Deep Eutectic Solvents: Green Approach for Cathode Recycling of Li-Ion Batteries

The overarching demand of modern electronics and electrification of transportation has tremendously increased usage of rechargeable lithium-ion batteries (LIBs). As a result, massive amounts of solid waste are generated from the end-of-life LIBs and expected to increase by two- to threefolds in the near future. Without proper recycling strategies and infrastructure, the immediate threat of environmental pollution and wastage of resources is clear. One way to circumvent these challenges is to recycle the spent LIBs and recover the components and materials, especially heavy metals for future repurposing applications. This review highlights the recent discoveries on the use of deep eutectic solvents (DESs) as an economical and environmentally friendly medium for metal recovery from spent LIBs. Herein, how the different hydrogen donors and acceptors affect the overall performance of DES in terms of leaching efficiency, time, temperature, and metal recovery rates are outlined. Very importantly, the mechanism of metal leaching from the metal oxides using DES is discussed. Finally, some potential strategies and opportunities for further development of novel DES for metal-recovery from not only spent LIBs but also other industries such as, mining, oil, and agriculture are outlined.