Mechanical and Ultrasonic Pretreatments for Efficient Peeling of Metal Foils from Spent Lithium-Ion Batteries

Typical recycling processes of electrode materials of spent lithium-ion batteries are complicated, energy-consuming, have limited separation efficiency, and cause environmental issues. Therefore, examining various environmental approaches, such as physical pretreatments, would be essential to enhance recycling efficiency. As a novel approach in this study, the ultrasonic treatment and mechanical stirring were examined to explore the potential of selective stripping of cathode and anode materials of spent lithium-ion batteries. The effects of various factors on the stripping efficiency and selectivity were assessed (ultrasonic power, mechanical stirring speed, processing time, and temperature). Outcomes indicated that the cavitation generated by ultrasound and mechanical stirring could impact the diffusion process of the aqueous medium. This phenomenon could lead to a high peeling performance of electrode materials, while this effect would be more evident as the intensity of the corresponding parameter was increased. Generally, the overall peeling efficiency for anode materials was higher than for cathode ones in various conditions. Mechanical stirring speed could improve the peeling efficiency of cathode materials. Experimental outcomes demonstrated that the corrosion of metal foils would appear by increasing the intensity of corresponding parameters. Combining ultrasound and mechanical stirring could markedly enhance the peeling efficiency of both cathode and anode materials. In other words, combining these treatments would decrease the peeling selectivity. Various characterizations, such as scanning electron microscope and energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray fluorescence, were applied to verify the experimental outcomes.