Patent ID: 7393476

Claim:
A positive active material for lithium secondary batteries, comprising: a composite oxide comprising: an oxide which is represented by the composite formula Li x Mn a Ni b Co c O 2 and has an α-NaFeO 2 structure; and an impurity phase comprising Li 2 MnO 3 , wherein a, b, and c are values within such a range that in a ternary phase diagram showing the relationship among these, (a, b, c) is present on the perimeter of or inside the quadrilateral ABCD defined by point A (0.5, 0.5, 0), point B(0.55, 0.45, 0), point C (0.55, 0.15, 0.30), and point D(0.15, 0.15, 0.7) as vertexes, and 0.95<x/(a+b+c)<1.35.