Recycling and Reutilization of Metals Aided by Deep Eutectic Solvents: from NMC Cathodes of Spent Li‐ion Batteries to Electrolytes for Supercapacitors

With the rapidly increasing demand for lithium ion batteries (LIBs), recycling the metals found in spent cathodes is mandatory to both alleviate shortages resulting from the mining of natural metal ores and manage the disposal of spent LIBs. The use of deep eutectic solvents (DESs) for metals recovery from spent cathodes of LIBs (e. g., LCO and NMC types) offers a sustainable yet efficient alternative to conventional hydrometallurgical processes. Nonetheless, g efforts are required to use milder temperatures and higher mass loadings, thus ensuring cost‐effectiveness. In this latter regard, addressing the reutilization of DESs in subsequent stages of metal extraction, and streamlining or eliminating the chemical procedures employed for metal separation, is even more crucial to guarantee the economic feasibility of the recycling process. Herein, we have prepared a DES that provides extraction efficiencies of ca. 100 % for every metal of NMC cathodes even at mild experimental conditions (e. g., 60 °C) and for loadings as high as 70 mgNMC/gDES. Moreover, we have pioneered the direct use of leachates containing DESs and metals as electrolytes for supercapacitors. This approach enables the reintroduction of DESs and the recovered metals into the value chain with a minimal economic and environmental impact. The use of DESs for metals recovery from spent cathodes of LIBs may offer a sustainable alternative to conventional hydrometallurgical processes as long as the matter of DES recovery and/or reutilization is circumvented. The reintroduction of DES and the recovered metals as electrolytes for supercapacitors marks a pioneering paradigm shift in closing the loop within the realm of electrochemical energy storage