Lithium-nickel-manganese composite oxide, processes for producing the same, and use of the same

Abstract

A subject for the invention relates to providing a positive active material for lithium ion secondary batteries which attains a high discharge capacity and is excellent in rate characteristics and cycle characteristics. A feature of the invention resides in that a lithium-nickel-manganese composite oxide which has a composition represented by LixNiyMnzO2 wherein x is 1+1/9±(1+1/9)/10, y is 4/9±(4/9)/10, and z is 4/9±(4/9)/10, in particular, represented by the general formula Li[Ni0.5-0.5XMn0.5-0.5XLiX]O2 wherein X satisfies 0.05≦X≦0.11, and has a crystal structure belonging to the monoclinic system and having a space group of C12/ml (No. 12) is used as a positive-electrode material. The lithium-nickel-manganese composite oxide preferably is one in which in X-ray powder diffractometry using a Cu—Kα ray, the peak intensity ratio I(002)/I(13-3) between the (002) plane and the (13-3) plane in terms of Miller indexes hkl on the assumption of belonging to C12/ml (No. 12) of the monoclinic system is 1.35 or higher.

Dependencies are inferred from the claim text.