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CN-122029644-A - Positive electrode active material, positive electrode comprising same, and lithium secondary battery

CN122029644ACN 122029644 ACN122029644 ACN 122029644ACN-122029644-A

Abstract

The present invention relates to a positive electrode active material, a method of preparing the same, and a lithium secondary battery including the same. Specifically, the positive electrode active material of the present invention comprises a lithium nickel-based oxide having a nickel content of 70 mol% or more in all metal elements except lithium, a first coating layer formed on the lithium nickel-based oxide, and a second coating layer formed on the first coating layer, wherein the first coating layer comprises a coating element M1 (M1 is at least one selected from the group consisting of nickel (Ni), cobalt (Co) and aluminum (Al)), the second coating layer comprises a coating element M2 (M2 is titanium (Ti)), and the content of titanium contained in the second coating layer may be 0.7 to 3.3 atomic% as measured by X-ray photoelectron spectroscopy (XPS) based on the total content of Ni, co, lithium (Li) and oxygen (O) contained in the lithium nickel-based oxide.

Inventors

  • WU XIUJUAN
  • Lu Enshuai
  • HUANG JINTAI
  • JIN HENGYI
  • LI XIZHEN

Assignees

  • 株式会社LG新能源

Dates

Publication Date
20260512
Application Date
20241015
Priority Date
20231019

Claims (20)

  1. 1. A positive electrode active material, comprising: A lithium nickel-based oxide having a nickel content of 70 mol% or more in all metal elements except lithium, a first coating layer formed on the lithium nickel-based oxide, and a second coating layer formed on the first coating layer, Wherein the first coating layer contains a coating element M1, M1 is at least one selected from the group consisting of nickel (Ni), cobalt (Co) and aluminum (Al), The second coating comprises a coating element M2, M2 is titanium (Ti), and The content of titanium contained in the second coating layer measured by X-ray photoelectron spectroscopy (XPS) is 0.7 to 3.3 at% based on the total content of Ni, co, lithium (Li) and oxygen (O) contained in the lithium nickel-based oxide measured by XPS.
  2. 2. The positive electrode active material according to claim 1, wherein the lithium nickel-based oxide is represented by formula 1: [ 1] Li a Ni b Co c M ' d M '' e O 2 Wherein, in the formula 1, M ' is manganese (Mn), aluminum (Al) or a combination thereof, M '' is at least one selected from the group consisting of Al, zirconium (Zr), tungsten (W), titanium (Ti), magnesium (Mg), calcium (Ca) and strontium (Sr), and 0.8≤a≤ 1.2,0.7≤b <1.0, 0≤c <0.3, 0≤d <0.3, 0≤e≤0.2.
  3. 3. The positive electrode active material according to claim 1, wherein the lithium nickel-based oxide is in the form of single particles composed of one primary particle or quasi-single particles as an aggregate of 30 or less primary particles.
  4. 4. The positive electrode active material according to claim 1, wherein an average particle diameter (D 50 ) of the lithium nickel-based oxide is 1.0 μm to 8.0 μm.
  5. 5. The positive electrode active material according to claim 1, wherein the first coating layer is continuously coated on the surface of the lithium nickel-based oxide.
  6. 6. The positive electrode active material of claim 1, wherein the first coating layer comprises Al 2 O 3 and Co 3 O 4 .
  7. 7. The positive electrode active material according to claim 1, wherein the second coating layer is discontinuously distributed on the surface of the first coating layer.
  8. 8. The positive electrode active material according to claim 1, wherein the second coating layer comprises titanium dioxide (TiO 2 ).
  9. 9. The positive electrode active material according to claim 8, wherein the average particle diameter (D 50 ) of the titanium oxide (TiO 2 ) is 20 nm to 150 nm.
  10. 10. The positive electrode active material according to claim 8, wherein the content of the titanium oxide (TiO 2 ) is 1000 ppm to 2000 ppm based on the total amount of the positive electrode active material.
  11. 11. The positive electrode active material according to claim 1, wherein the first and second coating layers are contained in an amount of 2.3 to 2.5 wt% based on the total amount of the positive electrode active material.
  12. 12. The positive electrode active material according to claim 1, wherein the weight ratio of the first coating layer to the second coating layer is contained in a range of 1:0.04 to 1:0.1.
  13. 13. The positive electrode active material according to claim 1, wherein the content of titanium contained in the second coating layer measured by XPS is 0.7 to 3.0 at% based on the total content of Ni, co, li, and oxygen (O) contained in the lithium nickel-based oxide measured by XPS.
  14. 14. The positive electrode active material according to claim 1, wherein the positive electrode active material has a maximum heat flow of 11W/g or less as measured by Differential Scanning Calorimetry (DSC).
  15. 15. A method of preparing the positive electrode active material of claim 1, the method comprising: Preparing a transition metal precursor containing nickel (Ni), cobalt (Co) and manganese (Mn) and having a nickel content of 70 mol% or more in all metal elements; Mixing the transition metal precursor with a lithium-containing raw material, and performing primary sintering to form lithium nickel oxide; mixing the lithium nickel oxide with an aluminum precursor and a cobalt precursor, and performing secondary sintering to form a first coating layer containing a coating element M1 on the lithium nickel oxide, M1 being at least one selected from Ni, co and aluminum (Al), and The lithium nickel-based oxide having the first coating layer formed thereon is mixed with a titanium precursor and subjected to three times of sintering, thereby forming a second coating layer containing a coating element M2 on the surface of the first coating layer, M2 being titanium (Ti).
  16. 16. The method of claim 15, wherein the transition metal precursor is represented by formula 2: [ 2] Ni x Co y Mn z M 3 q (OH) 2 Wherein, in the formula 2, M 3 is at least one selected from the group consisting of manganese (Mn), aluminum (Al), zirconium (Zr), tungsten (W), titanium (Ti), magnesium (Mg), calcium (Ca) and strontium (Sr), and 0.7≤x≤1.0, 0< y≤0.3, 0< z <0.3, 0≤q≤0.2.
  17. 17. The method of claim 15, wherein the primary sintering is performed at a temperature of 800 ℃ to 890 ℃.
  18. 18. The method of claim 15, wherein the secondary sintering is performed at a temperature of 600 ℃ to 790 ℃.
  19. 19. The method of claim 15, wherein the three sintering is performed at a temperature of 600 ℃ to 700 ℃.
  20. 20. The method of claim 15, wherein the mixed molar ratio of lithium nickel-based oxide with the first coating layer formed to the titanium precursor is 100:0.1 to 100:0.3.

Description

Positive electrode active material, positive electrode comprising same, and lithium secondary battery Cross Reference to Related Applications The present application claims priority from korean patent application No. 10-2023-0140699 filed on day 19 of 10 in 2023 and korean patent application No. 10-2024-0139856 filed on day 14 of 10 in 2024, the disclosures of which are incorporated herein by reference. Technical Field The present invention relates to a positive electrode active material, and a positive electrode and a lithium secondary battery including the same, and more particularly, to a positive electrode active material having improved high temperature stability by including a coating layer containing a specific concentration of thermally stable titanium dioxide (TiO 2), and a positive electrode and a lithium secondary battery having improved high temperature stability by including the same. Background As technology advances and demand for mobile devices increases, demand for secondary batteries as an energy source has increased significantly. Among these secondary batteries, commercialization of lithium secondary batteries having high energy density, high voltage, long cycle life, and low self-discharge rate is continuously expanding. Lithium cobalt oxide (LiCoO 2), lithium nickel oxide (LiNiO 2), lithium manganese oxide (LiMnO 2 or LiMn 2O4), or lithium iron phosphate compound (LiFePO 4) has been used as a positive electrode active material of a lithium secondary battery. Among them, lithium cobalt oxide has advantages of high operating voltage and excellent capacity characteristics, but it is difficult to realize commercial application in a large-capacity battery due to high price and unstable supply of cobalt as a raw material. Since the structural stability of lithium nickel oxide is poor, it is difficult to achieve sufficient life characteristics. Lithium manganese oxide has excellent stability but has a problem of poor capacity characteristics. Accordingly, lithium composite transition metal oxides containing two or more transition metals have been developed to compensate for the problem of lithium transition metal oxides containing only nickel (Ni), cobalt (Co), or manganese (Mn), wherein lithium nickel cobalt manganese oxides containing Ni, co, and Mn have been widely used in the field of electric vehicle batteries. Conventional lithium nickel cobalt manganese oxides are typically in the form of spherical secondary particles with tens or hundreds of primary particles aggregated. However, with the lithium nickel cobalt manganese oxide in the form of secondary particles in which many primary particles are aggregated as described above, there are problems in that particle breakage in which the primary particles fall off during rolling in the preparation of the positive electrode and cracking occurs in the particles during charge and discharge. In the case where particle breakage or cracking occurs in the positive electrode active material, there is a problem in that deterioration of the active material is aggravated. In particular, with the demand for lithium secondary batteries with high energy density, the nickel content in the positive electrode active material tends to gradually increase. However, with the positive electrode active material having a high nickel content, since a large amount of highly reactive Ni +4 ions are generated if charge and discharge are repeated, structural collapse of the positive electrode active material occurs, and as a result, there is a problem in that the degradation rate of the positive electrode active material increases, thereby deteriorating the life characteristics and reducing the safety of the battery. Therefore, there is a need to develop a positive electrode active material that can achieve both high capacity and high thermal stability. Disclosure of Invention Technical problem An aspect of the present invention provides a positive electrode active material having excellent thermal stability. Another aspect of the present invention provides a positive electrode including the positive electrode active material and a lithium secondary battery having excellent thermal stability by including the positive electrode. Technical proposal [1] The present invention provides a positive electrode active material comprising a lithium nickel-based oxide having a nickel content of 70 mol% or more in all metal elements except lithium, a first coating layer formed on the lithium nickel-based oxide, and a second coating layer formed on the first coating layer, Wherein the first coating layer contains a coating element M1 (M1 is at least one selected from the group consisting of nickel (Ni), cobalt (Co) and aluminum (Al)), The second coating comprises a coating element M2 (M2 is titanium (Ti)), The content of titanium contained in the second coating layer measured by X-ray photoelectron spectroscopy (XPS) is 0.7 to 3.3 at% based on the total content of Ni, co, lithium (