Sustainable leaching of critical metals from lithium ion battery black mass using a citric acid and choline chloride deep eutectic solvent

Abstract The recycling of lithium-ion batteries (LIBs) is of critical importance due to the increasing demand for electric vehicles and portable electronic devices. It also helps address supply risks of critical raw materials and reduces the environmental impact of mining. Traditional recycling methods are often inefficient and environmentally damaging. This study investigates the use of deep eutectic solvents (DES), made from citric acid and choline chloride, for leaching valuable metals from black mass derived from spent LIBs. The research focuses on optimizing the leaching parameters, such as temperature, DES ratio, and solid-to-liquid ratio, to maximize the extraction efficiency of lithium, cobalt, nickel, and manganese. A key aspect of the study was the examination of the rheological properties of the DES system, as these properties significantly impact the leaching process. The viscosity and pH of the DES were measured, providing insights into their behavior under various conditions. Understanding the viscosity and flow characteristics of these DES systems is crucial for developing scalable and effective recycling methods. The DES mixture with a 2:1 ratio of citric acid to choline chloride, mixed with 50% water, showed the best performance. At 90 °C for 24 h, this DES mixture achieved leaching efficiencies of 77.5% for lithium, 79.9% for cobalt, 80% for manganese, 66.2% for nickel, 82.5% for copper, and 93.8% for aluminum. These findings suggest the potential of citric acid-choline chloride DES as a sustainable and environmentally friendly reagent for recycling LIBs.