Water-regulated deep eutectic solvents for sustainable closed-loop recycling of spent lithium cobalt oxide

Abstract

Deep Eutectic Solvents (DESs) are regarded as a novel class of green solvents for the recycling of spent lithium-ion batteries (LIBs). However, their high viscosity, the challenge in selective metal separation, and the difficulty of high-value utilization still hinder further applications of DESs. Herein, we present a novel H₂O-regulation method for the selective recovery of Co and Li from spent LiCoO₂ (LCO) using a low-viscosity DES, which comprises carbon-rich tannic acid (TA), choline chloride (ChCl), and H₂O (for dilution). After the efficient leaching process, only extra water is used for the precipitation of Co to form a TA–Co complex, owing to the good coordination ability of TA. Notably, TA–Co complexes can be converted into high-value catalysts (Co@C) directly via calcination based on the carbon-rich structure of TA, which exhibits promising OER catalytic performance, further proving the proposed process to be a sustainable method for recycling spent LIBs.