Positive electrode active material, non-aqueous electrolyte secondary cell and method for preparation thereof

A non-aqueous electrolyte cell having improved cyclic characteristics at elevated temperatures. The non-aqueous electrolyte cell includes a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode contains, as a positive electrode active material, a lithium transition metal composite oxide represented by the general formula LiCoABO where A denotes at least one selected from the group consisting of Al, Cr, V, Mn and Fe, B denotes at least one selected from the group consisting of Mg and Ca and x, y and z are such that 0.9 ≤x< 1, 0.001 ≤y≤ 0.05 and 0.001