Preparation of LiCoO 2 from spent lithium-ion batteries

Abstract

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 LiCoO 2 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 HNO 3 solution is found to be an effective reducing agent by enhancing the leaching efficiency. Of the many possible processes to produce LiCoO 2, 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 LiCoO 2 with nitric acid, the molar ratio of Li to Co in the leach liquor is adjusted to 1.1 by adding a fresh LiNO 3 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 LiCoO 2 is successfully obtained. The particle size and specific surface-area of the resulting crystalline powders are 20 μm and 30 cm 2 g −1, respectively. The LiCoO 2 powder is found to have good characteristics as a cathode active material in terms of charge–discharge capacity and cycling performance.