Recycling of valuable metals from spent lithium-ion batteries by self-supplied reductant roasting

The massive spent lithium-ion batteries (LIBs) need to be recycled due to their increasing decommission in recent years. This paper aims to propose an effective process that uses self-supplied reductant roasting and acid leaching to recover Lithium, Nickle, Cobalt and Manganese from spent LIBs. In the absence of external carbon resources, the waste membrane from spent LIBs was used as the reductant in the self-supplied reductant roasting. A thermodynamic analysis was conducted to judge the possible reduction reaction between the cathode material and waste membrane. Then, the effects of roasting temperature, roasting time and membrane dosage on the crystal structure and phase transformation of roasting products were investigated and optimized. After the roasting process, the valence state of metals in the cathode material decreased and the structure became loose and porous. Moreover, the layer structure of the cathode material was transformed into groups of Li2CO3, Ni, Co, NiO, CoO and MnO. Further, the reduction effect of cathode powders under each roasting condition was verified under the same leaching conditions. After leaching for 30 min, the leaching efficiencies of Li, Ni, Co and Mn were over 99% under the optimum roasting conditions. Finally, economic assessments proved that the proposed process is profitable. The whole process demonstrates an effective and positive way for recycling spent LIBs and making full use of their waste membrane, which promotes resource recovery and environmental protection.