| dc.description.abstract | This study mainly combines two types of deep eutectic solvents (DESs), choline chloride:lactic acid (ChCl:LA) and choline chloride:oxalic acid (ChCl:OA), for the separation and recovery of graphite, nickel, and cobalt from waste lithium battery powder, also known as black mass (BM). The temperature and composition of the recovery process are discussed.
In this research, the separation process consists of three steps. In the first step, we dissolve the majority of metal ions in the leaching solution using ChCl:LA, while the main element graphite in the black powder is retained in the 1st precipitate. Then, in the second step, we add OA or ChCl:OA for the reaction. We found that adding ChCl:OA and reacting at a high temperature of 120℃ achieves the best separation efficiency for Ni and Co. This is because the high-temperature environment and the chloride ions provided by ChCl:OA help stabilize the [CoCl4]2- structure, allowing Co to dissolve in the 2nd leaching solution, while Ni combines with OA to form NiC2O4·2H2O. In the third step, we add H2O to induce a coordination structure change in [CoCl4]2-. Due to the low solubility of CoC2O4·2H2O in water, Co ultimately precipitates as CoC2O4·2H2O.
In conclusion, this study demonstrates a more environmentally friendly way to recycle the black mass compared to conventional methods. Through this procedure, we are able to separate both cathode and anode materials from the black mass. The regenerated anode, synthesized from the recovered graphite, exhibits good electrochemical performance, with a discharge specific capacitance of 227.5 mAh/g at a current density of 1C (1C=372mA/g) after 500 cycles. The recovery efficiency of cobalt can reach 85%, and the material obtained after calcination is Co3O4, which can be used as a precursor for synthesizing cathode materials. The materials recycled from this procedure demonstrate excellent reusability, thus contributing to the achievement of the goal of material sustainability. | en_US |