A novel method for screening deep eutectic solvent to recycle cathode of Li-ion batteries
Deep eutectic solvents (DESs), as a green alternative technology, exhibited a great potential to recycle valuable elements from spent lithium-ion batteries (LIBs). However, due to its weak reduction power of DESs, raising temperature and extending processing duration were not efficient for screening suitable DESs for recycle of LIBs. Here, we proposed a novel, simple and robust experimental method to identify suitable DESs for recycling of spent LIBs. Based on the electrochemical principle, the method proposed in this study could quickly determine the reduction power of DESs. As an example, a choline chloride (ChCl) and urea mixture as a DES possessed a strong reducibility with a Li and Co extraction efficiency of 95% from spent LIBs being obtained at the reduced reaction temperature of 180°C and reaction time of 12 h. The results are in good agreement with the results from Fukui functions calculations. The kinetic experiments revealed that the Li and Co extraction was controlled by the solution diffusion and electron diffusion through the DES. Furthermore, a cubic cobalt oxide spinel (Co3O4) was obtained from the loaded DES by H2C2O4 and NaOH in the dilution-precipitation-calcining process. The current strategy demonstrates great potential for rapid and reliable screening suitable DESs for effective recycle of spent LIBs.