A promising physical method for recovery of LiCoO2 and graphite from spent lithium-ion batteries: Grinding flotation

Due to the limitation of secondary pollution and high equipment investment, the industrial-scale recycling technology for electrode materials from spent lithium-ion batteries (LIBs) needs urgent breakthrough. In this paper, a physical recycling method, grinding flotation, is creatively proposed for the separation and recovery of LiCoO2 and graphite from spent LIBs. According to the exploratory experiments, if the mixed electrode materials is ground in the hardgrove machine for 5 min before reverse flotation, the concentrate grade of LiCoO2 sinks and graphite floats can reach 97.13% and 73.56%, respectively. Moreover, with the help of advanced analytical technologies, the surface morphology, elemental chemical states and element distribution on the very surface of electrode particles before and after grinding were systematically analyzed to reveal the mechanism of dry surface modification. Results indicate that the mechanical grinding destroys the lamellar structure of graphite, exposing massive newborn hydrophobic surfaces. Meanwhile, the abrasion of organic film coating the LiCoO2 particles causes its original hydrophilic surface partially regained. Hence, the great wettability difference between LiCoO2 and graphite contributes to an excellent flotation separation. This grinding flotation method is a promising separation method without any toxic emissions or introducing other impurities in industrial application.