Low-Temperature Molten-Salt-Assisted Recovery of Valuable Metals from Spent Lithium-Ion Batteries

A novel and environmentally friendly process for utilizing spent lithium-ion batteries based on salt roasting is proposed. The separated cathode material is roasted with NH₄Cl as a fluxing agent. During this process, Li and Co are converted to chlorides due to the release of HCl and NH₃ from the reaction of NH₄Cl, with LiCoO₂. These chloride salts are readily soluble in water. The reaction parameters, including roasting temperature, time, and LiCoO₂/NH₄Cl mass ratio, were investigated in detail. The results showed that more than 99% Co and Li were recovered under optimum conditions: temperature of 350 °C, reaction time of 20 min, and a LiCoO₂/NH₄Cl mass ratio of 1:2. A possible reaction mechanism between LiCoO₂ and NH₄Cl is proposed based on thermodynamic, X-ray diffraction, and X-ray photoelectron spectroscopy analyses. The treatment of other spent lithium-ion battery cathode materials, such as LiMn₂O₄ and LiCo_1/3Mn_1/3Ni_1/3O₂, verified the effectiveness of the method for recovering the valuable metals.