Unveiling the Role and Mechanism of Mechanochemical Activation on Lithium Cobalt Oxide Powders from Spent Lithium-Ion Batteries

This research presented the impacts of mechanochemical activation (MCA) on the physiochemical properties of lithium cobalt oxide (LiCoO2) powders of cathode materials from spent lithium-ion batteries, and analyzed the relevant effects of these changes on the leaching efficiency of lithium and cobalt and the leaching kinetics of LiCoO2 powders. The results revealed the superiority of MCA in the following levels of changes in the LiCoO2 powders: first, the physical properties included a decrease in the average particle size, an increase in the specific surface area, and the appearance of a mesoporous structure change; second, changes in crystal-phase structures were reflected in the grain refinement of LiCoO2 powders, lattice distortions, lattice dislocations, and storage and increment of internal energy; third, the surface characteristics included a chemical shift of lithium element electrons, a reduction in Co3+ concentration, and an increment in the surface hydroxyl oxygen concentration. These changes in physiochemical properties and structures enhanced the hydrophilicity and interface reactivity of the activated LiCoO2 powders and significantly improved the leaching efficiencies of Li and Co in organic acid solutions. The rate-limiting step of metal leaching was also altered from a surface chemical reaction-controlled one before MCA to an ash layer diffusion-controlled one after MCA.