An effective process for the recovery of valuable metals from cathode material of lithium-ion batteries by mechanochemical reduction

Abstract

To improve the recovery of valuable metals (Li, Co, Ni, and Mn) from the cathode material of waste lithium-ion batteries (LIBs), a mechanochemical reduction technique is proposed in this research. The cathode material was mechanochemically ball milled with various reductive agents as a pretreatment and then subjected to a chemical leaching process for the recovery of valuable metals. The influence of mechanochemical ball milling parameters and leaching conditions on metals recovery, and the changes in physicochemical properties of cathode materials before and after mechanochemical ball milling were investigated. The results show that Zinc (Zn) powder was an effective co-grinding reagent forimproving the recovery of valuable metals from cathode materials. The crystal structure of the cathode material gradually shifted to an amorphous state with an increase in ball milling speed and time. Mn(IV) and Co(III) in the cathode material were mechanochemically reduced to Mn(III) and Co(II) after co-grinding with Zn, which was beneficial to their leaching. The activation energies of Ni and Co decreased from 30.47 KJ/mol and 31.99 KJ/mol to 5.58 KJ/mol and 7.15 KJ/mol, respectively. The leaching rates of Li, Ni, Co, and Mn increased from 72.0%, 42.5%, 31.2%, and 15.2% to 99.9%, 96.2%, 94.3%, and 91.0% under the optimum conditions of a cathode material to Zn powder mass ratio of 7:3, a rotational speed of 500 rpm, a milling time of 2 h, and a ball-to-powder mass ratio of 19: 1. This research presents a highly efficient and feasible approach for recovering valuable metals from waste LIBs.