| abstract |
Provided is a lithium transition metal oxide having an α-NaFeO 2 layered crystal structure, as a cathode active material for lithium secondary battery, wherein the transition metal includes a blend of Ni and Mn, an average oxidation number of the transition metals except lithium is +3 or higher, and the lithium transition metal oxide satisfies Equations 1 and 2:n n1.0< m (Ni)/ m (Mn) (1)n n m (Ni 2+ )/ m (Mn 4+ )<1 (2)n nwherein m(Ni)/m(Mn) represents a molar ratio of nickel to manganese and m (Ni 2+ )/m (Mn 4+ ) represents a molar ratio of Ni 2+ to Mn 4+ . The cathode active material of the present invention has a uniform and stable layered structure through control of oxidation number of transition metals to a level higher than +3, in contrast to conventional cathode active materials, thus advantageously exerting improved overall electrochemical properties including electric capacity, in particular, superior high-rate charge/discharge characteristics. |