Positive electrode active material for lithium rechargeable battery, method of producing the same, and lithium rechargeable battery including the same
A surface of a LiCoO 2 -based positive electrode active material to have a rock salt crystal structure is provided. Specifically, a positive electrode active material for a lithium rechargeable battery is provided, including: a core particle containing lithium cobalt oxide doped with aluminum (Al); and a coating layer positioned on a surface of the core particle and containing a cobalt(Co)-based compound having a rock salt crystal structure. A method of producing the positive electrode active material is also provided using a solid-phase method. The positive electrode active material can be applied to a positive electrode, lithium rechargeable battery, battery module, battery pack, and the like.
1. A positive electrode active material for a lithium rechargeable battery, comprising:
a core particle comprising a first region and a second region, wherein the first region and the second region comprise lithium cobalt oxide doped with aluminum (Al); and
a coating layer on a surface of the core particle, wherein the coating layer comprises a cobalt-based compound having a rock salt crystal structure,
wherein a crystal structure of the lithium cobalt oxide doped with Al in the first region is a layered structure, wherein the first region is represented by the following Formula 1:
Li a Co (1-x-y-z) Al x M1 y M2 z O 2 [Formula 1]
wherein M1 and M2 are each independently one selected from the group consisting of Ti, Mg, Zr, Ba, Ca, Ta, Nb, and Mo,
wherein a, x, y, and z are values satisfying 0.95≤a≤1.05, 0<x≤0.02, 0≤y≤0.02, and 0≤z≤0.02, respectively,
wherein a crystal structure of the lithium cobalt oxide doped with Al in the second region is a spinel structure, wherein the second region is represented by the following Formula 2:
Li a-m Co (1-x-y-z) Al x M1 y M2 z O 2
wherein M1 and M2 are each independently one selected from the group consisting of Ti, Mg, Zr, Ba, Ca, Ta, Nb, and Mo, and
wherein a, x, y, z, and m are values satisfying 0.95≤a≤1.05, 0<x≤0.02, 0≤y≤0.02, 0≤z≤0.02, and 0<m<0.75, respectively.
2. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
the cobalt-based compound having a rock salt crystal structure is cobalt(II) oxide.
3. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
the coating layer further comprises cobalt, lithium cobalt oxide, or a combination thereof.
4. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
the coating layer has an island form in which the surface of the core particle is coated with the cobalt-based compound having a rock salt crystal structure.
5. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
a weight ratio (core particle:coating layer) of the core particle to the coating layer is 1,000:0.2 to 1,000:10.
6. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
a thickness of the coating layer is 1 to 50 nm.
7. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
a D50 particle diameter of the coating particle is 12 to 25 μm.
8. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
when the battery is stored at a temperature range of 50 to 80° C. for one week and then discharged at a voltage of 4.4 V, a Co elution amount per 1 g of the positive electrode active material is 100 to 200 ppm/g.
9. A lithium rechargeable battery, comprising:
a positive electrode containing the positive electrode active material of claim 1 ;
an electrolyte; and
a negative electrode.
10. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein the second region is a mixed structure of the spinel structure and the layered structure from an interface with the first region to the surface of the core particle.
11. The positive electrode active material for a lithium rechargeable battery of claim 1 , wherein:
when the battery is stored at a temperature of 60° C. for one week and then discharged at a voltage of 4.5 V, a Co elution amount per 1 g of the positive electrode active material may be 1,500 to 2,500 ppm/g.