Towards Sustainable Direct Recycling: Unraveling Structural Degradation Induced by Thermal Pretreatment of Lithium-Ion Battery Electrodes.

Abstract

As the demand for lithium-ion batteries (LIBs) continues to increase, there is a growing focus on recycling these battery wastes. Among the existing recycling methods, direct recycling is considered a promising approach, because it allows waste to be returned directly to production. One crucial step is the pretreatment, which involves separating the active materials from the current collector. Thermal treatment provides a feasible and effective approach for achieving this separation. However, there are still concerns regarding the potential impact of this process on the structure and composition of electrodes. This study aims to examine the effects of thermal treatment on the separation efficiency and crystal structure of fresh and cycled NMC (LiNi0.6Co0.2Mn0.2O2) cathodes and graphitic anodes, under different atmospheres and temperatures. According to the research findings, 350°C is the lowest temperature required for complete separation of cathode materials in an oxygen atmosphere, with only minor structural degradation. In the case of graphite, thermal treatment under argon, nitrogen and hydrogen demonstrates good structural stability. However, for cycled anodes, the desired separation is not achieved due to the possible interface adhesion that occurs during cycling and heating. Additionally, compared to fresh materials, cycled materials experience more pronounced structural degradation during thermal treatment.