Herein, a preparation method of a Ni-rich cathode material in a lithium-ion battery is presented. Using the separate addition of Al hydroxide sol to a Ni/Co sulfate solution, monodispersed large particles of Ni0.8Co0.15Al0.05 hydroxide were prepared in a shorter retention time within a continuously stirred tank reactor. The electrochemical test of a cathode fabricated with as-prepared material exhibited a good discharge capacity (190 mA g(-1)), high initial efficiency (90.3%), high rate capability, and stable cyclability even though it was composed of larger particles. The improved performances in this work were probably attributable to the uniform dispersion of Al atoms within LiNi0.8Co0.15Al0.05O2 particles and the well-developed layered structure.