A sustainable process for the recovery of valuable metals from spent lithium-ion batteries

In this work, an eco-friendly and hydrometallurgical process for the recovery of cobalt and lithium from spent lithium-ion batteries has been proposed, which includes pretreatment, citric acid leaching, selective chemical precipitation and circulatory leaching. After pretreatment (manual dismantling, N-methyl pyrrolidone immersion and calcination), Cu and Al foils are recycled directly and the cathode active materials are separated from the cathode efficiently. Then, the obtained cathode active materials (waste LiCoO₂) was firstly leached with 1.25 mol l⁻¹ citric acid and 1 vol.% H₂O₂ solution. Then cobalt was precipitated using oxalic acid (H₂C₂O₄) under a molar ratio of 1:1.05 (H₂C₂O₄: Co²⁺). After filtration, the filtrate (containing Li⁺) and H₂O₂ was employed as a leaching agent and the optimum conditions are studied in detail. The leaching efficiencies can reach as high as 98% for Li and 90.2% for Co, respectively, using filter liquor as leaching reagent under conditions of leaching temperature of 90°C, 0.9 vol.% H₂O₂ and a solid-to-liquid ratio of 60 ml g⁻¹ for 35 min. After three bouts of circulatory leaching, more than 90% Li and 80% Co can be leached under the same leaching conditions. In this way, Li and Co can be recovered efficiently and waste liquor re-utilization is achievable with this hydrometallurgical process, which may promise both economic and environmental benefits.