9. A method of preparing a positive active material for a lithium secondary battery, the method comprising:
a first process for mixing a first precursor solution comprising a nickel salt, a cobalt salt, and a manganese salt, at a molar ratio of x:y:z satisfying 0.05≤x≤0.9, 0.1≤y≤0.8, 0.1≤z≤0.8, and a first base, to prepare a first mixture and inducing a reaction in the first mixture to obtain a precipitate;
a second process for adding to the precipitate a second precursor solution comprising a nickel salt, a cobalt salt, and a manganese salt, at a molar ratio of x':y':z' satisfying 0.05≤x'≤0.9, 0.1≤y'≤0.8, 0.1≤z'≤0.8, and x'+y'+z'=1, and a second base, to obtain a second mixture and inducing a reaction in the second mixture to obtain a nickel-based composite hydroxide; and
mixing the composite metal hydroxide with a lithium salt and heat treating the mixed composite metal hydroxide to prepare the positive active material according to any one of claims 1 to 8,
wherein the content of nickel in the first precursor solution is adjusted to be larger than the content of the second precursor solution,
wherein the reaction time of the second mixture in the second process is adjusted to be longer than the reaction time of the first mixture in the first process, and
wherein a pH of the first mixture in the first process is adjusted to be in a range of 10 to 11, and a pH of the second mixture in the second process is adjusted to be in a range of 11.5 to 12.0.
the first process
pH
a range of 10 to 11
the second process
pH
a range of 11.5 to 12.0