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EP-4737395-A1 - METHOD FOR PREPARING POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, AND LITHIUM SECONDARY BATTERY COMPRISING POSITIVE ELECTRODE ACTIVE MATERIAL PREPARED USING SAME

EP4737395A1EP 4737395 A1EP4737395 A1EP 4737395A1EP-4737395-A1

Abstract

The present embodiments relate to a method for manufacturing a positive electrode active material for a lithium secondary battery and to a lithium secondary battery comprising the same. In one embodiment, a method for manufacturing a positive electrode active material for a lithium secondary battery comprises: preparing a metal hydroxide comprising nickel, cobalt, and manganese; mixing the metal hydroxide, a lithium raw material, and a dopant raw material to prepare a mixture; preliminarily calcining the mixture to obtain a preliminarily calcined product; subjecting the preliminarily calcined product to a three-step calcination process including a first calcination, a second calcination, and a third calcination to obtain a calcined product in a single-particle form; and mixing the calcined product with a coating raw material and heat-treating the mixture to obtain a metal oxide having a coating layer formed thereon, wherein, in the step of obtaining the calcined product, the second calcination may be performed at a temperature higher than that of the first calcination, and the third calcination may be performed at a temperature lower than that of the first calcination.

Inventors

  • LEE, SUBIN
  • MYUNG, Minhoon
  • SIM, Sung Keun
  • LEE, SEUNGWON
  • CHOI, KWONYOUNG

Assignees

  • Posco Future M Co., Ltd.

Dates

Publication Date
20260506
Application Date
20240626

Claims (19)

  1. A method for manufacturing a positive electrode active material for a lithium secondary battery, the method comprising: preparing a metal hydroxide comprising nickel, cobalt, and manganese; mixing the metal hydroxide, a lithium raw material, and a dopant raw material to prepare a mixture; preliminarily calcining the mixture to obtain a preliminarily calcined product; subjecting the preliminarily calcined product to a three-step calcination process including a first calcination, a second calcination, and a third calcination to obtain a calcined product in a single-particle form; and mixing the calcined product with a coating raw material and heat-treating the mixture to obtain a metal oxide having a coating layer formed thereon, wherein, in the step of obtaining the calcined product, the second calcination is performed at a temperature higher than that of the first calcination, and the third calcination is performed at a temperature lower than that of the first calcination.
  2. The method of claim 1, wherein the first calcination is performed at a temperature of 870°C to 930°C for 2 hours to 6 hours.
  3. The method of claim 1, wherein the second calcination is performed at a temperature of 890°C to 960°C for 0.5 hours to 2 hours.
  4. The method of claim 1, wherein the third calcination is performed at a temperature of 750°C to 870°C for 5 hours to 14 hours.
  5. The method of claim 1, wherein the preliminary calcination is performed at a temperature of 650°C to 770°C for 3 hours to 10 hours.
  6. The method of claim 1, wherein, in the step of preparing the mixture, the dopant raw material comprises an aluminum raw material, a yttrium raw material, and a zirconium raw material.
  7. The method of claim 6, wherein the aluminum raw material is mixed in an amount of 500 ppm to 1,500 ppm based on the total weight of the metal hydroxide.
  8. The method of claim 6, wherein the yttrium raw material is mixed in an amount of 400 ppm to 2,000 ppm based on the total weight of the metal hydroxide.
  9. The method of claim 6, wherein the zirconium raw material is mixed in an amount of 1,200 ppm to 2,800 ppm based on the total weight of the metal hydroxide.
  10. The method of claim 1, wherein the coating raw material comprises a cobalt coating raw material and an aluminum coating raw material.
  11. The method of claim 10, wherein the cobalt coating raw material is mixed in an amount of 1.5 mol% to 3 mol% based on 100 g of the calcined product.
  12. The method of claim 10, wherein the aluminum coating raw material is mixed in an amount of 500 ppm to 1,500 ppm based on 100 g of the calcined product.
  13. The method of claim 10, wherein the cobalt coating raw material comprises at least one selected from Co(OH) 2 , CoO, Co 3 O 4 , CoCO 3 , cobalt acetate, and cobalt oxalate.
  14. The method of claim 10, wherein the aluminum coating raw material comprises at least one selected from Al(OH) 3 , Al 2 (SO 4 ) 3 , Al(NO 3 ) 3 , Al 2 O 3 , and AlCl 3 .
  15. The method of claim 1, wherein the heat treatment for obtaining the metal oxide having the coating layer formed thereon is performed at 660°C to 760°C for 3 hours to 8 hours.
  16. The method of claim 1, wherein the metal oxide having the coating layer formed thereon is represented by the following Chemical Formula 1: where 0.8 ≤ a ≤ 1.2, 0.8 ≤ x ≤ 0.99, 0 < y ≤ 0.06, 0 < z ≤ 0.14, 0 < w 1 ≤ 0.05, 0 ≤ w 2 < 0.05, and x + y + z + w 1 + w 2 = 1, wherein M 1 comprises Al, Y, and Zr, and M 2 comprises one or more selected from B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, and Sr.
  17. The method of claim 1, wherein, when the positive electrode active material is subjected to five pressings using a roll press at a press gauge of 0.01 mm, the total amount of fines having a particle diameter of less than 1 µm is 2 vol% or less.
  18. A positive electrode for a lithium secondary battery comprising the positive electrode active material manufactured according to any one of claims 1 to 17.
  19. A lithium secondary battery comprising the positive electrode of claim 18.

Description

[Technical Field] The present embodiments relate to a method for manufacturing a positive electrode active material for a lithium secondary battery, and to a lithium secondary battery comprising a positive electrode active material manufactured by the method. [Background Art] In recent years, driven by the explosive growth in demand for electric vehicles and the increasing requirement for longer driving ranges, development of secondary batteries having high capacity and high energy density has been actively pursued worldwide. In particular, high-nickel NCM positive electrode materials have been employed to meet these demands. However, as the nickel content increases, particle strength decreases, leading to formation of microcracks during charge and discharge. This in turn increases the specific surface area of the positive electrode material, which promotes side reactions with the electrolyte and thereby increases gas generation. Furthermore, due to structural instability, unstable Ni3+ is reduced to stable Ni2+ and converted into stable NiO, thereby increasing the degree of cation mixing. Thus, it is difficult to apply such materials directly as positive electrode active materials for lithium-ion batteries used in electric vehicles or energy storage systems. To address these problems, approaches have been proposed in which a positive electrode material is manufactured in a single-particle form by maximizing the size of primary particles, rather than using secondary particles in which multiple primary particles are agglomerated. However, manufacturing a positive electrode material in a single-particle form typically requires calcination at higher temperatures compared to secondary particles. Under such conditions, under-calcination frequently occurs, resulting in defects in the layered crystal structure and deterioration in electrochemical properties such as capacity and output. Furthermore, when the calcination temperature is lowered to mitigate such defects, the crystallite size within the single particle does not sufficiently grow, which leads to deterioration in particle strength and cycle life characteristics. [Detailed Description of the Invention] [Technical Problem] The present embodiments aim to provide a method for manufacturing a positive electrode active material for a lithium secondary battery that exhibits excellent electrochemical characteristics while improving cycle life and resistance characteristics, as well as to provide a lithium secondary battery comprising the positive electrode active material. [Technical Solution] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment comprises: preparing a metal hydroxide comprising nickel, cobalt, and manganese; mixing the metal hydroxide, a lithium raw material, and a dopant raw material to prepare a mixture; preliminarily calcining the mixture to obtain a preliminarily calcined product; subjecting the preliminarily calcined product to a three-step calcination process including a first calcination, a second calcination, and a third calcination to obtain a calcined product in a single-particle form; and mixing the calcined product with a coating raw material and heat-treating the mixture to obtain a metal oxide having a coating layer formed thereon. In the step of obtaining the calcined product, the second calcination may be performed at a temperature higher than that of the first calcination, and the third calcination may be performed at a temperature lower than that of the first calcination. In another embodiment, a lithium secondary battery may include a positive electrode comprising the positive electrode active material manufactured according to the embodiment described above. [Effects of the Invention] According to the present embodiment, by performing the first, second, and third calcinations in a three-step (STEP) process-wherein the second calcination is carried out at a temperature higher than the first calcination, and the third calcination is carried out at a temperature lower than the first calcination-the crystal structure can be stabilized and the particle strength can be enhanced. Accordingly, the present embodiment makes it possible to realize a positive electrode active material in a single-particle form that nevertheless exhibits excellent electrochemical properties, as well as improved cycle life and resistance characteristics. [Best Mode for Carrying Out the Invention] The terms "first," "second," "third," and the like are used to describe various parts, components, regions, layers, and/or sections, but are not limited thereto. These terms are merely used to distinguish one part, component, region, layer, or section from another. Thus, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention. Technical terms used herein