Preparation of LiCoO2 from spent lithium-ion batteries

A recycling process involving mechanical, thermal, hydrometallurgical and sol–gel steps has been applied to recover cobalt and lithium from spent lithium-ion batteries and to synthesize LiCoO₂ from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt can be concentrated with a two-step thermal and mechanical treatment. The leaching behavior of lithium and cobalt in nitric acid media is investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO₃ solution is found to be an effective reducing agent by enhancing the leaching efficiency. Of the many possible processes to produce LiCoO₂, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO₂ with nitric acid, the molar ratio of Li to Co in the leach liquor is adjusted to 1.1 by adding a fresh LiNO₃ solution. Then, 1 M citric acid solution at a 100% stoichiometry is added to prepare a gelatinous precursor. When the precursor is calcined at 950 °C for 24 h, purely crystalline LiCoO₂ is successfully obtained. The particle size and specific surface-area of the resulting crystalline powders are 20 μm and 30 cm² g⁻¹, respectively. The LiCoO₂ powder is found to have good characteristics as a cathode active material in terms of charge–discharge capacity and cycling performance.