Patent ID: 8481213

Claim:
A cathode active material for a lithium secondary cell, comprising a lithium transition metal oxide with a layered crystalline structure in which the transition metal comprises a transition metal mixture of Ni, Mn and Co, an average oxidation number of all transition metals other than lithium is more than +3, and specific conditions represented by the following Formulae (1), (2) and (3) are satisfied: 1.1< m (Ni)/ m (Mn)<1.5 (1) 0.4< m (Ni 2+ )/ m (Mn 4+ )<1 (2) 0.11< m (Ni 3+ )/ m (Mn)≦0.06 (3) wherein the nickel portion of the mixture comprises nickel (a) in an excess content relative to a content of manganese, as well as nickel (b) with a content corresponding to the content of manganese, and wherein m(Ni)/m(Mn) is a molar ratio of nickel to manganese, m(Ni 3+ )/m(Mn) is a molar ratio of Ni 3+ of nickel (b) to Mn, and m(Ni 2+ )/m(Mn 4+ ) is a molar ratio of Ni 2+ to Mn 4+ .