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EP-4738458-A1 - CATHODE ACTIVE MATERIAL, METHOD FOR PREPARING SAME, CATHODE COMPRISING SAME, AND ALL-SOLID STATE BATTERY

EP4738458A1EP 4738458 A1EP4738458 A1EP 4738458A1EP-4738458-A1

Abstract

A cathode active material, according to one embodiment of the present invention, comprises: a core including a lithium-transition metal composite oxide; a first coating layer formed on the surface of the core; and a second coating layer formed on the surface of the first coating layer, wherein the first coating layer includes a lithium-transition metal composite oxide having a structure that is different from the lithium-transition metal composite oxide included in the core, and the second coating layer includes a sulfur compound.

Inventors

  • YOON, JI-YOUNG

Assignees

  • SK On Co., Ltd.

Dates

Publication Date
20260506
Application Date
20240528

Claims (20)

  1. A cathode active material comprising: a core including a lithium-transition metal composite oxide; and a first coating layer formed on a surface of the core; and a second coating layer formed on a surface of the first coating layer, wherein the first coating layer includes a lithium-transition metal composite oxide having a different structure from the lithium-transition metal composite oxide included in the core, and the second coating layer includes a sulfur compound.
  2. The cathode active material of claim 1, wherein the core includes the lithium-transition metal composite oxide having a layered structure.
  3. The cathode active material of claim 1, wherein the core includes the lithium-transition metal composite oxide according to the following Chemical Formula 1: [Chemical Formula 1] Li a Ni b M c O 2 In Chemical Formula 1, M is at least one element selected from Na, Mg, Ca, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, and Ba, and 0.90<a<1.5, 0.33≤b≤1, 0≤c≤0.7.
  4. The cathode active material of claim 1, wherein the first coating layer includes the lithium-transition metal composite oxide having a spinel structure.
  5. The cathode active material of claim 4, wherein the first coating layer further includes at least one of the lithium-transition metal composite oxide having a rock salt structure or the lithium-transition metal composite oxide having a layered structure.
  6. The cathode active material of claim 1, wherein the first coating layer includes the lithium-transition metal composite oxide according to the following Chemical Formula 2: [Chemical Formula 2] Li x M y O z In Chemical Formula 2, M is at least one element selected from Ni, Co, Mn, Na, Mg, Ca, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, and Ba, and 0≤x≤4, 0≤y≤4, and 0≤z≤8.
  7. The cathode active material of claim 1, wherein a thickness of the first coating layer is 0.1 to 500 nm.
  8. The cathode active material of claim 1, wherein a cation mixing ratio is 7% or less.
  9. The cathode active material of claim 1, wherein the sulfur compound includes at least one compound according to the following Chemical Formula 3: [Chemical Formula 3] Li x M y S z O f In Chemical Formula 3, M is selected from an alkali metal, an alkaline earth metal, a transition metal, a Group 13 element, a Group 14 element, a rare earth element, a substituted or unsubstituted aliphatic hydrocarbon group, and combinations thereof, and 0≤x≤10, 0≤y≤10, 0<z≤10, and 0≤f≤24.
  10. The cathode active material of claim 1, wherein the sulfur compound includes sulfur oxide, and the sulfur oxide is present in an amount of 200 to 8,000 ppm, based on a total weight of the second coating layer.
  11. The cathode active material of claim 1, wherein the second coating layer further includes at least one element selected from P, B, Si, Al, and W.
  12. A method for preparing a cathode active material, comprising the cathode active material of any one of claims 1 to 11.
  13. The method of claim 12, including: a base material preparation operation of forming a core by a dry heat treatment process for a mixture of a precursor including a transition metal raw material and a lithium raw material; and a base material pretreatment operation of forming a precursor coating layer on a surface of the core.
  14. The method of claim 13, further including a coating layer formation operation of forming a first coating layer and a second coating layer, wherein a first coating layer is formed by a heat treatment process for a core in the coating layer formation operation.
  15. The method of claim 14, wherein, in the coating layer formation operation, the second coating layer is formed of a complex sulfate compound according to the following Chemical Formula 4: In the Chemical Formula 4, X is selected from an alkali metal, an alkaline earth metal, a transition metal, a Group 13 element, a Group 14 element, a Group 16 element, a rare earth element, a substituted or unsubstituted aliphatic hydrocarbon group, and a combination thereof, and 1≤a≤5 and 1≤b≤5.
  16. The method of claim 14, wherein, in the coating layer formation operation, the heat treatment process is performed in air at a temperature of 300°C or less and for a time of 20 hours or less.
  17. A cathode comprising the cathode active material of any one of claims 1 to 11.
  18. An all-solid-state battery comprising the cathode of claim 17.
  19. The all-solid-state battery of claim 18, further including a sulfide-based solid electrolyte.
  20. The all-solid-state battery of claim 19, wherein the sulfide-based solid electrolyte is an argyrodite-based solid electrolyte.

Description

Technical Field The present disclosure relates to a cathode active material, a method for preparing the same, a cathode including the same, and an all-solid-state battery. Background Art Recently, due to environmental issues such as global warming or the like, interest in eco-friendly electric vehicles that may be replaced with fossil fuel-based vehicles has increased. Lithium secondary batteries may be one of the primary energy sources leading existing electric vehicle market due to their high energy density and advanced industrial technology. However, existing lithium secondary batteries utilizing liquid electrolytes such as organic solvents and the like may have issues such as a risk of ignition due to leakage of the electrolyte upon impact, and expansion, explosion, or the like of the batteries due to chemical decomposition and gas generation of the electrolyte. Therefore, in order to solve the problems, an all-solid-state battery to which a solid electrolyte is applied is attracting attention as a next-generation energy source, and research and development thereon are actively underway. Disclosure of Invention Technical Problem An aspect of the present disclosure is to provide a cathode active material capable of improving a lifespan characteristic of a battery. Another aspect of the present disclosure is to provide a cathode active material having high capacity. Another aspect of the present disclosure is to provide a cathode active material having excellent resistance performance. Another aspect of the present disclosure is to provide an all-solid-state battery having excellent electrochemical performance. Another aspect of the present disclosure is to provide an all-solid-state battery having excellent safety. Solution to Problem A cathode active material according to an embodiment includes a core including a lithium-transition metal composite oxide; and a first coating layer formed on a surface of the core; and a second coating layer formed on a surface of the first coating layer, wherein the first coating layer includes a lithium-transition metal composite oxide having a different structure from the lithium-transition metal composite oxide included in the core, and the second coating layer includes a sulfur compound. The core may include the lithium-transition metal composite oxide having a layered structure. The core may include the lithium-transition metal composite oxide according to the following Chemical Formula 1:         [Chemical Formula 1]     LiaNibMcO2 In Chemical Formula 1, M is at least one element selected from Na, Mg, Ca, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, and Ba, and 0.90<a<1.5, 0.33≤b≤1, 0≤c≤0.7. The first coating layer may include the lithium-transition metal composite oxide having a spinel structure. The first coating layer may further include at least one of the lithium-transition metal composite oxide having a rock salt structure or the lithium-transition metal composite oxide having a layered structure. The first coating layer may include the lithium-transition metal composite oxide according to the following Chemical Formula 2:         [Chemical Formula 2]     LixMyOz In Chemical Formula 2, M is at least one element selected from Ni, Co, Mn, Na, Mg, Ca, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, and Ba, and 0≤x≤4, 0≤y≤4, and 0≤z≤8. A thickness of the first coating layer may be 0.1 to 500 nm. The cathode active material may have a cation mixing ratio of 7% or less. The sulfur compound may include at least one compound according to the following Chemical Formula 3:         [Chemical Formula 3]     LixMySzOf In Chemical Formula 3, M is selected from an alkali metal, an alkaline earth metal, a transition metal, a Group 13 element, a Group 14 element, a rare earth element, a substituted or unsubstituted aliphatic hydrocarbon group, and combinations thereof, and 0≤x≤10, 0≤y≤10, 0<z≤10, and 0≤f≤24. The sulfur compound may include sulfur oxide. The sulfur oxide may be present in an amount of 200 to 8,000 ppm, based on a total weight of the second coating layer. The second coating layer may further include at least one element selected from P, B, Si, Al, and W. A method for preparing a cathode active material according to an embodiment prepares the cathode active material according to any one of the embodiments described above. The method may include a base material preparation operation of forming a core by a dry heat treatment process for a mixture of a precursor including a transition metal raw material and a lithium raw material; and a base material pretreatment operation of forming a precursor coating layer on a surface of the core. The method may further include a coating layer formation operation of forming a first coating layer and a second coating layer. In the coating layer formation operation, the first coating layer may be formed by a heat treatment process for the core. In the coating laye