JP-2026514222-A - Positive electrode active material, positive electrode, and lithium secondary battery

Abstract

The present invention relates to a positive electrode active material, and more particularly to a positive electrode and lithium secondary battery containing the same, which can simultaneously solve the problems of both secondary particles and single particles in the conventional system. The positive electrode active material contains particles such as single particles as primary particles, and also contains secondary particles formed by the aggregation of multiple primary particles. This allows for improved cell characteristics such as increased lifespan and reduced gas generation in lithium secondary batteries, as well as superior density characteristics and improved energy density.

Inventors

• ジュ・キョン・ファン
• ジン・ホ・ジョン
• ミュン・ギ・ジョン
• ジ・ユン・イ
• ヒョン・モ・リュ
• クク・ジン・ホ
• ジュン・ウク・イ
• サン・ウン・バク
• ジョン・ヒュク・キム

Assignees

• エルジー・ケム・リミテッド

Dates

Publication Date

20260507

Application Date

20240429

Priority Date

20230428

Claims (9)

1. It contains secondary particles formed by the aggregation of multiple primary particles, The aforementioned multiple primary particles have an average particle size of 1.5 μm or more and 5.0 μm or less, as measured from SEM images. The particle size of the primary particle is the particle size based on the major axis of the primary particle. A positive electrode active material in which, when the volume value is calculated from the following formula 5 for each primary particle observed from an SEM image of the surface of a secondary particle (measurement magnification 3,000x), the degree of single-particle formation (Dv 50 ) corresponding to the diameter of the volume at the point where the cumulative volume distribution of the primary particles reaches 50% is between 1.2 μm and 3.8 μm. In the above formula 5, Radius is the radius of the primary particle's surface, assuming the primary particle's surface is circular, as observed from an SEM image of the secondary particle's surface (measurement magnification 3,000x).
2. The positive electrode active material according to claim 1, wherein the degree of single particle formation (Dv 50 ) is 1.65 μm or more and 3.55 μm or less.
3. The positive electrode active material according to claim 1, comprising a lithium transition metal composite oxide containing nickel, cobalt, and manganese.
4. The positive electrode active material according to claim 1, comprising a lithium transition metal composite oxide containing 60 mol% or more nickel among the total transition metals.
5. The positive electrode active material according to claim 1, comprising a lithium transition metal composite oxide having an average composition represented by the following chemical formula 1. [Chemical formula 1] Li x Ni a Co b Mn c M 1 d O 2 In the aforementioned chemical formula 1, M1 is one or more elements selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, V, F, P, S, and Y. 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.
6. The cathode active material according to claim 1, wherein the plurality of primary particles include single-crystal primary particles.
7. The positive electrode active material according to claim 1, wherein the secondary particles have an average particle size ( D50 ) of 7.0 μm or more and 20.0 μm or less, determined by the volume cumulative distribution measured using a laser diffraction particle size analyzer.
8. A positive electrode comprising the positive electrode active material described in any one of claims 1 to 7.
9. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte, as described in claim 8.

Description

This application claims priority under Korean Patent Application No. 10-2023-0056231 dated April 28, 2023, and Korean Patent Application No. 10-2024-0057193 dated April 29, 2024, and all content disclosed in the documents of said Korean patent applications is incorporated herein by reference. This invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. Recently, advancements in technologies such as electric vehicles have led to increased demand for high-capacity secondary batteries. Consequently, research into high-nickel (High Ni) cathode active materials with superior capacity characteristics is being actively pursued. In high-nickel positive electrode active materials, where primary particles aggregate to form secondary particles, structural degeneration occurs during charging and discharging of lithium-ion batteries. However, relative changes in the lattice structure constant, i.e., significant volume changes within the unit cell, also occur. Such volume changes can cause cracks within the positive electrode active material. Furthermore, cracks can also occur in the positive electrode active material due to pressure during electrode rolling. The cracks that occur in the high-nickel cathode active material in this way worsen during the charging and discharging process of the lithium secondary battery. This can prevent the electrolyte from reaching the cracks, or cause them to act as voids that reduce conductivity, thereby degrading the lifespan of the lithium secondary battery or increasing its resistance. To minimize crack formation in such secondary particle structures, attempts have been made to manufacture cathode active materials in single-particle form. However, such single-particle cathode active materials suffer from non-uniform particle size distribution, resulting in a large particle size distribution after pulverization. Furthermore, single-particle cathode active materials have a small specific surface area and weak cell resistance characteristics. Therefore, there is a need to develop cathode active materials that can simultaneously solve both the conventional secondary particle problem and the single-particle problem. On the other hand, Korean Patent Publication No. 10-1785262 (Patent Document 1) discloses large-particle secondary particles containing aggregated primary particles, where the secondary particles contain nickel-based lithium transition metal oxides, the average particle size of the primary particles is 3 to 5 μm, and the average particle size of the secondary particles is 10 to 20 μm. Such large-particle secondary particles, by containing primary particles with an average particle size at the micron level, can improve rolling density and minimize cracks caused by rolling, and the structure of the secondary particles can improve specific surface area and enhance cell properties. To manufacture a positive electrode active material in the form of secondary particles, where the size of the primary particles is at the micron level, it is necessary to perform heat treatment at a higher temperature than for secondary particles, where the size of the primary particles is at the submicron level (less than 1 μm), as disclosed in Patent Document 1. However, the higher the heat treatment temperature, the more the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure, causing a decrease in crystallinity, which in turn degrades the performance of the positive electrode active material. In particular, the degeneration of the layered structure of the lithium transition metal composite oxide into a rock salt structure at high heat treatment temperatures is weakest with respect to nickel. Therefore, the degeneration becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the positive electrode active material is high. Therefore, conventionally, as a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level, it has only been possible to apply it to mid-nickel (Mid Ni) positive electrode active materials where the nickel content among the transition metals in the lithium transition metal composite oxide is at the 50 mol level, as described in Patent Document 1. For high-nickel (High Ni) positive electrode active materials, which have a high nickel content among the transition metals in the lithium transition metal composite oxide and excellent capacitance characteristics, it has been impossible to manufacture a positive electrode active material in the form of secondary particles with primary particle sizes at the micron level. KR10-1785262 B1KR10-2017-0119573A (A) SEM image of the positive electrode active material and (B) SEM image of the cross-section of the positive electrode active material in Example 1.(A) SEM image of the positive electrode active material