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Abstract

Provided is a lithium transition metal oxide having an α-NaFeO₂ 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:

description='In-line Formulae' end='lead'1.0<m(Ni)/m(Mn)  (1)description='In-line Formulae' end='tail'

description='In-line Formulae' end='lead'm(Ni²⁺)/m(Mn⁴⁺)<1  (2)description='In-line Formulae' end='tail'

wherein m(Ni)/m(Mn) represents a molar ratio of nickel to manganese and m (Ni²⁺)/m (Mn⁴⁺) represents a molar ratio of Ni²⁺ to Mn⁴⁺. 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.

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First Claim