A positive active material for non-aqueous electrolyte secondary battery is provided
comprising lithium manganese oxide having such a spinel structure that the half-width
(2) of the reflection peak corresponding to 440 plane as determined by X-ray
diffractometry using CuK ray is not greater than 0.145. The use of
this positive active material makes it possible to obtain a secondary battery which
exhibits a good cycle life performance at room temperature and high temperatures
and a reduced capacity drop when stored at high temperatures.
