Fluorine-containing positive electrode active material for lithium secondary battery, and lithium secondary battery including same

A positive electrode active material for a lithium secondary battery having a layered structure and containing lithium, a transition metal, fluorine (F) and oxygen,

• wherein the layered structure comprises a lithium layer consisting of only lithium, and a transition metal layer consisting of only a transition metal including nickel,
• wherein the nickel comprises Ni3+ and Ni2+ in terms of oxidation number, and a ratio of the Ni2+ to the Ni3+ (Ni2+/Ni3+) increases with increasing content of the fluorine,
• wherein the layered structure further comprises a first mixed layer and a second mixed layer, each containing lithium and a transition metal, wherein the first mixed layer and the second mixed layer are stacked adjacent to each other and alternately and regularly repeated to form the layered structure, and the first and second mixed layers stacked adjacent to each other are configured such that the transition metal of the first mixed layer and the lithium of the second mixed layer correspond to each other, and
• wherein a lattice formed by the first and second mixed layers stacked adjacent to each other comprises a superlattice whose a-axis is twice as long as that of a lattice formed by the lithium layer and the transition metal layer.