In situ reduction of cathode material by organics and anode graphite without additive to recycle spent electric vehicle LiMn2O4 batteries

In a conventional roasting-sorting process to obtain cathode powders, the phase structure of LiMn2O4 is not dissociated and the valence of manganese is not changed, resulting in low metal recovery efficiency and high reagent cost in the subsequent leaching process. In this context, a novel process is developed to realize the recovery of spent LiMn2O4 lithium-ion batteries (LIBs) via one-step pyrolysis and reductant-free acid leaching. The leaching efficiencies of lithium and manganese are respectively 99.9% and 99.4% under the optimal pyrolysis conditions: a temperature of 500 °C, a nitrogen flow rate of 50 mL/min, and a pyrolysis time of 60 min. The analysis of thermogravimetry-infrared spectroscopy indicates volatilization of electrolyte and decomposition of LiPF6 occur in the temperature range of 100–180 °C. When the temperature rises from 180 to 800 °C, high molecular weight polymers (binder and separator) are degraded into pyrolytic gas and oil. LiMn2O4 is deconstructed and reduced to MnO and Li2CO3 under the synergistic effect of pyrolytic gas and anode graphite. The harmful fluorine and phosphorus are absorbed by Ca(OH)2 solution to avoid environmental hazards. The results suggest that the process integrated pyrolysis and aicd leaching is efficient, environmental-friendly, and low-cost for recycling spent LiMn2O4 LIBs.