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KR-20260062898-A - POSITIVE ELECTRODE MATERIAL, POSITIVE ELECTRODE AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

KR20260062898AKR 20260062898 AKR20260062898 AKR 20260062898AKR-20260062898-A

Abstract

The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery, wherein the cathode material comprises secondary particles formed by the aggregation of a plurality of primary particles, wherein the plurality of primary particles have an average particle size measured from an SEM image of 1.5 μm or more and 5.0 μm or less, the particle size of the primary particles is a particle size based on the major axis of the primary particles, and a first cathode active material having a degree of single crystallization calculated from Formula 1 described in this specification of 1.0 μm³ or more and 4.0 μm³ or less; A second positive active material comprising a plurality of primary particles aggregated into secondary particles, wherein the plurality of primary particles have an average particle size of less than 1.0 μm as measured from an SEM image, the particle size of the primary particles is a particle size based on the major axis of the primary particles, and the degree of single crystallization calculated from Equation 1 described in the present specification is 1.0 μm or less ; wherein the first positive active material satisfies the condition that the average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer is larger than that of the second positive active material, thereby improving the energy density, charge/discharge capacity, and efficiency characteristics of the electrode and battery including the same.

Inventors

  • 신예원
  • 이준우
  • 정진후
  • 류현모
  • 송세연
  • 김종혁
  • 송지우

Assignees

  • 주식회사 엘지화학

Dates

Publication Date
20260507
Application Date
20251029
Priority Date
20241029

Claims (17)

  1. A first positive active material comprising secondary particles aggregated from a plurality of primary particles, wherein the plurality of primary particles have an average particle size measured from an SEM image of 1.5 μm or more and 5.0 μm or less, the particle size of the primary particles is the particle size based on the major axis of the primary particles, and the degree of single crystallization calculated from the following Formula 1 is 1.0 μm³ or more and 4.0 μm³ or less; and A second positive active material comprising a plurality of primary particles aggregated into secondary particles, wherein the plurality of primary particles have an average particle size of less than 1.0 μm as measured from an SEM image, the particle size of the primary particles is the particle size based on the major axis of the primary particles, and the degree of single crystallization calculated from the following Equation 1 is 1.0 μm 3 or less; The above-mentioned first positive active material is a positive material having a larger average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer than the above-mentioned second positive active material: [Equation 1] In the above Equation 1, radius(grain) is the radius of the grain cross-section assuming the grain cross-section is circular, for grain cross-sections with a cross-sectional area of 0.1 μm² or more among all grain cross-sections identifiable from the cross-section of a particle having a size within the range of the average particle diameter (D 50 ), as observed from the backscattered electron diffraction (EBSD) pattern on the SEM image of the particle cross-section (measured under conditions of acceleration voltage 20 kV, WD 15 mm, measurement magnification 3,000x (width 25 μm * height 25 μm), step size 0.04 μm). n is the number of grains.
  2. In claim 1, The plurality of primary particles of the first positive active material include disk-type primary particles, and The above-mentioned disc-shaped primary particle is a cathode material in which, regarding the primary particle observed from an SEM image of the surface or cross-section of the secondary particle, when a virtual tangent line having the most contact points is drawn for each of the two boundary lines of the primary particle existing within an angle of 45° or less with respect to the major axis direction, and a virtual line crossing the two tangent lines is drawn, the internal angle on the same side is 150° or more and 210° or less, the minor diameter is 0.3 μm or more, and the aspect ratio (major axis/minor diameter) is 1.5 or more.
  3. In claim 2, The above plurality of primary particles comprises three or more disk-type primary particles, forming an anode material.
  4. In claim 2, The above-mentioned disk-shaped primary particle is an anode material having a short diameter of 0.7 μm or more.
  5. In claim 1, The first positive active material is a positive material having a single crystallinity calculated from Formula 1 of 1.0 μm³ or more and 2.5 μm³ or less.
  6. In claim 1, The above-mentioned first positive active material is a positive material comprising 10% or more and 90% or less by weight relative to the total weight of the first positive active material and the second positive active material.
  7. In claim 1, The above-mentioned first positive active material is a positive material comprising a first lithium transition metal composite oxide containing 60 mol% or more of nickel among the total transition metals.
  8. In claim 7, The above-mentioned first lithium transition metal composite oxide is a cathode material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li x1 Ni a1 Co b1 Mn c1 M 1 d1 O 2 In the above chemical formula 1, M1 is one or more 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, and 0.9≤x1≤1.3, 0.6≤a1<1.0, 0<b1<0.4, 0<c1<0.4, 0≤d1≤0.2, a1+b1+c1+d1=1.
  9. In claim 1, A cathode material in which the plurality of primary particles of the first cathode active material include single-crystal primary particles.
  10. In claim 1, The first positive active material is a positive material having an average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer of 7.0 μm or more and 20.0 μm or less.
  11. In claim 1, The second positive active material is a positive material having a single crystallinity calculated from Formula 1 of 0.03 μm³ or more and 0.80 μm³ or less.
  12. In claim 1, The above-mentioned second positive active material is a positive material comprising a second lithium transition metal composite oxide containing 60 mol% or more of nickel among the total transition metals.
  13. In claim 12, The above-mentioned second lithium transition metal composite oxide is a cathode material having a composition represented by the following chemical formula 2: [Chemical Formula 2] Li x2 Ni a2 Co b2 Mn c2 M 2 d2 O 2 In the above chemical formula 2, M 2 is one or more 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, and 0.9≤x2≤1.3, 0.6≤a2<1.0, 0<b2<0.4, 0<c2<0.4, 0≤d2≤0.2, a2+b2+c2+d2=1.
  14. In claim 1, The above second positive active material is a positive material having an average particle size (D 50 ) according to the volume cumulative distribution measured using a laser diffraction particle size analyzer of 2.0 μm or more and 6.0 μm or less.
  15. In claim 1, The above cathode material is a cathode material having a single crystallinity calculated from Equation 1 of 0.05 μm³ or more and 3.0 μm³ or less.
  16. A cathode comprising a cathode material according to any one of claims 1 to 15.
  17. A lithium secondary battery comprising a positive electrode according to claim 16; a negative electrode; a separator interposed between the positive electrode and the negative electrode and an electrolyte.

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 recent technological advancements in electric vehicles and the like, the demand for high-capacity secondary batteries is increasing, and accordingly, research on high-nickel (High Ni) cathode active materials with excellent capacity characteristics is actively underway. High-nickel cathode active materials formed with a secondary particle structure in which primary particles are aggregated undergo structural degradation during the charging and discharging of lithium secondary batteries, but also experience relatively significant changes in lattice structure constants, that is, changes in volume within the unit cell. These volume changes cause cracks within the cathode active material. Additionally, cracks may also occur within the cathode active material due to pressure during electrode rolling. The cracks generated in this way within the high-nickel cathode active material become more severe during the charging and discharging process of the lithium secondary battery. Consequently, they act as voids that prevent the electrolyte from reaching or reduce conductivity, thereby degrading the lifespan characteristics of the lithium secondary battery or acting as a factor in increasing resistance. Attempts are being made to manufacture single-particle cathode active materials as a means to minimize crack formation in such secondary particle structures. However, such single-particle cathode active materials have a problem in that the particle size distribution of the single-particle cathode active material obtained after grinding is large due to the non-uniform particle sizes. In addition, single-particle cathode active materials have a low specific surface area, which makes them vulnerable to cell resistance characteristics. Therefore, there is a need for the development of a positive electrode active material that can simultaneously solve the problems of conventional secondary particles and single particles. Meanwhile, Korean Registered Patent Publication No. 10-1785262 (Patent Document 1) discloses large-diameter secondary particles comprising primary particles aggregated into secondary particles, wherein the secondary particles comprise 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. By including primary particles with an average particle size at the micron level, these large-diameter secondary particles can improve rolling density to minimize cracks caused by rolling, etc., and improve cell characteristics by improving the specific surface area through the secondary particle structure. In order to manufacture a cathode active material in the form of secondary particles with a primary particle size at the micron level, as disclosed in Patent Document 1, it is necessary to perform heat treatment at a higher temperature than that for secondary particles with a primary particle size of less than 1 μm at the submicron level. However, as the heat treatment temperature increases, the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure, which causes a decrease in crystallinity and, consequently, a decrease in the performance of the cathode active material. In particular, since nickel is most susceptible to the degeneration of the layered structure of the lithium transition metal composite oxide into a rock salt structure at high heat treatment temperatures, the degeneration becomes more severe when the nickel content in the lithium transition metal composite oxide constituting the cathode active material increases. Therefore, conventionally, as a cathode active material in the form of secondary particles with a primary particle size at the micron level, it could only be applied to a Mid Ni cathode active material in which the nickel content among the transition metals of the lithium transition metal composite oxide is at the 50 mol% level, as in Patent Document 1, and it was not possible to manufacture a cathode active material in the form of secondary particles with a primary particle size at the micron level for a High Ni cathode active material in which the nickel content among the transition metals of the lithium transition metal composite oxide is high and has excellent capacity characteristics. Accordingly, the inventors of the present invention have developed a positive electrode active material (single particle cluster) that can simultaneously solve the problems of conventional secondary particles and single particles in a high nickel (High Ni) positive electrode active material. Additionally, the inventors of the present invention confirmed that when the above single particle cluster is used as a cathode