11. The active material of claim 1, wherein the active material precursor is obtained by a method comprising:
mixing a nickel precursor, a manganese precursor, a cobalt precursor, a metal (M) precursor, and a solvent to prepare a precursor mixture; and
mixing the precursor mixture and a pH adjusting agent to adjust a pH value of the resultant to be in a range of about 11.0 to about 11.2.
pH
range of about 11.0 to about 11.2