Using highly concentrated chloride solutions to leach valuable metals from cathode-active materials in spent lithium-ion batteries

This study focused on the extraction of valuable metals from the cathode-active materials in spent lithium-ion batteries using a high-concentration chloride solution. The effects of the concentrations of ammonium chloride (NH4Cl), hydrochloric acid (HCl), and reductants such as hydrogen peroxide (H2O2) and urea (CO(NH2)2) on metal extraction and chlorine production were studied experimentally. The leaching mechanism was analyzed, and a leaching model was established. It was found that the addition of solid NH4Cl to an HCl solution significantly improved the metal extraction capability of the latter and reduced the formation of chlorine gas by 96.0% compared to that only using HCl. The activation energies for leaching Li, Ni, Co, and Mn were determined to be 30.4, 38.5, 30.6, and 38.2 kJ·mol−1, respectively. This study demonstrates an environmentally friendly method for recycling metal resources from cathode-active materials and furthers understanding of how NH4Cl inhibits chlorine production when leaching with mixed solutions of HCl and NH4Cl.