Heavy liquids for rapid separation of cathode and anode active materials from recycled lithium-ion batteries

Lithium-ion batteries (LIBs) dominate the industry of rechargeable batteries in recent years due to their advantages, including high energy and power density and relatively long lifespan. Despite these advantages, the disposal of spent LIBs into the ground is harmful to the environment, which needs to be addressed by recycling spent LIBs. The available recycling methods for spent LIBs such as pyrometallurgy and hydrometallurgy focus only on collecting valuable elements from the spent LIBs. The direct physical recycling method may be more economical than the other two methods if the mixed cathode and anode active materials are separated, directly regenerated, and then used to make new LIBs. The first obstacle in this method is the separation of different types of spent active materials that came in the form of micro-sized powder (filter cake). This study aims to separate the mixture of cathode and anode active materials by adopting Stokes' law. The focus is on the physical separation rather than the thermal or chemical separation methods to avoid damaging the morphology and composition of electrode active materials. The proposed mathematical model shows how fast and effectively different electrode materials can be separated by adjusting the heavy liquid density. For validation, several experiments are conducted to separate the cathode active materials (LiCoO2, LiFePO4, LiNi0.8Co0.15Al0.05O2, LiNi1/3Co1/3Mn1/3O2, and LiMn2O4) and the anode active material (Graphite) from each other. Overall, this study shows how rapidly and effectively (high purity) electrode active materials can be separated without damaging the morphology and the composition of electrode active materials.