The cathode materials of spent NCM523 lithium-ion batteries contain valuable metal elements such as Ni and Co, which must be recycled. Ni and Co in cathode electrode active materials were first leached with H₂SO₄ and H₂O₂. Then Mn was removed by adding KMnO₄ into the leaching solution. Finally NiCoO₂ powders were prepared from the purified solution. The effects of various factors on metal leaching rates were analyzed. Under the conditions of H₂SO₄ concentration 2.5 mol/L, H₂O₂ volume fraction 10%, leaching temperature 80℃, leaching time 80 min and solid-liquid ratio 1:14 g/mL, the leaching rates of Ni, Co and Mn were 94.03%, 99.56% and 14.97%, respectively. Hence the separation of Mn from Ni and Co was obtained by selective leaching of Ni and Co. Using KMnO₄ as oxidant, the residual ionic Mn in the leachate was lower than 0.45 mmol/L. Chain-like NiCoO₂ with uniform morphology was prepared from the purified leaching solution by hydrothermal synthesis at 160℃ and calcination at 400℃, using polyethylene glycol PEG-2000 as surfactant and oxalic acid as precipitant. Therefore, the recycling of valuable metals Ni and Co in cathode materials of waste batteries was realized.