Deep Eutectic Solvents for Efficient and Sustainable Recycling of Spent Lithium-Ion Batteries: Fundamental Research, Process Intensification, and Future Prospect

Abstract

The development of new energy vehicles has generated a surplus of spent lithium-ion batteries (LIBs), leading to the urgency for recycling spent LIBs. Deep eutectic solvents (DESs), a versatile green liquid, hold broad promise for recycling spent LIBs. This review summarizes the fundamental research progress of LIBs recycling via DESs in pretreatment, hydrometallurgy, and direct regeneration. However, the practical application of DESs is hindered by inherent drawbacks, including high viscosity and detrimental side reactions such as esterification between the hydroxyl and carboxyl groups in the DESs components. To bridge this gap, process intensification technologies for recycling LIBs using DESs are summarized. On the one hand, various process intensification technologies are being rapidly developed to improve the efficiency of DESs. These include chemical methods, such as the addition of cosolvents to improve mass transfer and reducibility, and the design of ternary DESs that integrate a hydrogen bond acceptor and a hydrogen bond donor to tailor solvent properties, as well as physical methods, such as microwave, ultrasound, high-pressure, and flash joule heating. On the other hand, advanced computational approaches involving simulation and artificial intelligence are increasingly being adopted. These approaches empower the rational design of high-performance DESs. Moreover, to balance environmental friendliness and economic considerations, we focus on analyzing DESs recycling strategies and the methodological value of life cycle assessment for evaluating environmental and economic benefits. This review outlines and analyzes prospects, guiding the development of recycling technologies to achieve efficient and sustainable LIBs recycling.