Abstract
To promote the recycling of lithium-ion batteries, it is essential to develop pretreatment technologies that can efficiently delaminate and recover electrode layers containing active materials. In this study, we investigated the applicability of an underwater ultrasonic delamination technique, proposed by the authors, to used cells and commercial batteries. Ni–Co–Mn (NCM) ternary oxide cathodes were used to compare delamination behavior before and after charge/discharge cycles. After cycling, delamination was facilitated by the formation of aluminum fluoride (AlF3) at the interface between the aluminum (Al) current collector and the cathode material. Furthermore, underwater ultrasonic treatment was applied to cathodes from four types of commercial cylindrical cells. While some electrodes were difficult to delaminate by ultrasonic treatment alone, delamination rates exceeding 95% were achieved when combined with a preheating step at 200–400°C. Analysis of the polyvinylidene fluoride (PVdF) binder content and cutting strength of the cathode material revealed that preheating reduced binder adhesion strength. Under these conditions, cavitation impacts generated during ultrasonic treatment effectively acted on both the internal structure of the cathode material and the cathode material/Al foil interface, thereby promoting separation and delamination. Overall, these results demonstrate that underwater ultrasonic treatment, when combined with appropriate pretreatment conditions, can be applied to various commercial spent electrodes with different structures, materials, and degradation states. The technique is expected to offer high adaptability in actual recycling processes, contributing to the expansion of applicability and improved efficiency of the overall recycling workflow.
