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US-20260128298-A1 - LITHIUM COMPOSITE OXIDE, AND CATHODE ACTIVE MATERIAL FOR SECONDARY BATTERY, COMPRISING SAME

US20260128298A1US 20260128298 A1US20260128298 A1US 20260128298A1US-20260128298-A1

Abstract

A cathode active material of the present invention comprises a lithium nickel-based composite oxide comprising secondary particles formed by the aggregation of primary particles, wherein some cations and some anions in the lithium nickel-based composite oxide are replaced by a cation M′ and a fluoride anion (F − ), respectively, which are contained in a fluorine-based compound, and the average Ni occupancy in the Li 3a site, obtained through Rietveld refinement using X-ray diffraction of the secondary particles, is 1.1-1.5%.

Inventors

  • Kyu Suk Han
  • Jin Hyeok Choi
  • Jae Hoon Shin
  • Seul Gi LEE

Assignees

  • ECOPRO BM CO., LTD.

Dates

Publication Date
20260507
Application Date
20230427
Priority Date
20221031

Claims (13)

  1. 1 . A cathode active material comprising a lithium nickel-based composite oxide including secondary particles formed by aggregation of primary particles, wherein some cations and some anions in the lithium nickel-based composite oxide are replaced by a cation M′ and a fluoride anion (F − ), respectively, included in a fluorine-based compound, and wherein average Ni occupancy in a Li 3a site obtained from a Rietveld refinement using X-ray diffraction (XRD) of the secondary particles is from 1.1% to 1.5%.
  2. 2 . The cathode active material of claim 1 , wherein an average c-axis length obtained from the Rietveld refinement using X-ray diffraction of the secondary particles is from 14.184 Å to 14.186 Å.
  3. 3 . The cathode active material of claim 1 , wherein, in an XRD analysis for the lithium nickel-based composite oxide, FWHM corrected (104) corrected by the following Relation Formula 1 is from 0.160 to 0.19° (2θ): [ Relation ⁢ Formula ⁢ 1 ]   FWHM corrected ⁢ ( 104 ) = FWHM measured ⁢ ( 104 ) - FWHM SI ⁢ powder ⁢ ( 220 ) wherein in Relation Formula 1, FWHM measured (104) means a full width at half maximum of (104) peak observed at 44.5±1.0° (2θ) in the XRD analysis of the lithium nickel-based composite oxide, and FWHM Si (220) means a full width at half maximum of (220) peak observed around 47.3±1.00 (2θ) in the XRD measurement value of Si powder.
  4. 4 . The cathode active material of claim 1 , wherein each secondary particle includes a surface portion and an inside portion, and an average primary particle size of the surface portion of the secondary particle is larger than an average primary particle size of the inside portion of the secondary particle.
  5. 5 . The cathode active material of claim 4 , wherein primary particles having a size of 200 nm or greater and less than 500 nm account for 50% by volume to 100% by volume of the primary particles forming the secondary particle in the inside portion of the secondary particle.
  6. 6 . The cathode active material of claim 4 , wherein primary particles having a size of 500 nm to 10.0 m account for 50% by volume to 100% by volume of the primary particles forming the secondary particle in the surface portion of the secondary particle.
  7. 7 . The cathode active material of claim 4 , wherein an average aspect ratio of primary particles of the surface portion of the secondary particle is larger than an average aspect ratio of the primary particles of the inside portion of the secondary particle.
  8. 8 . The cathode active material of claim 4 , wherein 50% or more of primary particles of the surface portion of the secondary particle are formed such that a major axis direction of each primary particle has an angle of less than ±30° from a line connecting the surface and a center of the secondary particle.
  9. 9 . The cathode active material of claim 4 , wherein 50% or more of primary particles of the surface portion of the secondary particle are formed such that a lithium ion diffusion path formed in the primary particles has an angle of less than ±30° from a line connecting the surface and a center of the secondary particle.
  10. 10 . The cathode active material of claim 4 , wherein the secondary particle exhibits greatest peak intensity at 684.3 eV to 685.0 eV as a result of analyzing is binding energy of fluorine obtained through XPS (X-ray photoelectron spectrometer) measurement.
  11. 11 . The cathode active material of claim 1 , further comprising a coating oxide occupying at least a portion of at least any one or more of surfaces of the secondary particles, grain boundaries between the primary particles, or surfaces of the primary particles.
  12. 12 . A cathode comprising the cathode active material of claim 1 .
  13. 13 . A secondary battery comprising the cathode of claim 12 .

Description

TECHNICAL FIELD The present disclosure relates to a lithium nickel-based composite oxide and a cathode active material for a secondary battery including the same, and relates to a cathode active material in which cation and anion sites in a crystal structure in a polycrystal-type lithium nickel-based composite oxide are simultaneously replaced by a fluorine-based compound. BACKGROUND ART With the advancement of portable mobile electronic devices such as smartphones, MP3 players and tablet PCs, the demand for secondary batteries capable of storing electrical energy is explosively increasing. In particular, with the advent of electric vehicles, medium- to large-sized energy storage systems and portable devices requiring high energy density, the demand for lithium secondary batteries is increasing. As a lithium composite oxide included in a cathode active material, a material that has received the most attention recently is lithium nickel manganese cobalt oxide (Li(NixCoyMnz)O2, herein, x, y, z are atomic fractions of each independent oxide composition element, and 0<x≤1, 0<y≤1, 0<z≤1 and 0<x+y+z≤1). This cathode active material has an advantage of producing higher capacity compared to LiCoO2 that has been actively studied and used as a cathode active material, and has an advantage of low price since the Co content is relatively small. However, such a lithium composite oxide accompanies a volume change due to intercalation and deintercalation of lithium ions during charge and discharge. There is a problem in that primary particles of the lithium composite oxide rapidly change in volume during charge and discharge, cracks occur within secondary particles due to repeated charge and discharge, or collapse of a crystal structure or phase transition in a crystal structure occurs. In order to compensate for such disadvantages, demand for a nickel (Ni) rich system-hi nickel system having a Ni content of 60% or greater as a cathode active material of a secondary battery began to increase. However, whereas such an active material with a nickel rich system has an excellent advantage of exhibiting high capacity, there are problems of increasing structural instability due to Li/Ni cation mixing caused by an increase in the Ni content, and rapidly deteriorating lifetime properties at room temperature and high temperature due to physical disconnection of inner particles caused by microcracks, deepening of electrolyte depletion and the like. DISCLOSURE Technical Problem The present disclosure is directed to providing a cathode active material in which a cation and an anion in a lithium nickel-based composite oxide are simultaneously replaced by a cation M′ and a fluoride anion (F−), respectively, included in a fluorine-based compound, thereby having controlled Ni occupancy in a Li 3a site. In addition, the present disclosure is directed to providing a cathode active material exhibiting both an effect of cation mixing suppression and an effect of structure strengthening by fluorine that replaces oxygen. In addition, the present disclosure is directed to providing a cathode active material having significantly reduced lattice defects and residual lithium occurring during a high-temperature reaction. In addition, the present disclosure is directed to providing a cathode active material improving a battery lifetime, and significantly suppressing gas generation during high-temperature storage. In addition, the present disclosure is directed to providing a cathode active material significantly improving battery properties such as capacity/efficiency and c-rate of a battery Technical Solution A cathode active material of one embodiment of the present disclosure includes a lithium nickel-based composite oxide including secondary particles formed by aggregation of primary particles, wherein some cations and some anions in the lithium nickel-based composite oxide are replaced by a cation M′ and a fluoride anion (F−), respectively, included in a fluorine-based compound, and average Ni occupancy in a Li 3a site obtained from a Rietveld refinement using X-ray diffraction of the secondary particles is from 1.1% to 1.5%. In one embodiment, an average c-axis length obtained from the Rietveld refinement using X-ray diffraction of the secondary particles may be from 14.184 Å to 14.186 Å. In one embodiment, in an XRD analysis for the lithium nickel-based composite oxide, FWHMcorrected (104) corrected by the following Relation Formula 1 may be from 0.16° to 0.19° (2θ). In Relation Formula 1, FWHMmeasured (104) means a full width at half maximum of (104) peak observed at 44.5±1.0° (2θ) in the XRD analysis of the lithium nickel-based composite oxide, and FWHMSi (220) means a full width at half maximum of (220) peak observed around 47.3±1.0° (2θ) in the XRD measurement value of Si powder. In one embodiment, an average aspect ratio of the primary particles of a surface portion of the secondary particle may be larger than an average aspect ratio of