Aqueous-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, its high viscosity, the challenge in selective metal separation, and the difficulty of high-value utilization still hinder the further application of DES. 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.