10. A method for preparing a transition-metal composite oxide, the method comprising:
forming a first aqueous metal-salt solution with nickel, manganese, and cobalt;
forming a second aqueous metal-salt solution with nickel, manganese, and cobalt;
mixing a basic solution and an ammonia solution in a reactor to adjust pH of a reactant to 11.8 through 12.3; and
supplying a first mixed aqueous metal-salt solution, which is formed of the first aqueous metal-salt solution and the second aqueous metal-salt solution, and ammonia and basic solutions into the reactor,
wherein a mixing ratio of the first aqueous metal-salt solution and the second aqueous metal-salt solution in the first mixed aqueous metal-salt solution is equal to or higher than 0 v % and equal to or higher than 100 v %.
ammonia solution in a reactor
pH
to 11.8 through 12.3