Positive electrode active material for lithium secondary battery, comprising lithium cobalt oxide for high voltage, and method for preparing same

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.