A uniform Al-doped LiNi_0.5Co_0.2Mn_0.3O₂ cathode material was prepared using a coprecipitation method to take advantage of the positive effect of Al on regenerated NCM (Ni, Co, Mn) cathode materials and ameliorate cumbersome and high-cost impurity removal processes during lithium-ion battery recycling. When the Al³⁺ content in the leachate was 1 at.% with respect to the total amount of transition metals (Ni, Co, and Mn), the produced Al-doped NCM cathode material increased concentrations of lattice oxygen and Ni²⁺. The initial specific capacity at 0.1C was 167.4 mA·h/g, with a capacity retention of 79.1% after 400 cycles at 1C. Further, this Al-doped sample showed improved rate performance and a smaller electrochemical impedance. These findings provide a reference for developing industrial processes to resynthesize cathode materials with improved electrochemical performance by incorporating Al³⁺ impurities produced during lithium-ion battery recycling.