Enhanced Recovery of Valuable Materials from Spent Lithium‐Ion Secondary Batteries Using Organic Acids as Leaching and Precipitating Agents

Abstract In this study, the cathode active material was first separated from the aluminum foil through a heat treatment at 500 °C. The separated cathode active material was calcined at a temperature of 1000 °C to remove completely carbon particles generated from the organic adhesive during heat treatment. Then, Co, Mn, and Ni were recovered from the cathode active material using lactic acid and oxalic acid as leaching and precipitating reagents. The lactic acid showed almost similar metal leaching effects from cathode active material compared to sulfuric acid, hydrochloric acid, and nitric acid. The optimal metal leaching efficiency by lactic acid was obtained when 30 g of the cathode active material was added to the 2 N lactic acid solution. At these conditions, the leaching efficiencies of Li, Mn, Co, and Ni were 90.4%, 89.2%, 92.2%, and 91.8%, respectively. Subsequently, when 5 g of oxalic acid was added to the lactic leachate of 2 N, a phenomenon in which all metals were precipitated was observed. Based on this result, the optimal condition for precipitating the leached metals using oxalic acid was oxalic acid/cathode active material = 1:7 (w/w %). Through XRD and EDX analysis, the precipitate was identified as a polynuclear crystalline material (NiCoMnC 2 O 4 ·2H 2 O) in which the three components of Mn, Co, and Ni oxalates were mixed with approximately 7:4:10 in integer ratio of weight. The produced precipitate can be recycled as a raw material of cathode active material through simple heat treatment.