The electrochemical properties of cells assembled with the LiNiO₂ (LNO) recycled from cathode materials of waste lithium secondary batteries (Li[Ni,Co,Mn]O₂), were evaluated in this study. The leaching, neutralization and solvent extraction process were applied to produce high-purity NiSO₄ solution from waste lithium secondary batteries. High-purity NiO powder was then fabricated by the heat-treatment and mixing of the NiSO₄ solution and H₂C₂O₄. Finally, LiNiO₂ as a cathode material for lithium ion secondary batteries was synthesized by heat treatment and mixing of the NiO and Li₂CO₃ powders. We assembled the cells using the LiNiO₂ powders and evaluated the electrochemical properties. Subsequently, we evaluated the recycling possibility of the cathode materials for waste lithium secondary battery using the processes applied in this work.