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EP-4738470-A1 - POLYCRYSTALLINE CATHODE ACTIVE MATERIAL AND LITHIUM SECONDARY BATTERY CONTAINING THE SAME

EP4738470A1EP 4738470 A1EP4738470 A1EP 4738470A1EP-4738470-A1

Abstract

The present disclosure relates to a novel polycrystalline cathode active material, and more specifically, provides a novel polycrystalline cathode active material having an effect of improving lifetime characteristics while securing excellent output and capacity characteristics by determining an optimal size and number of primary particles and a size of secondary particles by utilizing peak intensities of an H2 phase and an H3 phase.

Inventors

  • NAM, YU JIN
  • SEON, Younghoe
  • KIM, SUN HWA
  • HEO, Seungwoo
  • PARK, Sungyoon
  • LEE, JAE MIN
  • KWON, Ohyeon
  • LEE, JAEKYUN
  • KWAK, Hwan Wook
  • JO, MIN SU

Assignees

  • ECOPRO BM CO., LTD.

Dates

Publication Date
20260506
Application Date
20251031

Claims (11)

  1. A polycrystalline cathode active material, comprising: primary particles comprising nickel and having an average particle diameter (D50) in a range of 500 nm to 5 µm; and secondary particles formed by an agglomeration of the primary particles; wherein a portion of the primary particles is exposed on an outer surface of the secondary particles.
  2. The polycrystalline cathode active material of claim 1, wherein an average particle diameter (D50) of the primary particles and the secondary particles is determined by an H2 intensity ratio calculated by the following Formula 1: H 2 intensity ratio = H 2 intensity H 2 intensity + H 3 intensity × 100 (In Formula 1, the H2 intensity and the H3 intensity are the peak intensities of an H2 phase and an H3 phase obtained through X-ray diffraction (XRD) analysis.)
  3. The polycrystalline cathode active material of claim 1, wherein a number of the primary particles forming the secondary particles is determined by an H2 intensity ratio calculated by the following Formula 1: H 2 intensity ratio = H 2 intensity H 2 intensity + H 3 intensity × 100 (In Formula 1, the H2 intensity and the H3 intensity are the peak intensities of an H2 phase and an H3 phase obtained through X-ray diffraction (XRD) analysis.)
  4. The polycrystalline cathode active material of claim 2, wherein, when a nickel content of the primary particles is in a range of 50 mol% to less than 80 mol%, the average particle diameter (D50) of the primary particles and the secondary particles is measured when the H2 intensity ratio is in a range of 5% to 16%.
  5. The polycrystalline cathode active material of claim 3, wherein, when a nickel content of the primary particles is in a range of 50 mol% to less than 80 mol%, the number of the primary particles forming the secondary particles is measured when the H2 intensity ratio is in a range of 5% to 16%.
  6. The polycrystalline cathode active material of claim 2, wherein, when a nickel content of the primary particles is 80 mol% or more, the average particle diameter (D50) of the primary particles and the secondary particles is measured when the H2 intensity ratio is in a range of 10% to 25%.
  7. The polycrystalline cathode active material of claim 3, wherein, when a nickel content of the primary particles is 80 mol% or more, the number of the primary particles forming the secondary particles is measured when the H2 intensity ratio is in a range of 10% to 25%.
  8. The polycrystalline cathode active material of claim 1, wherein an average particle diameter (D50) of the secondary particles is 1.5 to 5.0 times an average particle diameter (D50) of the primary particles.
  9. The polycrystalline cathode active material of claim 1, wherein the secondary particles are formed by an agglomeration of 2 to 5 primary particles.
  10. A cathode slurry composition, comprising the polycrystalline cathode active material of claim 1 to 9, a conductive agent, and a binder.
  11. A lithium secondary battery, comprising a cathode formed by coating a current collector with the cathode slurry composition of claim 10.

Description

TECHNICAL FIELD The present disclosure relates to a polycrystalline cathode active material and a lithium secondary battery comprising the same. More specifically, the present disclosure relates to a novel polycrystalline cathode active material that exhibits lifetime, capacity, and output characteristics different from those of conventional polycrystalline cathode active materials, and to a lithium secondary battery including the same. BACKGROUND A lithium secondary battery is a battery that stores and releases energy by moving lithium ions between electrodes. Owing to its characteristic of being chargeable and dischargeable, it is extensively utilized in various fields, including electronic devices, electric vehicles, and energy storage systems. In particular, lithium ions, being lighter in weight and possessing a higher energy density than other metal ions, play an important role in the development of high-efficiency batteries. Among the important factors that determine the performance of a lithium secondary battery is the cathode active material, which maintains stability during the insertion and extraction of lithium ions, and directly influences the capacity and lifespan of the battery. Depending on the type of cathode active material, the energy density, output, lifetime, and stability of the battery vary greatly. The cathode active material is generally composed of a lithium metal oxide, and representative examples thereof comprise lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel cobalt manganese oxide (NCM), and lithium nickel cobalt aluminum oxide (NCA). Recently, mid-nickel and high-nickel cathode active materials have attracted attention in order to satisfy the high energy density and capacity demanded in electric vehicles and the like. Nickel-based cathode materials are gaining popularity in markets demanding higher-performance batteries, as their energy density and capacity increase with a higher nickel content. Representative materials include high-nickel NCM (nickel, cobalt, manganese) and NCA (nickel, cobalt, aluminum) materials, which contribute to extending the driving range of electric vehicles and enhancing the energy efficiency of batteries. Cathode active materials can be divided into polycrystalline and single-crystal materials according to their crystal structure. A polycrystalline cathode active material is a structure in which a plurality of small crystal particles gather to form a single particle. Polycrystalline structures are relatively easy to manufacture, are less costly, and exhibit excellent performance at specific charge/discharge rates. However, polycrystalline particles are susceptible to inter-particle cracking during charging and discharging processes, and are accompanied by gas generation, which is disadvantageous in terms of long-term lifespan. In particular, there is a great need to solve the expansion and stability problems caused by gas generation in high-nickel polycrystalline cathode materials. A single crystal cathode material is a particle structure composed of a single crystal. The single-crystal structure has the advantage of reduced inter-particle cracking during charging and discharging, enhanced stability, and an extended lifespan. However, single-crystal materials have the disadvantages of being difficult to manufacture, incurring high costs, and exhibiting inferior output characteristics as compared with polycrystalline materials. Additionally, when having the same nickel composition, the capacity tends to be lower than that of a polycrystalline material, which may result in performance degradation. Accordingly, in order to improve the performance of lithium secondary batteries, it is necessary to develop a novel type of cathode active material that addresses the problems arising in nickel-based cathode active materials and compensates for the shortcomings of polycrystalline and single-crystal cathode active materials. PRIOR ART DOCUMENTS PATENT DOCUMENTS (Patent Document 1) Korean Patent Publication No. 10-2023-0162830 SUMMARY TECHNICAL PROBLEM An object of the present disclosure is to provide a novel polycrystalline cathode active material which, through primary particles having an average particle diameter of 500 nm or greater, is capable of securing excellent output and capacity characteristics while improving lifetime characteristics. Another object of the present disclosure is to provide a lithium secondary battery comprising the polycrystalline cathode active material. SOLUTION TO THE PROBLEM An embodiment of the present disclosure provides a polycrystalline cathode active material comprising primary particles having an average particle diameter (D50) of 500 nm to 5 µm, and secondary particles formed by agglomeration of the primary particles, wherein a portion of the primary particles is exposed on an outer surface of the secondary particles. The average particle diameter (D50) of the primary particles and secondary parti