Green recycling of spent LiCoO 2 cathodes using a water-based deep eutectic solvent

Faced with the exponential growth of lithium-ion batteries (LIBs) and concomitant negative impact after retirement, it is imperative to explore green, efficient and closed-loop recycling of spent LIBs from the perspective of resource reutilization and environmental conservation. Herein, a water-based deep eutectic solvent (denoted as W-DES) composed of choline chloride (ChCl) and lactic acid (LA) is proposed for Co and Li recovery from spent LiCoO 2 cathode materials. Such an aqueous leaching system containing 1:3 M ratio of ChCl: LA diluted with 90 vol% H 2 O can effectively extract Li and Co from LiCoO 2 , yielding the respective 97.15 % and 95.20 % of leaching efficiency under the optimum conditions. After leaching, the dissolved cobalt and lithium species are recovered in the form of CoC 2 O 4 & sdot;2H 2 O and Li 2 CO 3 precipitates, which are further utilized for the insitu regeneration of LiCoO 2 . Remarkably, the regenerated LiCoO 2 possesses an excellent electrochemical performance, delivering an initial discharge specific capacity of 136.0 mAh/g at 0.5C and 87.43 % of capacity retention rate after 100 cycles, comparable to those of the commercially available LiCoO 2 , thus highlighting the feasibility of the proposed closed-loop recycling route.