Positive electrode active material for lithium secondary battery, comprising lithium cobalt oxide for high voltage, and method for preparing same
The present invention provides a positive active material for a rechargeable lithium battery, the active material including a dopant and having a crystalline structure in which metal oxide layers (MO layers) including metals and oxygen and reversible lithium layers are repeatedly stacked, wherein in a lattice configured by oxygen atoms of the MO layers adjacent to each other, the dopant time of charge, thereby forming a lithium trap and/or lithium dumbbell structure.
1. A positive active material for a rechargeable lithium battery comprising lithium cobalt oxide particles,
wherein the lithium cobalt oxide particles include a dopant, wherein the dopant is Mg, and a Mg concentration of an outer bulk of a particle surface to 0.9*r is relatively higher than the Mg concentration of an inner bulk of 0.9*r to a particle center, wherein r is an average radius of the lithium cobalt oxide particle;
the lithium cobalt oxide particles have a crystalline structure in which metal oxide layers (MO layers) including metals and oxygen and reversible lithium layers in which lithium ions move reversibly at the time of charge and discharge are repeatedly stacked, and
the dopant and/or lithium ions move from octahedral sites to tetrahedral sites at the time of charge in a lattice configured by oxygen atoms of the MO layers adjacent to each other, thereby forming a lithium trap and/or a lithium dumbbell structure and providing structural stability at a high voltage of 4.5 V or greater,
and wherein the lithium cobalt oxide particles are further coated with protective chemicals,
the protective chemicals are at least one of a metal, an oxide, a phosphate salt, or a fluoride, and the protective chemicals do not include Ti.
2. The positive active material of claim 1 , wherein the dopant is included in an amount of 0.001 to 1 wt % based on a total weight of the lithium cobalt oxide particles.
3. The positive active material of claim 1 , wherein the lithium trap structure is a structure in which the lithium ions are disposed in tetrahedral sites at the time of charge in a lattice configured by oxygen atoms of a first MO layer and a second MO layer adjacent to each other.
4. The positive active material of claim 1 , wherein the lithium dumbbell structure is a structure in which lithium ions are disposed in tetrahedral sites between a first MO layer and a second MO layer, and the dopants are disposed in tetrahedral sites between the second MO layer and a third MO layer at the time of charge in a lattice configured by oxygen atoms of the first MO layer, the second MO, and the third MO layer, so the lithium ions and the dopants are symmetrically disposed in a center of the second MO layer.
5. The positive active material of claim 1 , wherein the positive active material comprises a lithium trap and a lithium dumbbell structure.
6. The positive active material of claim 1 , wherein the positive active material comprises a lithium trap structure.
7. The positive active material of claim 1 , wherein the lithium trap or the lithium dumbbell structure suppresses a phenomenon of relatively sliding of the MO layers by a repulsive force generated among metals of the MO layer, lithium of the tetrahedral site, and the dopants which are each cations, thus suppressing a structural change.
8. The positive active material of claim 1 , wherein the lithium cobalt oxide particles further comprise at least one selected from the group consisting of Ca, Al, and Sb as a dopant.
9. The positive active material of claim 1 , wherein the protective chemicals are included at 0.02 wt % to 0.8 wt %.
10. The positive active material of claim 1 , wherein the protective chemicals have a thickness of 30 nm to 250 nm.
11. The positive active material of claim 1 , wherein the lithium cobalt oxide particles have a medium particle size (D50) of 5 micrometers to 25 micrometers.