Engineering classification recycling of spent lithium-ion batteries through pretreatment: a comprehensive review from laboratory to scale-up application

The lithium-ion batteries (LIBs) have been widely equipped in electric/hybrid electric vehicles (EVs/HEVs) and the portable electronics due to their excellent electrochemical performances. However, a large number of retired LIBs that consist of toxic substances (e.g., heavy metals, electrolytes) and valuable metals (e.g., Li, Co) will inevitably flow into the waste stream, and their incineration or landfill treatment will cause severe risks to ecosystem and human beings. The sustainable and efficient treatment or recycling of valuable resources from spent LIBs should be fully recognized for environmental and resource security. As one of the most important processes for spent LIBs recycling, the pretreatment is an indispensable step, which is directly related to the subsequent metal extraction and separation processes. Although considerable progresses have been made regarding the pretreatment technologies, there are few summarized reports concerning critical processes of spent LIBs recycling, especially combination of currently available recycling technologies with industrialized applications during pretreatments. Therefore, comprehensive review of the current prevailing pretreatment technologies in laboratory to existing scale-up applications is quite necessary to reveal cutting-edge development in the field of pretreatment. In this review, the current pretreatment technologies are systematically categorized and introduced, along with critical discussions. This review focused on the various options for pretreatment processes itself, instead of general spent LIBs recycling technologies without the focused topics that have been sophisticatedly reviewed by previous studies. Here, the deactivation, discharge, dismantling, separation, liberation of active material and electrolyte treatment have been summarized with the in-depth discussion of the technology development and current status of each category. Finally, current states of industrial development are also reviewed and discussed for the development of efficient and environmentally friendly recycling technologies for future applications. This review tends to present a focused topic concerning the pretreatment of spent LIBs to potential readers with a comprehensive illustration of the development on both cutting-edge technologies and scale-up applications. Graphical abstract