KR-20260062887-A - POSITIVE ELECTRODE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

Abstract

The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery. The cathode material comprises a first cathode active material in the form of secondary particles having a primary particle size of 1.5 μm or more and 5.0 μm or less, and a second cathode active material in the form of secondary particles having an average particle diameter (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer smaller than that of the first cathode active material and a primary particle size of less than 1.0 μm. The plurality of primary particles of the first cathode active material comprises disk-type primary particles. Regarding the disk-type primary particles, in the case of primary particles observed from an SEM image of the surface or cross-section of the secondary particles, when a virtual tangent line having the most contact points is drawn for each of the two boundary lines of the primary particles existing within an angle of 45° or less with respect to the major axis direction, and a single virtual line crossing the two tangent lines is drawn, the same internal angle is 150 By satisfying the conditions of being greater than ° and less than 210 °, having a short diameter of 0.3 μm or more, and an aspect ratio (long diameter/short diameter) of 1.5 or more, not only is the rolling density high, but the energy density of the electrode and battery containing it can also be improved.

Inventors

• 양정진
• 정진후
• 이경록
• 이지영
• 박상은
• 김종혁

Assignees

• 주식회사 엘지화학

Dates

Publication Date

20260507

Application Date

20251029

Priority Date

20241029

Claims (12)

1. A first positive active material comprising a plurality of secondary particles aggregated from a plurality of primary particles, wherein the plurality of primary particles have an average particle size of 1.5 μm or more and 5.0 μm or less as measured from an SEM image, and the particle size of the primary particles is the particle size based on the major axis of the primary particles; and A cathode material comprising: a second cathode active material comprising a plurality of primary particles aggregated into secondary particles, wherein the plurality of primary particles have an average particle size of less than 1.0 μm as measured from an SEM image, and the particle size of the primary particles is the particle size based on the major axis of the primary particles; The first positive active material has a larger average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer than the second positive active material. The plurality of primary particles of the first positive active material include disk-type primary particles, and The above-mentioned disc-shaped primary particle is a cathode material in which, regarding the primary particle observed from an SEM image of the surface or cross-section of the secondary particle, when a virtual tangent line having the most contact points is drawn for each of the two boundary lines of the primary particle existing within an angle of 45° or less with respect to the major axis direction, and a virtual line crossing the two tangent lines is drawn, the internal angle on the same side is 150° or more and 210° or less, the minor diameter is 0.3 μm or more, and the aspect ratio (major axis/minor diameter) is 1.5 or more.
2. In claim 1, The above-mentioned first positive active material is a positive material comprising 10% or more and 90% or less by weight relative to the total weight of the first positive active material and the second positive active material.
3. In claim 1, The above-mentioned disk-shaped primary particle is an anode material having a short diameter of 0.7 μm or more.
4. In claim 1, The above-mentioned first positive active material is a positive material comprising a first lithium transition metal composite oxide containing 60 mol% or more of nickel among the total transition metals.
5. In claim 4, The above-mentioned first lithium transition metal composite oxide is a cathode material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li x1 Ni a1 Co b1 Mn c1 M 1 d1 O 2 In the above chemical formula 1, M1 is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, S, and Y, and 0.9≤x1≤1.3, 0.6≤a1<1.0, 0<b1<0.4, 0<c1<0.4, 0≤d1≤0.2, a1+b1+c1+d1=1.
6. In claim 1, The above-mentioned second positive active material is a positive material comprising a second lithium transition metal composite oxide containing 60 mol% or more of nickel among the total transition metals.
7. In claim 6, The above-mentioned second lithium transition metal composite oxide is a cathode material having a composition represented by the following chemical formula 2: [Chemical Formula 2] Li x2 Ni a2 Co b2 Mn c2 M 2 d2 O 2 In the above chemical formula 2, M 2 is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, S, and Y, and 0.9≤x2≤1.3, 0.6≤a2<1.0, 0<b2<0.4, 0<c2<0.4, 0≤d2≤0.2, a2+b2+c2+d2=1.
8. In claim 1, A cathode material in which the plurality of primary particles of the first cathode active material include single-crystal primary particles.
9. In claim 1, The first positive active material is a positive material having an average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer of 7.0 μm or more and 20.0 μm or less.
10. In claim 1, The above second positive active material is a positive material having an average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer of 2.0 μm or more and 6.0 μm or less.
11. A cathode comprising a cathode material according to any one of claims 1 to 10.
12. A lithium secondary battery comprising a positive electrode according to claim 11; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

Description

Positive ELECTRODE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery. With the recent technological advancements in electric vehicles and the like, the demand for high-capacity secondary batteries is increasing, and accordingly, research on high-nickel (High Ni) cathode active materials with excellent capacity characteristics is actively underway. High-nickel cathode active materials formed with a secondary particle structure in which primary particles are aggregated undergo structural degradation during the charging and discharging of lithium secondary batteries, but also experience relatively significant changes in lattice structure constants, that is, changes in volume within the unit cell. These volume changes cause cracks within the cathode active material. Additionally, cracks may also occur within the cathode active material due to pressure during electrode rolling. The cracks generated in this way within the high-nickel cathode active material become more severe during the charging and discharging process of the lithium secondary battery. Consequently, they act as voids that prevent the electrolyte from reaching or reduce conductivity, thereby degrading the lifespan characteristics of the lithium secondary battery or acting as a factor in increasing resistance. Attempts are being made to manufacture single-particle cathode active materials as a means to minimize crack formation in such secondary particle structures. However, such single-particle cathode active materials have a problem in that the particle size distribution of the single-particle cathode active material obtained after grinding is large due to the non-uniform particle sizes. In addition, single-particle cathode active materials have a low specific surface area, which makes them vulnerable to cell resistance characteristics. Therefore, there is a need for the development of a positive electrode active material that can simultaneously solve the problems of conventional secondary particles and single particles. Meanwhile, Korean Registered Patent Publication No. 10-1785262 (Patent Document 1) discloses large-diameter secondary particles comprising primary particles aggregated into secondary particles, wherein the secondary particles comprise nickel-based lithium transition metal oxides, the average particle size of the primary particles is 3 to 5 μm, and the average particle size of the secondary particles is 10 to 20 μm. By including primary particles with an average particle size at the micron level, these large-diameter secondary particles can improve rolling density to minimize cracks caused by rolling, etc., and improve cell characteristics by improving the specific surface area through the secondary particle structure. In order to manufacture a cathode active material in the form of secondary particles with a primary particle size at the micron level, as disclosed in Patent Document 1, it is necessary to perform heat treatment at a higher temperature than that for secondary particles with a primary particle size of less than 1 μm at the submicron level. However, as the heat treatment temperature increases, the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure, which causes a decrease in crystallinity and, consequently, a decrease in the performance of the cathode active material. In particular, since nickel is most susceptible to the degeneration of the layered structure of the lithium transition metal composite oxide into a rock salt structure at high heat treatment temperatures, the degeneration becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the cathode active material increases. Therefore, conventionally, as a cathode active material in the form of secondary particles with a primary particle size at the micron level, it could only be applied to a Mid Ni cathode active material in which the nickel content among the transition metals of the lithium transition metal composite oxide is at the 50 mol% level, as in Patent Document 1, and it was not possible to manufacture a cathode active material in the form of secondary particles with a primary particle size at the micron level for a High Ni cathode active material in which the nickel content among the transition metals of the lithium transition metal composite oxide is high and has excellent capacity characteristics. Accordingly, the inventors of the present invention have developed a positive electrode active material (single particle cluster) that can simultaneously solve the problems of conventional secondary particles and single particles in a high nickel (High Ni) positive electrode active material. Additionally, the inventors of the present invention confirmed that when the above single particle cluster is used as a cathode