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KR-20260066981-A - CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, MANUFACTURING METHOD OF THE SAME AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

KR20260066981AKR 20260066981 AKR20260066981 AKR 20260066981AKR-20260066981-A

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery having a lithium and manganese excess composition and comprising: a lithium metal oxide in the form of secondary particles formed by the aggregation of a plurality of primary particles; and a coating layer containing B and Al that covers the entire surface of the secondary particles in the form of a film, wherein the coating layer comprises a first coating layer containing B and a second coating layer containing Al, wherein the first coating layer and the second coating layer have a structure in which they are sequentially and alternately stacked, and the average thickness ratio of the first coating layer and the second coating layer is 1:1.5 to 1:4.5 (first coating layer: second coating layer).

Inventors

  • 남상철
  • 유병용
  • 송준혁

Assignees

  • 포스코홀딩스 주식회사

Dates

Publication Date
20260512
Application Date
20241105

Claims (20)

  1. A lithium metal oxide in the form of secondary particles formed by the aggregation of a plurality of primary particles, having an excess composition of lithium and manganese; and It covers the entire surface of the above secondary particle in the form of a film and includes a coating layer containing B and Al, The above coating layer comprises a first coating layer containing B and a second coating layer containing Al, and the first coating layer and the second coating layer have a structure in which they are sequentially and alternately stacked. A positive electrode active material for a lithium secondary battery, wherein the average thickness ratio of the first coating layer and the second coating layer is 1:1.5 to 1:4.5 (first coating layer: second coating layer).
  2. In paragraph 1, A positive electrode active material for a lithium secondary battery, further comprising a third coating layer containing Al or B, which encases the surface of at least some of the plurality of primary particles present inside the secondary particles in the form of a film.
  3. In paragraph 2, The above third coating layer is a positive electrode active material for a lithium secondary battery that exists in a region within a distance of (3/4)R from the center of the secondary particle, where R is the distance from the center of the secondary particle to the surface.
  4. In paragraph 2, The above third coating layer is a positive electrode active material for a lithium secondary battery that is also present in an area within a distance of 1 μm from the center of the secondary particle.
  5. In paragraph 1, The above coating layer (the entire first coating layer and the second coating layer) is a positive electrode active material for a lithium secondary battery having an average thickness of 0.7 to 2.8 nm.
  6. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the molar ratio of Al to B (Al/B) in the positive electrode active material is 0.8 to 3.0.
  7. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of B in the above positive electrode active material is 0.006 to 0.024 mol% based on the total molar amount of lithium metal oxide.
  8. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of Al in the above positive electrode active material is 0.01 to 0.042 mol% based on the total molar amount of lithium metal oxide.
  9. In paragraph 1, The first coating layer comprises a B-containing compound, and the B-containing compound comprises B₂O₃ as a main component , forming a positive electrode active material for a lithium secondary battery.
  10. In paragraph 1, The above second coating layer comprises an Al-containing compound, and the Al-containing compound comprises Al₂O₃ as a main component , forming a positive electrode active material for a lithium secondary battery.
  11. In Paragraph 9, The above B₂O₃ is an amorphous positive electrode active material for a lithium secondary battery.
  12. In Paragraph 10, The above Al₂O₃ is an amorphous positive electrode active material for a lithium secondary battery.
  13. In paragraph 1, A positive electrode active material for a lithium secondary battery having an average porosity of 10 to 20% of the lithium metal oxide.
  14. In paragraph 1, A positive electrode active material for a lithium secondary battery having a BET specific surface area of 2.5 to 3.5 m² /g.
  15. In paragraph 1, A positive electrode active material for a lithium secondary battery having a tap density of 1.6 to 2.2 g/cc.
  16. In paragraph 1, The above primary particles are positive electrode active materials for lithium secondary batteries having an average aspect ratio of 2.4 to 3.5.
  17. In paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li 1+a (Ni x Co y Mn z M w ) 1-a O 2 In the above chemical formula 1, 0.1≤a≤0.3, 0.2≤x≤0.4, 0≤y≤0.2, 0.5≤z≤0.75, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.
  18. A step of preparing a lithium metal oxide having an excess composition of lithium and manganese in the form of secondary particles formed by the aggregation of multiple primary particles; A step of forming a first coating layer in the form of a film containing B on the lithium metal oxide using an atomic layer deposition (ALD) method; and The method includes the step of forming a second coating layer in the form of an Al-containing film on the lithium metal oxide using an atomic layer deposition method. The step of forming the first coating layer and the step of forming the second coating layer are performed sequentially and alternately. A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the ratio of the number of atomic layer deposition cycles in the step of forming the first coating layer and the number of atomic layer deposition cycles in the step of forming the second coating layer is 1:0.7 to 1:1.23 (first coating layer: second coating layer).
  19. In Paragraph 18, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in the step of forming a first coating layer or a second coating layer, a third coating layer containing Al or B is formed by wrapping the surface of at least some of the plurality of primary particles present inside the secondary particles in the form of a film.
  20. In Paragraph 18, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the average porosity of the prepared lithium metal oxide is 10 to 20%.

Description

Cathode active material for lithium secondary battery, manufacturing method of the same, and lithium secondary battery comprising the same The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. As the application range of lithium-ion batteries expands from small electronic devices to electric vehicles and power storage devices, there is a growing demand for cathode materials with excellent high energy density and high power characteristics. In this regard, lithium and manganese-excess layered lithium metal oxides are attracting attention as next-generation cathode active material candidates due to their very high capacity, such as a charge capacity of 300 mAh/g and a discharge capacity of 250 mAh/g or more, and research on this is currently being actively conducted worldwide. However, since lithium and manganese-excess lithium metal oxides utilize oxygen oxidation-reduction reactions in addition to transition metals, oxygen on the surface or within the bulk is prone to evolving into oxygen gas. Consequently, dense, non-reactive, or low-reactivity spinel/rock salt structures can easily form within the particles, leading to increased structural instability. This structural instability poses a problem that causes overall degradation of lifespan characteristics as cycles progress, including reduced capacity retention, voltage decay, increased resistance growth, and gas evolution. To address this, technology development involving coating lithium and manganese-excess lithium metal oxides is underway; however, while this improves lifespan characteristics, it has limitations in that capacity characteristics are degraded due to reduced lithium ion mobility. Figure 1 is a Bright Field Scanning Transmission Electron Microscopy (BF-STEM) image of a secondary particle cross-section after Focused Ion Beam (FIB) milling of the positive electrode active material prepared according to Example 1. Figure 2 is an Energy Dispersive Spectroscopy (EDS) element mapping image of the Al element in the upper marked area of the image in Figure 1. Figure 3 is an Energy Dispersive Spectroscopy (EDS) elemental mapping image of the Al element in the lower marked area of the image in Figure 1. Figure 4 is an Energy Dispersive Spectroscopy (EDS) element mapping image for element B in the upper display area of the image in Figure 1. Figure 5 is an Energy Dispersive Spectroscopy (EDS) element mapping image for element B in the lower marked area of the image in Figure 1. Figure 6 is a TEM (transmission electron microscope) image of primary particles inside the positive electrode active material according to Experimental Example 2. Terms such as first, second, and third are used to describe various parts, components, regions, layers, and/or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention. The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and/or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and/or components. When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between. Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined. Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %. In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components. Hereinafter, embodiments of the present invention are described in