KR-20260062885-A - POSITIVE ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY

Abstract

The present invention relates to a positive electrode active material, and to a positive electrode active material capable of simultaneously solving the problems of conventional secondary particles and single particles, comprising a particle similar to a conventional single particle as a primary particle, and comprising a plurality of secondary particles aggregated from the primary particles, wherein the plurality of primary particles have an average particle size measured from an SEM image of 1.0 μm or more and 3.0 μm or less, and the particle size of the primary particles is a particle size based on the major axis of the primary particles, and satisfies Equation 1 described in the present specification, thereby improving the capacity characteristics, high-temperature life characteristics, and rate characteristics of a lithium secondary battery, and to a positive electrode including the same and a lithium secondary battery.

Inventors

• 류현모
• 이정욱
• 정진후
• 황주경
• 이지영
• 허국진
• 박상은
• 김종혁

Assignees

• 주식회사 엘지화학

Dates

Publication Date

20260507

Application Date

20251029

Priority Date

20241029

Claims (11)

1. It includes secondary particles formed by the aggregation of multiple primary particles, and The plurality of primary particles have an average particle size of 1.0 μm or more and 3.0 μm or less as measured from SEM images, and the particle size of the primary particles is the particle size based on the major axis of the primary particles, and It comprises a lithium transition metal complex oxide containing 60 mol% or more of nickel among the total transition metals, and A positive electrode active material whose pore distribution graph measured by the mercury intrusion method satisfies the following Equation 1: [Equation 1] 0.8 ≤ y max (5000≤x≤8000)/y max (2000≤x<5000) ≤ 5 In the above Equation 1, x is the pore size (unit: nm), and y is log differential intrusion (unit: mL/g).
2. In claim 1, The above plurality of primary particles include disk-type primary particles, and The above-mentioned disk-shaped primary particle is a positive electrode active 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.
3. In claim 1, The above plurality of primary particles include disk-type primary particles, and The above disk-shaped primary particle is a positive electrode active material in which, for a primary particle observed from an SEM image of the surface or cross-section of a 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, and the area ratio of the (003) plane among the crystal planes of the surface portion of the primary particle is the largest.
4. In claim 1, A positive electrode active material comprising a lithium transition metal complex oxide containing nickel, cobalt, and manganese.
5. In claim 1, A positive electrode active material comprising a lithium transition metal complex oxide having an average composition represented by the following chemical formula 1: [Chemical Formula 1] Li x Ni a Co b Mn c M 1 d O 2 In the above chemical formula 1, 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≤x≤1.3, 0.6≤a<1.0, 0<b<0.4, 0<c<0.4, 0≤d≤0.2, a+b+c+d=1.
6. In claim 1, The above plurality of primary particles is a positive active material comprising single-crystal primary particles.
7. In claim 1, The above secondary particles are positive active materials 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.
8. In claim 1, The above plurality of primary particles is a positive active material comprising three or more disk-type primary particles.
9. In claim 1, A positive active material having a rolled density of 3.60 g/cm³ or higher calculated by the following Equation 2, when a positive active material is fed into a cylindrical mold with a diameter of 13 mm using an automatic pellet press and a force is applied until a force equivalent to 9,000 kgf is formed to form a pellet: [Equation 2] Rolled density (g/ cm³ ) = Weight of anode active material (g) / Pellet volume ( cm³ ).
10. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 9.
11. A lithium secondary battery comprising a positive electrode according to claim 10; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

Description

Positive ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY The present invention relates to a positive electrode active material, a positive electrode containing 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. Figure 1 is an SEM image of a positive electrode active material according to Example 1 of the present invention. Figure 2 is an SEM image of a positive electrode active material according to Example 2 of the present invention. Figure 3 is an SEM image of a positive electrode active material according to Example 3 of the present invention. Figure 4 is an SEM image of a positive electrode active mater