μm 3the following.

[0092] According to embodiments of the present invention, the positive electrode active material may include a lithium transition metal composite oxide containing aluminum (Al), yttrium (Y), and zirconium (Zr). As a specific example, the positive electrode active material may include aluminum (Al), yttrium (Y), and zirconium (Zr) as doping elements.

[0093] According to embodiments of the present invention, the total weight of the lithium transition metal complex oxide may contain 500 ppm to 3,000 ppm of aluminum (Al). As a specific example, the aluminum (Al) content relative to the total weight of the lithium transition metal complex oxide may be 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more, and may also be 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0094] According to embodiments of the present invention, yttrium (Y) may be present in amounts ranging from 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal complex oxide. As a specific example, the yttrium (Y) content relative to the total weight of the lithium transition metal complex oxide may be 100 ppm or more, 200 ppm or more, 300 ppm or more, 400 ppm or more, or 500 ppm or more, and may also be less than 2,000 ppm, less than 1,900 ppm, less than 1,800 ppm, less than 1,700 ppm, less than 1,600 ppm, or less than 1,500 ppm.

[0095] According to embodiments of the present invention, the zirconium (Zr) content may be between 500 ppm and 5,000 ppm relative to the total weight of the lithium transition metal complex oxide. As a specific example, the zirconium (Zr) content relative to the total weight of the lithium transition metal complex oxide may be 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more, and may also be 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.

[0096] According to embodiments of the present invention, the positive electrode active material may include a lithium transition metal composite oxide having an average composition as shown in Formula 2 below.

[0097] [Equation 2]

[0098] Li x [Ni a Co b Mn c Al e Y f Zr g M2 d O 2-y A y

[0099] In Formula 2, M 2 is at least one of B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, and S, A is at least one of F, chlorine (Cl), bromine (Br), iodine (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, and 0 ≤ y ≤ 0.2.

[0100] According to an embodiment of the present invention, in Formula 2, x is the molar ratio of lithium to transition metal in the lithium transition metal composite oxide, where x can be 0.9 or more, 0.95 or more, or 1.0 or more, and can also be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0101] According to an embodiment of the present invention, in Formula 2, a, b, c, d, e, f, and g can be the mole fractions of nickel (Ni), cobalt (Co), manganese (Mn), doping element (M 2 ), aluminum (Al), yttrium (Y), and zirconium (Zr) in the transition metal, respectively. As a specific example, a is the mole fraction of nickel (Ni) in the transition metal, where a can 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 can also be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. In addition, b is the mole fraction of cobalt (Co) in the transition metal, where b can be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and can also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. c is the mole fraction of manganese (Mn) in the transition metal, where c can be greater than 0, 0.01 or more, or 0.05 or more, and can also be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. d is the doping element (M 2The mole fraction of d in transition metals, where d can be 0, ≥0.01, ≥0.02, ≥0.03, ≥0.04, ≥0.05, ≥0.06, ≥0.07, ≥0.08, ≥0.09, ≥0.10, ≥0.11, ≥0.12, ≥0.13, ≥0.14, ≥0.15, ≥0.16, ≥0.17, ≥0.18, or 0. The mole fraction of aluminum (Al) in the transition metal can be greater than 0.19, or less than 0.20, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01. e represents the mole fraction of aluminum (Al) in the transition metal, where e can be greater than 0, greater than 0.001, greater than 0.002, greater than 0.003, greater than 0.004, or greater than 0.005, or less than 0.01, less than 0.009, or less than 0.008. f represents the mole fraction of yttrium (Y) in the transition metal, where f can be greater than 0, greater than 0.0001, greater than 0.0002, or greater than 0.0003, or less than 0.0006, less than 0.0005, or less than 0.0004. g represents the mole fraction of zirconium (Zr) in the transition metal, where g can be greater than 0, greater than 0.0001, or greater than 0.0002, or less than 0.0005, or less than 0.0004.

[0102] According to an embodiment of the present invention, in Formula 2, y is the molar ratio of oxygen-substituted A element in the lithium transition metal composite oxide, wherein y can be 0, greater than 0, greater than 0.01, greater than 0.02, or greater than 0.03, or less than 0.2, less than 0.15, or less than 0.1.

[0103] According to embodiments of the present invention, the positive electrode active material may include aluminum (Al), zirconium (Zr), and M. 3 Transition metal composite oxides. As specific examples, positive electrode active materials may include aluminum (Al), zirconium (Zr), and Mn. 3 As a dopant element.

[0104] According to an embodiment of the present invention, M 3 It can be a metallic element with an oxidation state of +4 or higher. As a specific example, M... 3 It can be at least one selected from titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo), and niobium (Nb).

[0105] According to embodiments of the present invention, the total weight of the lithium transition metal complex oxide may contain 500 ppm to 3,000 ppm of aluminum (Al). As a specific example, the aluminum (Al) content relative to the total weight of the lithium transition metal complex oxide may be 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more, and may also be 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0106] According to embodiments of the present invention, the total weight of the lithium transition metal complex oxide may contain 500 ppm to 3,000 ppm of zirconium (Zr). As a specific example, the zirconium (Zr) content may be 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or more, and may also be 3,000 ppm or less, 2,500 ppm or less, or 2,000 ppm or less.

[0107] According to embodiments of the present invention, M may be present in amounts ranging from 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal composite oxide. 3 As a specific example, relative to the total weight of lithium transition metal composite oxides, M 3 The content can be above 100ppm, above 200ppm, above 300ppm, above 400ppm, or above 500ppm, and the content can also be below 2,000ppm, below 1,900ppm, below 1,800ppm, below 1,700ppm, below 1,600ppm, or below 1,500ppm.

[0108] According to an embodiment of the present invention, the positive electrode active material includes a coating portion formed on at least one of the surface of primary particles, the interface of primary particles, and the surface of secondary particles, wherein the coating portion may include at least one coating element selected from the group consisting of cobalt (Co) and boron (B).

[0109] As a specific example, the positive electrode active material may include secondary particles in which multiple primary particles are aggregated, and in this case, the multiple primary particles may have an average particle size of 1.5 μm to 5.0 μm as measured from SEM images. The positive electrode active material may include aluminum (Al), zirconium (Zr), and argonium (M). 3 A lithium transition metal composite oxide (which is a metal element with an oxidation state of +4 or higher) and includes a coating portion containing cobalt (Co) and boron (B).

[0110] According to an embodiment of the present invention, the coating portion may be an island-shaped coating portion formed on at least one of the surface of the primary particle, the interface of the primary particle, and the surface of the secondary particle.

[0111] According to an embodiment of the present invention, the coating portion may be a coating layer formed around at least one of the surfaces of primary particles, the interfaces of primary particles, and the surfaces of secondary particles.

[0112] According to embodiments of the present invention, the coating portion may include at least one of the following: a coating portion containing cobalt (Co), a coating portion containing cobalt (Co) and boron (B), and a coating portion containing boron (B).

[0113] According to embodiments of the present invention, the coating portion may include a coating portion wherein a cobalt (Co)-containing coating portion, a cobalt (Co) and boron (B)-containing coating portion, and a boron (B)-containing coating portion are sequentially formed.

[0114] According to an embodiment of the present invention, the coated portion may include cobalt boron oxide.

[0115] According to an embodiment of the present invention, when a positive electrode active material is placed in a cylindrical mold with a diameter of 13 mm and an automatic pelletizer is used to apply force until the force reaches 9,000 kgf to form granules, the positive electrode active material can have a particle size of 3.60 g / cm³, calculated by the following equation 2. 3 The above rolling density.

[0116] [Equation 2]

[0117] Rolled density (g / cm³) 3 = Weight of positive electrode active material (g) / Volume of particles (c) m3 )

[0118] According to an embodiment of the present invention, the positive electrode active material may have a concentration of 3.60 g / cm³, calculated by Equation 2. 3 The rolling density mentioned above, as a specific example, can be 3.61 g / cm³. 3 Above, 3.62 g / cm 3 Above, 3.63 g / cm 3 Above, 3.64 g / cm 3 Above, 3.65g / cm 3 Above, 3.66 g / cm 3 Above, 3.67 g / cm 3 Above, 3.68g / cm 3 Above, 3.69 g / cm 3 Above, 3.70 g / cm 3Above, or 3.71 g / cm 3 The above has no specific upper limit, but it can be 10.0 g / cm³. 3 the following.

[0119] According to an embodiment of the present invention, for a lithium secondary battery comprising a positive electrode containing a positive electrode active material, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte, when the lithium secondary battery is charged with a current of 0.5C and then discharged with a current of 1.0C, the discharge capacity of the positive electrode active material can be more than 92.0% of the discharge capacity when charged with a current of 0.5C and then discharged with a current of 0.1C. Here, the discharge capacity of the lithium secondary battery is tested based on the output characteristics of the positive electrode active material, and there are no particular restrictions on components other than the positive electrode active material as long as they can be used in the lithium secondary battery. As a specific example, the discharge capacity of the positive electrode active material when charging the lithium secondary battery with a current of 0.5C and then discharging it with a current of 1.0C can be more than 92.0%, 92.1%, 92.2%, 92.3%, 92.4%, 92.5%, 92.6%, 92.7%, 92.8%, 92.9%, 93.0%, or 93.1% of the discharge capacity when charging the lithium secondary battery with a current of 0.5C and then discharging it with a current of 0.1C. There is no particular upper limit, but it can be less than 100%.

[0120] According to an embodiment of the present invention, for a lithium secondary battery comprising a positive electrode containing a positive electrode active material, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte, when the lithium secondary battery is charged at a current of 0.5C and then discharged at a current of 2.0C, the discharge capacity of the positive electrode active material can be more than 89.0% of the discharge capacity when charged at a current of 0.5C and then discharged at a current of 0.1C. Here, the discharge capacity of the lithium secondary battery is tested based on the output characteristics of the positive electrode active material, and there are no particular restrictions on components other than the positive electrode active material as long as they can be used in the lithium secondary battery. As a specific example, the discharge capacity of the positive electrode active material when charging a lithium secondary battery with a current of 0.5C and then discharging it with a current of 2.0C can be more than 89.0%, 89.1%, 89.2%, 89.3%, 89.4%, 89.5%, 89.6%, 89.7%, 89.8%, 89.9%, 90.0%, 90.1%, 90.2%, 90.3%, or 90.4% of the discharge capacity when charging a lithium secondary battery with a current of 0.5C and then discharging it with a current of 0.1C. There is no particular upper limit, but it can be less than 100%.

[0121] According to an embodiment of the present invention, when the volume value of each primary particle observed from a SEM image (measurement magnification of 3,000x) of the secondary particle surface is calculated according to Equation 5 below, the positive electrode active material can have a single particle formation degree (Dv) corresponding to the volume diameter at 50% of the cumulative volume distribution of primary particles ranging from 1.2 μm to 3.8 μm. 50 ).

[0122] [Equation 5]

[0123] Volume = (4π / 3) × radius 3

[0124] In equation 5,

[0125] The radius is the radius of the surface of the primary particle when the surface of the primary particle is assumed to be circular as observed from the SEM image (measured at 3,000x magnification) of the secondary particle surface.

[0126] As a specific example, the single-particle formation degree (Dv) of positive electrode active materials 50 The micrometer can be 1.2μm or larger, 1.3μm or larger, 1.4μm or larger, 1.5μm or larger, 1.6μm or larger, or 1.65μm or larger, or it can be less than 3.8μm, less than 3.7μm, less than 3.6μm, less than 3.59μm, less than 3.58μm, less than 3.57μm, less than 3.56μm, or less than 3.55μm.

[0127] Preparation method of positive electrode active material

[0128] This invention provides a method for preparing a positive electrode active material.

[0129] According to an embodiment of the present invention, the method for preparing the positive electrode active material can be the above-described method for preparing the positive electrode active material.

[0130] According to an embodiment of the present invention, the method for preparing a positive electrode active material can be carried out by including a step (S10) of mixing a positive electrode active material precursor containing nickel, cobalt and manganese with a lithium raw material and sintering the mixture to prepare a sintered product.

[0131] According to an embodiment of the present invention, step (S10) can be performed by the following methods: a method of sintering in one sintering step by temperature segment (one-step method), a method of performing two sintering steps separately (two-step method), and a method of pre-sintering before sintering in one sintering step by temperature segment (pre-sintering method).

[0132] According to an embodiment of the present invention, the one-step method is a method of continuously sintering in two temperature segments in one sintering step, wherein the mixture of the cathode active material precursor and the lithium raw material is sintered in the first stage, and then the second stage sintering can be immediately performed by changing the temperature segment. At this time, the second stage sintering can be performed at a lower temperature than the first stage sintering, and each sintering temperature can be adjusted according to the amount of nickel. By adjusting the temperature, the shape and size of the primary particles and the average particle size of the secondary particles can be adjusted.

[0133] According to an embodiment of the present invention, the two-step method is a method of performing primary sintering and secondary sintering separately, wherein the method may be to perform primary sintering on the mixture of the cathode active material precursor and the lithium raw material, and after grinding the first sintered product prepared by the primary sintering, perform secondary sintering on the grinding product. In this case, the secondary sintering can be performed at a lower temperature than the primary sintering, and each sintering temperature can be adjusted according to the amount of nickel. By adjusting the temperature, the shape, size of the primary particles and the average particle size of the secondary particles can be adjusted.

[0134] According to an embodiment of the present invention, the pre-sintering method is a method of performing pre-sintering before one-step sintering, wherein the mixture of the cathode active material precursor and the lithium raw material is pre-sintered, and the pre-sintered product can be subjected to the one-step method. In this case, the pre-sintering can be performed at a lower temperature than the one-step sintering, and each sintering temperature can be adjusted according to the amount of nickel. By adjusting the temperature, the shape and size of the primary particles and the average particle size of the secondary particles can be adjusted.

[0135] According to an embodiment of the present invention, the cathode active material precursor may contain nickel accounting for more than 60 mol% in the transition metal. As a specific example, the cathode active material precursor may be a transition metal hydroxide containing nickel, cobalt and manganese, and the content of nickel in the transition metal is more than 60 mol%. As a specific example, the transition metal hydroxide may have an average composition represented by the following formula 3.

[0136] [Formula 3]

[0137] Ni a' Co b' Mn c'( OH)2

[0138] In formula 3, 0.6 ≤ a' < 1.0, 0 < b' < 0.4, 0 < c' < 0.4 and a' + b' + c' = 1 are satisfied.

[0139] According to an embodiment of the present invention, in Formula 3, a', b', and c' can be the mole fractions of nickel (Ni), cobalt (Co), and manganese (Mn) in the transition metal, respectively. As a specific example, a' is the mole fraction of nickel (Ni) in the transition metal, wherein a' can 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 can also be less than 1.0, less than 0.99, less than 0.98, less than 0.97, or less than 0.96. Furthermore, b' represents the mole fraction of cobalt (Co) in the transition metal, where b' can be greater than 0, greater than 0.01, greater than 0.02, or greater than 0.03, or less than 0.4, less than 0.3, less than 0.2, less than 0.1, less than 0.09, less than 0.08, less than 0.07, less than 0.06, or less than 0.05. c' represents the mole fraction of manganese (Mn) in the transition metal, where c' can be greater than 0, greater than 0.01, or greater than 0.05, or less than 0.4, less than 0.3, less than 0.2, less than 0.1, less than 0.09, less than 0.08, less than 0.07, less than 0.06, or less than 0.05.

[0140] According to embodiments of the present invention, lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, hydroxides, or hydroxy oxides can be used as lithium raw materials, such as Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or mixtures thereof.

[0141] According to an embodiment of the present invention, step (S10) can also be performed using at least one doping material 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 material can be an acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or hydroxyoxide containing the above elements. As a specific example, the doping material can be Al2O3, Al(OH)3, Al(NO3)3·9H2O, Al2(SO4)3, Y2O3, or ZrO2.

[0142] According to embodiments of the present invention, the doping material may include Al, Y, and Zr. Additionally, the doping material may include Al, Zr, and a metal element with an oxidation state of +4 or higher (M). 3 ).

[0143] According to an embodiment of the present invention, when mixing the positive electrode active material precursor and the lithium raw material in step (S10), the molar ratio (Li / M) of lithium (Li) in the lithium raw material to the transition metal (M) in the positive electrode active material precursor can be from 0.9 to 1.3. As a specific example, Li / M can be 0.9 or more, 0.95 or more, or 1.0 or more, or 1.1 or less, 1.07 or less, 1.05 or less, or 1.04 or less, and the Li / M can be adjusted according to the amount of nickel in the transition metal.

[0144] According to an embodiment of the present invention, the method for preparing the positive electrode active material may further include a step (S20) of coating the positive electrode active material prepared in step (S10). As a specific example, step (S20) may be performed by comprising at least one coating material selected from the group consisting of Co and B. Furthermore, step (S20) may be performed by further comprising an Al coating material.

[0145] According to an embodiment of the present invention, the coating in step (S20) can be performed by simultaneously coating each coating material or by sequentially coating each coating material. As a specific example, the coating in step (S20) may include: a step (S21) of mixing the positive electrode active material with Co coating material and Al coating material and performing heat treatment; and a step (S22) of mixing the coating product prepared in step (S21) with B coating material and performing heat treatment.

[0146] According to embodiments of the present invention, the Co coating material can be a cobalt hydroxide, such as Co(OH)2; the Al coating material can be an aluminum hydroxide, such as Al(OH)3; and the B coating material can be H3BO3.

[0147] According to an embodiment of the present invention, when performing steps (S10) and (S20), the method for preparing the positive electrode active material may include a step of grinding the sintered product as needed after sintering, wherein the grinding may be performed by a grinding device, as long as it is capable of grinding the positive electrode active material, without any particular limitation.

[0148] According to embodiments of the present invention, doping raw materials and coating raw materials can be added and adjusted to meet the doping element content and coating element content of the above-mentioned positive electrode active material.

[0149] positive electrode

[0150] This invention provides a positive electrode comprising a positive electrode active material.

[0151] According to an 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 above-described positive electrode active material.

[0152] According to embodiments of the present invention, the positive electrode current collector may include a highly conductive metal, and there are no particular limitations, as long as it is not reactive within the voltage range of the battery and the positive electrode active material layer can easily adhere to it. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., can be used as the positive electrode current collector. Furthermore, the positive electrode current collector can typically have a thickness of 3 μm to 500 μm, and minute irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various shapes, such as films, sheets, foils, meshes, porous bodies, foams, nonwoven fabrics, etc.

[0153] According to embodiments of the present invention, in addition to the positive electrode active material, the positive electrode active material layer may optionally include a binder and a conductive agent as needed. In this case, the content of the positive electrode active material relative to the total weight of the positive electrode active material layer can be from 80% to 99% by weight, for example, from 85% to 98.5% by weight, and excellent capacity characteristics can be obtained within this range.

[0154] According to embodiments of the present invention, the conductive agent is used to provide conductivity to the electrode, wherein any conductive agent can be used without particular limitation, as long as it has suitable electronic conductivity and does not cause adverse chemical changes in the battery. Specific examples of the conductive agent may be graphite, such as natural or artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking carbon black, and carbon fibers; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive tubes, such as carbon nanotubes; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one or a mixture of two or more thereof may be used. The content of the conductive agent relative to the total weight of the positive electrode active material layer may be from 0.1% by weight to 15% by weight.

[0155] According to embodiments of the present invention, the adhesive improves the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples of the adhesive may be polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid and polymers thereof in which hydrogen is replaced by lithium (Li), sodium (Na) or calcium (Ca), or various copolymers thereof, and any one or a mixture of two or more thereof may be used. The content of the adhesive relative to the total weight of the positive electrode active material layer may be from 0.1% by weight to 15% by weight.

[0156] According to embodiments of the present invention, a positive electrode can be prepared using a typical method for preparing a positive electrode, the difference being the use of the aforementioned positive electrode active material. Specifically, a composition for forming a positive electrode active material layer, prepared by dissolving or dispersing the positive electrode active material, along with optional binders and conductive agents, in a solvent, is coated onto a positive electrode current collector. The positive electrode can then be prepared by drying and calendering the coated positive electrode current collector, or by casting the composition for forming the positive electrode active material layer onto a separate support, and then pressing the film layer separated from the support onto the positive electrode current collector.

[0157] According to embodiments of the present invention, the solvent can be a solvent commonly used in the art, including dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and any one or a mixture of two or more thereof can be used. Considering the coating thickness and manufacturing yield of the slurry, if the solvent can dissolve or disperse the positive electrode active material, conductive agent, binder, and dispersant, the amount of solvent used is sufficient, and a viscosity that provides excellent thickness uniformity during the subsequent positive electrode preparation coating process can be allowed.

[0158] Lithium secondary batteries

[0159] The present invention provides a lithium secondary battery including the positive electrode.

[0160] According to embodiments of the present invention, the lithium secondary battery may include a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte. Furthermore, the lithium secondary battery may optionally include: a battery container for housing an electrode assembly composed of the positive electrode, negative electrode, and separator; and a seal for sealing the battery container.

[0161] According to an embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0162] According to embodiments of the present invention, the negative electrode current collector is not particularly limited, as long as it has high conductivity and does not cause adverse chemical changes in the battery. For example, it can be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Furthermore, the negative electrode current collector can typically have a thickness of 3 μm to 500 μm, and similar to the positive electrode current collector, microscopic irregularities can be formed on the surface of the current collector to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes, such as films, sheets, foils, meshes, porous bodies, foams, nonwoven fabrics, etc.

[0163] According to embodiments of the present invention, in addition to the negative electrode active material, the negative electrode active material layer may optionally include an adhesive and a conductive agent as needed.

[0164] According to embodiments of the present invention, compounds capable of reversibly inserting and de-intercalating lithium can be used as negative electrode active materials. Specific examples of negative electrode active materials can be carbonaceous materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metal compounds that can be alloyed with lithium, such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), Si alloys, Sn alloys, or Al alloys; and metal oxides that can be doped or undoped with lithium, such as SiO₂. β (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof, can be used. Furthermore, thin films of metallic lithium can be used as anode active materials. Additionally, both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Typical examples of low-crystallinity carbon can be soft carbon and hard carbon, while typical examples of high-crystallinity carbon can be irregular, planar, sheet-like, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature sintered carbon, such as coke derived from petroleum or coal tar pitch. The content of the anode active material can be from 80% to 99% by weight relative to the total weight of the anode active material layer.

[0165] According to embodiments of the present invention, the adhesive of the negative electrode active material layer is a component that facilitates adhesion between the conductive agent, the active material, and the current collector, and the amount of adhesive added is typically from 0.1% to 10% by weight relative to the total weight of the negative electrode active material layer. Examples of adhesives may be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0166] According to embodiments of the present invention, the conductive agent in the negative electrode active material layer is a component used to further improve the conductivity of the negative electrode active material, and the amount of conductive agent added relative to the total weight of the negative electrode active material layer can be 10% by weight or less, preferably 5% by weight or less. There are no particular limitations on the conductive agent, as long as it is conductive and does not cause adverse chemical changes in the battery. For example, conductive agents such as: graphite such as natural or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fiber or metal fiber; fluorocarbons; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or polyphenylene derivatives.

[0167] According to an embodiment of the present invention, the negative electrode can be prepared by coating a composition forming a negative electrode active material layer onto a negative electrode current collector and drying the coated negative electrode current collector. The composition forming the negative electrode active material layer is prepared by dissolving or dispersing negative electrode active material particles, along with optional binders and conductive agents, in a solvent. Alternatively, it can be prepared by casting the composition forming the negative electrode active material layer onto a separate support and then pressing the film layer separated from the support onto the negative electrode current collector.

[0168] According to embodiments of the present invention, the separator separates the negative and positive electrodes and provides a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is generally used in lithium secondary batteries. Specifically, a separator with high moisture retention capacity for the electrolyte and low resistance to the transfer of electrolyte ions can be used. Specifically, porous polymer membranes can be used, such as porous polymer membranes prepared from polyolefin polymers, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures having two or more of these layers. Furthermore, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers. In addition, coated separators comprising ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and separators with single-layer or multi-layer structures can optionally be used.

[0169] According to embodiments of the present invention, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used to prepare lithium secondary batteries, but the present invention is not limited thereto. As a specific example, the electrolyte may contain an organic solvent and a lithium salt.

[0170] According to embodiments of the present invention, any organic solvent can be used without particular limitation, as long as it can serve as a medium for the movement of ions involved in the electrochemical reaction of the battery. Specifically, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as butyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic C2-C20 hydrocarbon group, and may include double-bonded aromatic rings or ether bonds); amides such as dimethylformamide; dioxolane solvents such as 1,3-dioxolane; or sulfolane can be used as organic solvents. Among these solvents, carbonate solvents are preferred, and more preferably, a mixture of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant and low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) that can improve the charge and discharge performance of the battery is preferred.

[0171] According to embodiments of the present invention, lithium salts can be used without particular limitation, as long as they are compounds capable of providing lithium ions for use in lithium secondary batteries. Specifically, the anion of the lithium salt can be at least one selected from the group consisting of: F -Cl - ,Br - I - NO3 - N(CN)2 - BF4 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - Furthermore, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2 can be used as lithium salts. The concentration range of the lithium salt can be from 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, excellent electrolyte performance can be obtained due to the appropriate conductivity and viscosity of the electrolyte, and lithium ions can move efficiently.

[0172] According to embodiments of the present invention, in order to improve battery life characteristics, suppress battery capacity reduction, and increase battery discharge capacity, in addition to the above-mentioned electrolyte components, the electrolyte may further contain at least one additive, such as alkylene carbonate halocarbonates, such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, hexaphosphotriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidinanes, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the content of these additives relative to the total weight of the electrolyte may be from 0.1% by weight to 5% by weight.

[0173] Because lithium secondary batteries containing the positive electrode active material of this invention stably exhibit excellent capacity properties, output characteristics, and lifespan characteristics, they are suitable for portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0174] The shape of the lithium secondary battery of the present invention is not particularly limited, and it can be cylindrical, prismatic, pouch-shaped, or coin-shaped.

[0175] The lithium secondary battery according to the present invention can be used not only as a battery cell for use as a power source for small devices, but also as a unit cell in medium and large battery modules comprising multiple battery cells.

[0176] Therefore, according to another embodiment of the present invention, a battery module including a lithium secondary battery as a unit cell and a battery pack including the battery module are provided.

[0177] According to an embodiment of the present invention, the battery module or battery pack can be used as a power source for at least one of the following: large and medium-sized power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEVs); or energy storage systems.

[0178] In the following, embodiments of the present disclosure will be described in detail in a manner readily practiced by those skilled in the art. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0179] Examples and Comparative Examples

[0180] Example 1

[0181] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.89 Co 0.03 Mn 0.08 (OH)2 transition metal complex hydroxide (D 50 Li(OH)3 (10.2 μm) was mixed with LiOH to make the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) 1.04. Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, TiO2, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and they were mixed to prepare a mixture.

[0182] The mixture was sintered at 850°C for 6 hours in an oxygen atmosphere, followed by sintering at 800°C for 9 hours to obtain the sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxides with an average particle size (D). 50 The thickness is 9.8 μm, and the composition is LiNi. 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Ti 0.0010 Zr0.0015 O2, and in the form of secondary particles aggregated from primary particles.

[0183] Co(OH)₂ was added to the lithium transition metal oxide in the secondary particulate form prepared above, such that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and 500 ppm of Al(OH)₃ was added relative to the total weight of the lithium transition metal oxide in the secondary particulate form prepared above, and the mixture was uniformly mixed to prepare a mixture. The mixture was sintered at 740°C for 3 hours in an oxygen atmosphere, and then sintered at 500°C for 3 hours to obtain a first coated product. The first coated product was ground at room temperature to achieve an average particle size (D). 50 A positive electrode active material with a particle size of 10.2 μm was prepared, wherein a coating containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the positive electrode active material including the coating is LiNi. 0.8641 Co 0.049 1Mn 0.0777 Al 0.0066 Ti 0.0010 Zr 0.0015 O2.

[0184] H3BO3 was added at a rate of 500 ppm relative to the total weight of the first coated product after grinding and mixed to prepare a mixture. The mixture was heat-treated in air at 330°C for 5 hours to obtain a second coated product. The second coated product was ground at room temperature to achieve an average particle size (D... 50 A cathode active material with a particle size of 10.2 μm is prepared, wherein a coating containing Co, Al, and B is formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material including the coating is LiNi. 0.8602 Co 0.048 9Mn 0.0773 Al 0.0066 Ti 0.0010 Zr 0.0015 B 0.0045 O2.

[0185] Example 2

[0186] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.89 Co 0.03 Mn 0.08 (OH)2 transition metal complex hydroxide (D 50Lithium (Li) was mixed with LiOH at a molar ratio of 10.2 μm to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) to achieve a molar ratio of 1.04. Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, Nb2O5, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and then mixed to prepare the mixture.

[0187] The mixture was sintered at 850°C for 6 hours in an oxygen atmosphere, followed by sintering at 800°C for 9 hours to obtain the sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxides with an average particle size (D). 50 The thickness is 9.8 μm, and the composition is LiNi. 0.8833 Co 0.0298 Mn 0.0794 Al 0.0050 Nb 0.0010 Zr 0.0015 O2, and in the form of secondary particles aggregated from primary particles.

[0188] Co(OH)₂ was added to the lithium transition metal oxide in the secondary particulate form prepared above, such that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Y+Zr) (Co / (Ni+Co+Mn+Al+Y+Zr)) was 0.02, and 500 ppm of Al(OH)₃ was added relative to the total weight of the lithium transition metal oxide in the secondary particulate form prepared above, and the mixture was uniformly mixed to prepare a mixture. The mixture was sintered at 740°C for 3 hours in an oxygen atmosphere, and then sintered at 500°C for 3 hours to obtain a first coated product. The first coated product was ground at room temperature to achieve an average particle size (D). 50 A positive electrode active material with a particle size of 10.2 μm was prepared, wherein a coating containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the positive electrode active material including the coating is LiNi. 0.8641 Co 0.049 1Mn 0.0777 Al 0.0066 Nb 0.0010 Zr 0.0015 O2.

[0189] H3BO3 was added at a rate of 500 ppm relative to the total weight of the first coated product after grinding and mixed to prepare a mixture. The mixture was heat-treated in air at 330°C for 5 hours to obtain a second coated product. The second coated product was ground at room temperature to achieve an average particle size (D... 50A cathode active material with a particle size of 10.2 μm is prepared, wherein a coating containing Co, Al, and B is formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material including the coating is LiNi. 0.8602 Co 0.048 9Mn 0.0773 Al 0.0066 Nb 0.0010 Zr 0.0015 B 0.0045 O2.

[0190] Comparative Example 1

[0191] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.87 Co 0.05 Mn 0.08 (OH)2 transition metal complex hydroxide (D 50 Lithium (Li) was mixed with LiOH at a molar ratio of 10.2 μm to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) of 1.05. Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, Y2O3, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and then mixed to prepare the mixture.

[0192] The mixture was sintered at 780°C for 5 hours in an oxygen atmosphere to obtain a sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxide with an average particle size (D). 50 The thickness is 9.8 μm, and the composition is LiNi. 0.8635 Co 0.0496 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 O2, and in the form of secondary particles formed by primary particle aggregation. Subsequently, 100 parts by weight of the lithium transition metal oxide in the secondary particle form prepared above 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.

[0193] H3BO3 was added at a rate of 1000 ppm relative to the total weight of the lithium transition metal oxide to the dried product prepared above and mixed to prepare a mixture. The mixture was heat-treated in air at 300°C for 5 hours to obtain a coated product. The coated product was milled at room temperature to achieve an average particle size (D... 50A cathode active material with a particle size of 10.2 μm was prepared, wherein a boron-containing coating portion was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material, including the coating portion, is LiNi. 0.8558 Co 0.0492 Mn 0.0787 Al 0.0049 Y 0.0010 Zr 0.001 5B 0.0089 O2.

[0194] Comparative Example 2

[0195] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.87 Co 0.05 Mn 0.08 (OH)2 transition metal complex hydroxide (D 50 Lithium (Li) was mixed with LiOH to achieve a molar ratio (Li / (Ni+Co+Mn)) of 1.05 to that of the transition metal (Ni+Co+Mn). Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, Y2O3, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and then mixed to prepare the mixture.

[0196] The mixture was sintered at 780°C for 5 hours in an oxygen atmosphere to obtain a sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxide with an average particle size (D). 50 The thickness is 11.8 μm, and the composition is LiNi. 0.863 5Co 0.0496 Mn 0.0794 Al 0.0050 Y 0.0010 Zr 0.0015 O2, and in the form of secondary particles formed by primary particle aggregation. Subsequently, 100 parts by weight of the lithium transition metal oxide in the secondary particle form prepared above 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.

[0197] H3BO3 was added at a rate of 1000 ppm relative to the total weight of the lithium transition metal oxide to the dried product prepared above and mixed to prepare a mixture. The mixture was heat-treated in air at 300°C for 5 hours to obtain a coated product. The coated product was milled at room temperature to achieve an average particle size (D... 50A cathode active material with a particle size of 12.2 μm was prepared, wherein a boron-containing coating portion was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material, including the coating portion, is LiNi. 0.8558 Co 0.0492 Mn 0.0787 Al 0.0049 Y 0.0010 Zr 0.001 5B 0.0089 O2.

[0198] Comparative Example 3

[0199] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.89 Co 0.03 Mn 0.08 (OH)2 transition metal complex hydroxide (D 50 Li(OH)3 (10.2 μm) was mixed with LiOH to make the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) 1.04. Here, 1,470 ppm and 1,500 ppm of Al(OH)3 and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and they were mixed to prepare the mixture.

[0200] The mixture was sintered at 850°C for 6 hours in an oxygen atmosphere, followed by sintering at 800°C for 9 hours to obtain the sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxides with an average particle size (D). 50 The thickness is 9.8 μm, and the composition is LiNi. 0.8643 Co 0.0497 Mn 0.0795 Al 0.0050 Zr 0.0015 O2, and in the form of secondary particles aggregated from primary particles.

[0201] Co(OH)₂ was added to the lithium transition metal oxide in the secondary particulate form prepared above, such that the molar ratio of cobalt (Co) to metals other than lithium (Ni+Co+Mn+Al+Zr) (Co / (Ni+Co+Mn+Al+Zr)) was 0.02, and 500 ppm of Al(OH)₃ was added relative to the total weight of the lithium transition metal oxide in the secondary particulate form prepared above, and the mixture was uniformly mixed to prepare a mixture. The mixture was sintered at 740°C for 3 hours in an oxygen atmosphere, and then sintered at 500°C for 3 hours to obtain a first coated product. The first coated product was ground at room temperature to achieve an average particle size (D). 50A cathode active material with a particle size of 10.2 μm was prepared, wherein a coating containing Co and Al was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material including the coating is LiNi. 0.8455 Co 0.0686 Mn 0.0777 Al 0.0067 Zr 0.001 5O2.

[0202] H3BO3 was added at a rate of 500 ppm relative to the total weight of the first coated product after grinding and mixed to prepare a mixture. The mixture was heat-treated in air at 330°C for 5 hours to obtain a second coated product. The second coated product was ground at room temperature to achieve an average particle size (D... 50 A cathode active material with a particle size of 10.2 μm is prepared, wherein a coating containing Co, Al, and B is formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material including the coating is LiNi. 0.8380 Co 0.068 0Mn 0.0770 Al 0.0066 Zr 0.0015 B 0.0089 O2.

[0203] Comparative Example 4

[0204] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.94 Co 0.05 Mn 0.01 (OH)2 transition metal complex hydroxide (D 50 Li(OH)3 (14.5 μm) was mixed with LiOH to make the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) 1.02. Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, Y2O3, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and they were mixed to prepare a mixture.

[0205] The mixture was sintered at 730°C for 5 hours in an oxygen atmosphere to obtain a sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxide with an average particle size (D). 50 The thickness is 14.2 μm, and the composition is LiNi. 0.933 0Co 0.0496 Mn 0.0099 Al 0.0050 Y 0.0010 Zr0.0015 O2, and in the form of secondary particles formed by primary particle aggregation. Subsequently, 100 parts by weight of the lithium transition metal oxide in the secondary particle form prepared above 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.

[0206] H3BO3 was added at a rate of 1000 ppm relative to the total weight of the lithium transition metal oxide to the dried product prepared above and mixed to prepare a mixture. The mixture was heat-treated in air at 300°C for 5 hours to obtain a coated product. The coated product was milled at room temperature to achieve an average particle size (D... 50 A cathode active material with a particle size of 14.2 μm was prepared, wherein a boron-containing coating portion was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material, including the coating portion, is LiNi. 0.9246 Co 0.0492 Mn 0.0098 Al 0.0050 Y 0.0010 Zr 0.001 5B 0.0089 O2.

[0207] Comparative Example 5

[0208] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.94 Co 0.05 Mn 0.01 (OH)2 transition metal complex hydroxide (D 50 Lithium (Li) was mixed with LiOH at a molar ratio of 10.2 μm to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) to achieve a molar ratio of 1.02. Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, Y2O3, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and then mixed to prepare the mixture.

[0209] The mixture was sintered at 730°C for 5 hours in an oxygen atmosphere to obtain a sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxide with an average particle size (D). 50 The thickness is 9.8 μm, and the composition is LiNi. 0.9330 Co 0.0496 Mn 0.0099 Al 0.0050 Y 0.0010 Zr 0.0015O2, and in the form of secondary particles formed by primary particle aggregation. Subsequently, 100 parts by weight of the lithium transition metal oxide in the secondary particle form prepared above 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.

[0210] H3BO3 was added at a rate of 1000 ppm relative to the total weight of the lithium transition metal oxide to the dried product prepared above and mixed to prepare a mixture. The mixture was heat-treated in air at 300°C for 5 hours to obtain a coated product. The coated product was milled at room temperature to achieve an average particle size (D... 50 A cathode active material with a particle size of 10.2 μm was prepared, wherein a boron-containing coating portion was formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material, including the coating portion, is LiNi. 0.9246 Co 0.0492 Mn 0.0098 Al 0.0050 Y 0.0010 Zr 0.001 5B 0.0089 O2.

[0211] Comparative Example 6

[0212] The secondary particle form, composed of tens to hundreds of primary particles aggregated together, is Ni. 0.94 Co 0.05 Mn 0.01 (OH)2 transition metal complex hydroxide (D 50 Li(OH)3 (14.5 μm) was mixed with LiOH to make the molar ratio of lithium (Li) to transition metal (Ni+Co+Mn) (Li / (Ni+Co+Mn)) 1.04. Here, 1,470 ppm, 1,000 ppm, and 1,500 ppm of Al(OH)3, TiO2, and ZrO2 were added, respectively, relative to the total weight of the transition metal complex hydroxide, and they were mixed to prepare a mixture.

[0213] The mixture was sintered at 850°C for 6 hours in an oxygen atmosphere, followed by sintering at 800°C for 9 hours to obtain the sintered product. The sintered product was then ground at room temperature to prepare lithium transition metal oxides with an average particle size (D). 50 The thickness is 9.8 μm, and the composition is LiNi. 0.9330 Co 0.0496 Mn 0.0099 Al 0.0050 Ti 0.0010 Zr 0.0015 O2, and in the form of secondary particles aggregated from primary particles.

[0214] H3BO3 was added at a rate of 500 ppm relative to the total weight of the lithium transition metal oxide to the prepared secondary particulate lithium transition metal oxide and mixed to prepare a mixture. The mixture was heat-treated in air at 330°C for 5 hours to obtain a coated product. The coated product was then milled at room temperature to achieve an average particle size (D... 50 A cathode active material with a particle size of 9.8 μm is prepared, wherein a boron-containing coating is formed on a lithium transition metal oxide in the form of secondary particles aggregated from primary particles. The overall composition of the cathode active material including the coating is LiNi. 0.9287 Co 0.0494 Mn 0.0099 Al 0.0050 Ti 0.0010 Zr 0.0015 B 0.0045 O2.

[0215] Experimental Example

[0216] Experimental Example 1: Particle Analysis 1

[0217] The positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 6 were photographed using a scanning electron microscope (quanta 250FEG from FEI). The SEM images of Examples 1 and 2 are shown below. Figure 1 (A) and Figure 2 As shown in (A), the SEM images of Comparative Examples 1 to 6 are respectively as follows: Figure 3 (A) to Figure 8 As shown in (A). The average particle size of the primary particles present in each embodiment and comparative example was measured from the SEM images and is shown in Table 1 below.

[0218] In addition, the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 6 were subjected to ion milling and then photographed using a scanning electron microscope. The SEM images of Examples 1 and 2 are shown below. Figure 1 (B) and Figure 2 As shown in (B), the SEM images of Comparative Examples 1 to 6 are respectively as follows: Figure 3 (B) to Figure 8 As shown in (B). Figure 1 (B) to Figure 8 The white squares in (B) represent the number of primary particle sections identified within a unit area of ​​5 μm width × 5 μm length in the secondary particle section, as shown in Table 1 below, for secondary particle sections whose size is within the range of the average particle size (D50) of the secondary particles observed in the SEM image of the secondary particle section taken from the cross section of the positive electrode active material.

[0219] Furthermore, compared to the image analysis of the SEM images of Embodiments 1 and 2 of the present invention performed by the artificial intelligence model, segmented images were obtained by dividing the images into multiple lithium composite transition metal oxides, as shown in the figure. Figure 9 and 10 As shown, the segmentation images of Comparative Examples 1 and 2 are as follows: Figure 11 and 12 As shown.

[0220] [Table 1]

[0221]

[0222] refer to Figure 1 and Figure 2 As confirmed in Table 1, the positive electrode active materials of Examples 1 and 2 comprise secondary particles in which multiple primary particles aggregate, and the multiple primary particles have an average particle size of 1.5 μm to 5.0 μm as measured by SEM images. Furthermore, it was confirmed that the multiple primary particles include three or more disc-shaped primary particles. In this case, among the primary particles observed from SEM images of the surface or cross-section of the secondary particles, when an imaginary tangent with the most contact points is drawn for each of the boundary lines of two primary particles at an angle less than 45° relative to the major axis, and an imaginary line intersecting these two tangents is drawn, a disc-shaped primary particle refers to a primary particle with an interior angle on the same side ranging from 150° to 210°. For reference, in Figure 1 and Figure 2 In this study, when a light-colored imaginary tangent with the most contact points is drawn for each of the two boundary lines of a primary particle within an angle of 45° relative to the dark-colored major axis, the imaginary line (not shown) intersecting these two light-colored tangents satisfies an interior angle of 150° to 210° on the same side. Primary particles corresponding to this condition are defined as disc-shaped primary particles. Furthermore, it was confirmed that the minor axis of the disc-shaped primary particles is 0.3 μm or more, and the aspect ratio (major axis / minor axis) is 1.5 or more. Additionally, it was confirmed that the number of cross-sections of primary particles per unit area is in the range of 1 to 100. Simultaneously, compared to the positive electrode active materials of Comparative Examples 1, 2, 4, and 5, it was confirmed that the average particle size of the primary particles, measured by SEM images, is smaller, less than 500 nm.

[0223] Experimental Example 2: Particle Analysis 2

[0224] The positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 6 were photographed using a scanning electron microscope equipped with EBSD (quanta 250FEG from FEI).

[0225] Among them, for the electron backscatter diffraction (EBSD) pattern of the secondary particle cross-section observed in the SEM image of the secondary particle cross-section taken from the cross-section of the positive electrode active material of Comparative Example 4 (measured under the following conditions: accelerating voltage 20 kV, WD 16 mm, measurement magnification 5000x (16 μm width × 16 μm height), step size 0.025 μm), the electron backscatter diffraction (EBSD) pattern of the secondary particle cross-section with a size within the range of the average particle size (D50) was set in the central region and the outer peripheral region of the secondary particle cross-section, and presented in Figure 13 In (Comparative Example 4), the number of grain sections identified within the corresponding unit area and the degree of single crystal formation calculated according to Equation 1 below are listed together in Table 2 below.

[0226] [Equation 1]

[0227]

[0228] [Table 2]

[0229]

[0230] Referring to Table 2, for the positive electrode active materials of Examples 1 to 11, the number of grain cross-sectional areas per unit area was determined to be in the range of 1 to 150. Specifically, the number of grain cross-sections per unit area was confirmed to be in the range of 3 to 19. Furthermore, the single crystal formation degree was confirmed to be 0.15 μm. 3 above.

[0231] Experimental Example 3: Particle Analysis 3

[0232] From the SEM images obtained in Experimental Example 1, the single particle formation degree (Dv) corresponding to the volume diameter at which the cumulative volume distribution of primary particles in each embodiment and comparative example reached 50% was measured. 50 ), and display them in Table 3 below.

[0233] Specifically, the SEM images of the secondary particle surfaces of the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 to 5 were projected onto a two-dimensional plane. The area of ​​each primary particle was determined by the number of pixels corresponding to each of the n primary particles observed in the image. Then, assuming the surface of the primary particle is circular, that is, using the radius of a circle with an area equal to the surface area of ​​each primary particle as the surface radius of the primary particle, this radius was derived. Using this radius, the volume value was calculated according to Equation 5 below, and the degree of single particle formation (Dv) corresponding to the volume diameter at 50% of the cumulative volume distribution of the primary particles was calculated. 50 ), and display them in Table 3 below.

[0234] [Equation 5]

[0235] Volume = (4π / 3) × radius 3

[0236] [Table 3]

[0237] project <![CDATA[Degree of single particle formation (Dv 50 )(μm)]]> Example 1 2.12 Example 2 2.14 Comparative Example 1 1.05 Comparative Example 2 1.01 Comparative Example 3 2.21 Comparative Example 4 0.80 Comparative Example 5 0.87 Comparative Example 6 2.12

[0238] Referring to Table 3, for the positive electrode active materials of Examples 1 and 2, it was confirmed that the single particle formation degree was in the range of 1.2 μm to 3.8 μm.

[0239] Experimental Example 4: Particle Analysis 4

[0240] For the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 6, electron energy dispersive spectroscopy (ESCA) for chemical analysis was performed using a K-alpha XPS instrument from Thermo Fisher Scientific Inc. to analyze the elemental distribution in the Co and B coatings present on their surfaces. For depth profiling, etching was performed using an Ar ion source at a rate of 0.3 nm / 10 s, and the amounts (atomic %) of B and Co contained in the coatings were measured in thicknesses from 0 nm to 100 nm. The results are listed in Table 4 (B coating) and Table 5 (Co coating), respectively.

[0241] Electron probe microanalysis (EPMA) was performed on the positive electrode active materials of Examples 1 and 2 to determine the surface coating characteristics. First, a positive electrode slurry was prepared by mixing the positive electrode active material of Example 1, carbon black conductive agent, and PVDF binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 95:2:3. The prepared positive electrode slurry was coated onto one surface of an aluminum current collector, dried at 130°C, and then calendered to achieve an electrode porosity of 20% to prepare the positive electrode. To produce a flat EPMA profile analysis surface, Ar ion milling was performed on the positive electrode using a HITACHI IM-5000 instrument with an accelerating voltage of 6 kV to obtain the cross-section of the positive electrode sample. The cross-sectional image of the positive electrode sample was observed using a JEOL JXA-iHP200F instrument with an accelerating voltage of 15 kV and a probe current of 50 nA. Figure 14 and 15 As shown.

[0242] [Table 4]

[0243] Etching time (seconds) 0 10 30 50 100 200 300 500 1000 2000 3000 Example 1 10.3 10.2 9.1 9 6.5 4.4 3.3 2.8 1.8 1.3 1 Example 2 10.3 10.3 9.0 8.9 6.6 4.6 3.3 2.8 1.9 1.2 1 Comparative Example 1 16.4 17.5 15.1 14.8 11.8 8.9 7 5.9 3.5 2.4 1.5 Comparative Example 2 16 17.5 14.8 14.8 12 8.7 7.8 5.1 3 2 1 Comparative Example 3 10.9 11 9 8.5 6.1 4.9 3.7 2.8 2 1.5 0.8 Comparative Example 4 16 16.8 15.1 14.8 11.4 8.8 7.5 5.9 3.5 1.9 1.5 Comparative Example 5 15.4 16.4 15 14.8 11.2 8.7 7 5.5 3.8 2 1.1 Comparative Example 6 10.5 10.3 9.1 9.0 6.5 4.5 3.3 2.9 1.9 1.3 1.1

[0244] [Table 5]

[0245] Etching time (seconds) 0 10 30 50 100 200 300 500 1000 2000 3000 Example 1 1.8 2.6 4 5.1 6.2 4.7 3.5 2.5 1.1 0.9 0.8 Example 2 1.9 2.6 4.1 5.2 6.1 4.7 3.6 2.6 1.1 1.0 0.8 Comparative Example 1 0 0.1 0.1 0.3 0.3 0.3 0.4 0.8 0.9 0.9 0.6 Comparative Example 2 0 0.1 0.2 0.3 0.2 0.4 0.5 0.7 0.8 0.6 0.5 Comparative Example 3 1.7 2.5 3.6 4.4 5.2 4.8 4.1 2.6 1.3 0.9 0.8 Comparative Example 4 0.1 0.1 0.2 0.2 0.3 0.5 0.4 0.7 0.7 0.8 1.0 Comparative Example 5 0.1 0.2 0.1 0.2 0.3 0.3 0.4 0.7 0.7 0.8 1.0 Comparative Example 6 0 0.1 0.1 0.3 0.2 0.4 0.5 0.7 0.8 0.6 0.5

[0246] refer to Figure 1 and Figure 2 SEM images, Figure 14and 15 The EPMA images and Tables 4 and 5 confirm that, for the positive electrode active materials of Examples 1 and 2, coating portions containing Co and / or B are formed on the surface of the primary particles, the interface of the primary particles, and / or the surface of the secondary particles. Furthermore, it is confirmed that the coating portions are either island-shaped, formed on a portion of the surface of the primary particles, the interface of the primary particles, and / or the surface of the secondary particles, or coating-shaped, formed around the surface of the primary particles, the interface of the primary particles, and / or the surface of the secondary particles.

[0247] Experiment Example 5: Volume Cumulative Distribution Analysis

[0248] For the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 6, the D-value was measured using a particle size analyzer (PSD, Malvern Panalytical Ltd., Martensizer 3500). min D 50 D max Based on the mode of the volumetric cumulative distribution of particle size, and based on the y-value of the uppermost peak on the y-axis of the peak that appears at the mode of the volumetric cumulative distribution (P). 众数 ), θ L and θ R And calculate θ L -θ R And shown in Table 6.

[0249] Additionally, the skewness value (S) is calculated using Equation 3 below, and the y-value (P) of the skewness value (S) is calculated as the sum of the y-values ​​of the peaks at the uppermost point of the y-axis of the peaks appearing according to the mode of the volumetric cumulative distribution. 众数 The ratio of S / P 众数 ), and list them together in Table 6 below.

[0250] [Equation 3]

[0251] Skewness value (S) = 3 × (volume average particle size - (D50)) / standard deviation of positive electrode active material particle size

[0252] [Table 6]

[0253]

[0254]

[0255] Referring to Table 6, for the positive electrode active materials of Examples 1 and 2, D was confirmed. 50 Within the range of 7.0 μm to 20.0 μm. Furthermore, it was confirmed that (θ) L -θ RThe values ​​range from 6 to 20. Furthermore, it was confirmed that the frequency distribution plot showing the cumulative volume distribution, measured using a laser diffraction particle size analyzer, exhibited a positive skewness, where the x-axis values ​​represent the particle size increasing linearly from left to right, and the y-axis values ​​represent the volume distribution increasing from bottom to top.

[0256] Experiment Example 6: Measurement of Rolling Density

[0257] Using an automatic pelletizer (Auto Pellet Press, Carver, 3887.4), the thickness zero point of a circular particle holder with a diameter of 13 mm was adjusted using a cylindrical die. Subsequently, 3 g of each of the positive electrode active material prepared in Examples 1 and 2 and Comparative Examples 1 to 6 were placed into the circular particle holder, and a force was applied up to 9,000 kgf to measure the thickness of the formed particles. The particle volume was then calculated using Equation 4 below, and the rolling density was calculated using Equation 2 below. The results are shown in Table 7 below.

[0258] [Equation 4]

[0259] Particle volume (cm) 3 ) = π (radius of the circular particle container) 2 ×particle thickness

[0260] [Equation 2]

[0261] Rolled density (g / cm³) 3 = Weight of positive electrode active material (g) / Particle volume (cm³) 3 )

[0262] [Table 7]

[0263] project <![CDATA[Rolling density (g / cm 3 )]]> Example 1 3.65 Example 2 3.65 Comparative Example 1 3.27 Comparative Example 2 3.30 Comparative Example 3 3.69 Comparative Example 4 3.49 Comparative Example 5 3.46 Comparative Example 6 3.6

[0264] Referring to Table 7, the rolling density of the positive electrode active materials in Examples 1 and 2 was confirmed to be 3.60 g / cm³. 3 above.

[0265] Experiment Example 7: BET Specific Surface Area Measurement

[0266] Specific surface area was measured using nitrogen adsorption and desorption methods. Specifically, after measuring the weight of the empty battery cell, 3g of each of the positive electrode active materials prepared in Examples 1 to 11 and Comparative Examples 1 to 13 were taken and pretreated at 130°C for 3 hours. After measuring the weight of the battery cell after the pretreatment process, a Dewar flask containing liquid nitrogen was prepared, and the battery cell was connected to it. Under a nitrogen atmosphere, the Brunauer-Emmett-Teller (BET) specific surface area was measured based on the amount of nitrogen adsorbed using a gas adsorption analyzer (Micromeritics TriStarr II), and the results are shown in Table 8 below.

[0267] [Table 8]

[0268] project <![CDATA[Specific surface area (m 2 / g)]]> Example 1 0.303 Example 2 0.295 Comparative Example 1 0.504 Comparative Example 2 0.592 Comparative Example 3 0.287 Comparative Example 4 0.631 Comparative Example 5 0.729 Comparative Example 6 0.303

[0269] Referring to Table 8, for the positive electrode active materials of Examples 1 and 2, the BET specific surface area was confirmed to be 0.20 m². 2 / g to 0.35m 2 Within the range of / g.

[0270] Experiment Example 8: Fabrication and Charge / Discharge Evaluation of Button-Type Semi-Cells

[0271] A positive electrode slurry was prepared by mixing 95 parts by weight of each positive electrode active material prepared in Examples 1 and 2 and Comparative Examples 1 to 6, 2 parts by weight of a conductive agent (Denka Company Limited, FX35), and 3 parts by weight of a binder (Kureha Corporation, KF9709) in an N-methylpyrrolidone (NMP) solvent. The positive electrode slurry prepared above was coated on one surface of a 20 μm thick aluminum current collector and rolled to obtain a positive electrode active material layer with a porosity of 24% by volume.

[0272] A lithium metal electrode was used as the negative electrode, and an electrode assembly was fabricated by placing a porous polyethylene membrane between the positive and negative electrodes. The electrode assembly was then placed in a battery case and an electrolyte solution was injected to fabricate a lithium secondary battery. In this case, the electrolyte solution was prepared by dissolving 1M LiPF6 in an organic solvent, wherein ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4.

[0273] The lithium secondary batteries prepared above, including those using the positive electrode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 6, were charged to 4.25V at a constant current of 0.1C in constant current / constant voltage (CC / CV) mode at 25°C (termination current 0.05C), and then discharged to 2.5V in CC mode. The charging and discharging capacities were measured and are shown in Table 3 below. In this case, 1C was set to 200mA / g.

[0274] In addition, the lithium secondary battery prepared above was charged to 4.25V at 0.5C constant current in CC-CV mode at 45°C (with a termination current of 0.05C), and the lithium secondary battery was discharged to 2.5V at 1.0C constant current in CC mode as one cycle. This cycle was repeated for 50 cycles. The percentage of the discharge capacity of the 50th cycle relative to the discharge capacity of the 1st cycle was set as the capacity retention rate, and the capacity retention rates are listed in Table 9 below.

[0275] [Table 9]

[0276]

[0277] Experimental Example 9: High-rate discharge capacity assessment

[0278] Each lithium secondary battery prepared in Experimental Example 8 was charged at 25°C in CC / CV mode with a constant current of 0.5C to 4.25V (termination current of 0.05C), and then discharged in CC mode with a constant current of 0.1C to 2.5V. The discharge capacity was measured. Additionally, each lithium secondary battery was charged at 25°C in CC / CV mode with a constant current of 0.5C to 4.25V (termination current of 0.05C), and then discharged in CC mode with a constant current of 1.0C to 2.5V. The discharge capacity was measured. Similarly, each lithium secondary battery was charged at 25°C in CC / CV mode with a constant current of 0.5C to 4.25V (termination current of 0.05C), and then discharged in CC mode with a constant current of 2.0C to 2.5V. The percentage of each discharge capacity relative to the discharge capacity after charging at 0.5C and discharging at 0.1C is shown in Table 10 below.

[0279] [Table 10]

[0280]

[0281]

[0282] Referring to Tables 9 and 10, for batteries containing the positive electrode active materials of Examples 1 and 2, it was confirmed that they exhibit high high-temperature capacity retention, low DC resistance, and excellent rate performance. Conversely, it was confirmed that batteries containing materials without M... 3 The positive electrode active materials of Comparative Examples 1 to 5 exhibit higher DC resistance, lower high-temperature capacity retention, and poorer rate performance; including those without a coating containing Co and B (even if they simultaneously contain Al, Zr, and M). 3 The positive electrode active material of Comparative Example 6 has a larger DC resistance, lower high-temperature capacity retention, and poor rate performance compared to the battery of Comparative Example 6.

[0283] These results confirm that the positive electrode active material of the present invention is a high-Ni positive electrode active material, which can simultaneously solve the problems of typical secondary particles and single particles. In particular, by realizing the positive electrode active material as a secondary particle in which the primary particle size is on the micrometer scale, the positive electrode active material of the present invention can improve the energy density through excellent density characteristics, as well as improve the life of lithium secondary batteries and reduce the amount of gas generated, and other cell characteristics.

Claims

1. A positive electrode active material, which comprises secondary particles in which a plurality of primary particles are aggregated, in, the plurality of primary particles having an average particle diameter of 1.5 μm to 5.0 μm as measured by a scanning electron microscope (SEM) image, the particle diameter of the primary particles being the particle diameter with respect to the major axis of the primary particles, The positive electrode active material includes aluminum (Al), zirconium (Zr), and M. 3 Lithium transition metal composite oxides, M 3 It is a metallic element with an oxidation state of +4 or higher, and the positive electrode active material comprising a coating portion containing cobalt (Co) and boron (B).

2. The positive electrode active material as described in claim 1, wherein, M 3 It is selected from at least one of the group consisting of titanium (Ti), tantalum (Ta), tungsten (W), vanadium (V), molybdenum (Mo) and niobium (Nb).

3. The positive electrode active material of claim 1, comprising: Al in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal complex oxide, Zr in an amount of 500 ppm to 3,000 ppm relative to the total weight of the lithium transition metal complex oxide, and M in an amount of 100 ppm to 2,000 ppm relative to the total weight of the lithium transition metal complex oxide. 3 .

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

5. The positive electrode active material according to claim 1, which comprises a lithium transition metal composite oxide in which the content of nickel in the total transition metals is 60 mol% or more.

6. The positive electrode active material according to claim 1, which comprises a lithium transition metal composite oxide having an average composition represented by the following formula 1: [Formula 1] Li x Ni a Co b Mr c M 1 d O2 in, In formula 1, M 1 The element is selected from at least one of the following groups: aluminum (Al), zirconium (Zr), boron (B), tungsten (W), molybdenum (Mo), chromium (Cr), niobium (Nb), magnesium (Mg), hafnium (Hf), tantalum (Ta), lanthanum (La), titanium (Ti), strontium (Sr), barium (Ba), cerium (Ce), vanadium (V), fluorine (F), phosphorus (P), sulfur (S), and yttrium (Y). 0.9 ≤ x ≤ 1.3, 0.6 ≤ a < 1.0, 0 < b < 0.4, 0 < c < 0.4, 0 ≤ d ≤ 0.2 and a + b + c + d = 1 are satisfied.

7. The positive electrode active material as described in claim 1, wherein, The plurality of primary particles include single crystal primary particles.

8. The positive electrode active material as described in claim 1, wherein, Based on the cumulative volume distribution measured using a laser diffraction particle size analyzer, the average particle size (D) of the secondary particles is... 50 The range is from 7.0 μm to 20.0 μm.

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

10. A lithium secondary battery, comprising: The positive electrode according to claim 9; a negative electrode; a separator disposed between the positive electrode and the negative electrode, and an electrolyte.

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