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KR-20260062406-A - POSITIVE ELECTRODE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY-BATTERY COMPRISING THE SAME

KR20260062406AKR 20260062406 AKR20260062406 AKR 20260062406AKR-20260062406-A

Abstract

The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery.

Inventors

  • 한원상
  • 홍유식
  • 신은정
  • 최정빈
  • 이원균
  • 임현주
  • 박진규

Assignees

  • 주식회사 엘지화학

Dates

Publication Date
20260507
Application Date
20241029

Claims (10)

  1. A first positive electrode active material comprising a lithium iron phosphate-based compound; and a second positive electrode active material comprising a lithium complex transition metal oxide; comprising, The molar ratio of the first positive active material and the second positive active material is 3:1 to 5:1, and A cathode material having a skewness of -0.5 or less calculated according to Equation 1 below in the volume-based particle size distribution (PSD) graph of the first cathode active material. [Equation 1] Skewing = [(Mean - Mode) / (Standard Deviation)]
  2. In claim 1, The above-mentioned skewness is -2.0 to -1.0, and the cathode material.
  3. In claim 1, A cathode material having an average particle size (D 50 ) of the first cathode active material of 1㎛ to 5㎛.
  4. In claim 1, A cathode material having a span value of 1 to 2 according to the following Formula 2 of the first cathode active material. [Equation 2] Span = (D 90 - D 10 )/D 50 )
  5. In claim 1, The above-mentioned first positive active material is a positive material comprising a lithium iron phosphate-based compound and a coating layer including carbon (C) formed on the lithium iron phosphate-based compound.
  6. In claim 1, The above lithium iron phosphate-based compound is a cathode material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Fe 1-a M a PO 4 In the above chemical formula 1, M is one or more selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y, and -0.2≤x≤0.2, 0≤a≤0.9.
  7. In claim 1, A cathode material having an average particle size (D 50 ) of the second cathode active material of 3㎛ to 20㎛.
  8. In claim 1, The above lithium composite transition metal oxide is a cathode material having a composition represented by the following chemical formula 2: [Chemical Formula 2] Li 1+y Ni b Co c M1 d M2 e O 2 In the above chemical formula 2, M1 is Mn, Al, or a combination thereof, and M2 is one or more selected from W, Mo, Cr, Zr, Ti, Mg, Ta, B, and Nb, and -0.05≤y≤0.3, 0.6≤b<1.0, 0<c<0.4, 0<d<0.4, 0≤e≤0.1, b+c+d+e=1.
  9. A cathode comprising a cathode material according to any one of claims 1 to 8.
  10. A lithium secondary battery comprising a positive electrode according to claim 9.

Description

Positive ELECTRODE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY-BATTERY COMPRISING THE SAME The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery. With the increasing technological development and demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Lithium secondary batteries consist of four major components: a positive electrode, a negative electrode, a separator, and an electrolyte. Among these, the positive electrode active material, which is included in the positive electrode, plays a significant role in determining the battery's capacity, output, and lifespan. Currently used positive electrode active materials include NCM-based positive electrode active materials containing nickel, cobalt, manganese, and/or aluminum, and LFP (lithium iron phosphate)-based positive electrode active materials. Meanwhile, improving the performance of the positive electrode active material is essential for lithium secondary batteries to have high energy density, output, and lifespan; consequently, much research is currently being conducted to develop high-performance positive electrode active materials. Recently, as the scope of use for lithium-ion batteries has increased, active development is underway for NCM-based cathode active materials with increased nickel content to increase the energy density of the battery, particularly to increase capacity. However, NCM-based cathode active materials with increased nickel content have a problem of reduced thermal stability due to structural instability caused by the high nickel content. On the other hand, LFP-based cathode active materials, which are cathode active materials with an olivine structure, have the advantage of having excellent thermal stability and price competitiveness, although their capacity is lower compared to NCM-based cathode active materials. However, batteries using 100% LFP-based cathode active materials have a disadvantage of low energy density because the operating voltage is lower compared to batteries using NCM-based cathode active materials. Attempts have been made to utilize a mixture of NCM-based and LFP-based cathode active materials to realize the advantages of each material. However, LFP-based cathode active materials have issues with slow electrical conductivity and lithium ion diffusion rates, which act as resistance when mixed with NCM cathode active materials. Accordingly, there is a need to develop cathode materials that can prevent the electrode resistance from increasing even when NCM cathode active materials and LFP-based cathode active materials are mixed and used. Figure 1 shows the PSD graph of the first cathode active material included in the cathode material in Example 1, Comparative Example 1, Comparative Example 4, and Comparative Example 5. Figure 2 shows the PSD graph of the first cathode active material included in the cathode material in Example 2, Comparative Example 1, and Comparative Examples 5 to 7. Figure 3 shows the PSD graph of the first cathode active material included in the cathode material in Example 1, Comparative Example 1, and Comparative Example 4. Hereinafter, the present invention will be described in more detail to aid in understanding the invention. Terms and words used in the description and claims of the present invention shall not be interpreted as being limited to their ordinary or dictionary meanings, and shall be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. In this specification, a single-particle cathode active material refers to a cathode active material composed of 10 or fewer primary particles, as opposed to a spherical secondary particle cathode active material formed by the aggregation of tens to hundreds of primary particles. Specifically, in this specification, the single-particle cathode active material may be a single particle composed of one primary particle, or it may be a secondary particle formed by the aggregation of several primary particles. In this case, 'primary particle' refers to the smallest unit of a particle recognized when observing the cathode active material through a scanning electron microscope, and 'secondary particle' refers to a secondary structure formed by the aggregation of multiple primary particles. In this specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle size (D 50 ) can be measured, for example, using a laser diffraction method. More spe