Sustainable and efficient deep eutectic solvents in recycling of spent lithium-ion batteries: recent advances and perspectives

Limited cycling life and outdated recycling modes will inevitably cause an explosive surge in spent lithium-ion batteries (LIBs). The recycling and reutilization of these spent LIBs play a vital role in environmental conservation and resource circulation. In recent years, deep eutectic solvents (DESs), recognized as green solvents, have attracted the public's attention for their outstanding environmental friendliness, recyclability, tunability, and ability to dissolve metal oxides, which has resulted in significant practical value in the realm of recycling spent LIBs, offering enormous economic feasibility for the large-scale recovery and utilization of spent LIBs. This paper offers a comprehensive overview of recycling technologies within the recent DESs system, focusing on the separation of cathode active materials (CAMs) and current collectors, as well as the extraction of metals from CAMs. Firstly, this review systematically expounds on the distinctions in the separation principles of DESs when separating CAMs and current collectors. Secondly, the leaching system is preliminarily categorized, considering the composition of DESs. It methodically delineates and compares the advantages, challenges, and leaching mechanisms of different DES leaching systems from perspectives on viscosity, acidity, reducibility, and coordination ability. On this basis, a preliminary proposal for an efficient, low-cost, green, and sustainable spent LIBs recycling process under the DESs system is introduced, offering a reference for improving spent LIBs recycling technology under the DESs system. Finally, the current challenges of DESs in recycling spent LIBs are discussed, and relevant suggestions for the future direction in this field are proposed.