Spent lithium–ion battery recycling: Thermodynamic, phase transition, and kinetic analysis of carbon thermal reduction of Al-containing NCM cathode materials

The carbon thermal reduction process is considered an industrially promising method for spent ternary cathode materials. It’s comprehensive studies to address the reduction thermodynamics, phase transition, and kinetic behaviours of actual Al-containing ternary materials has received increasing attention. In this study, based on thermodynamic evaluation, under ideal conditions, both C and Al are suitable reducing agents. And the reduction difficulty is Mn > Co > Ni from thermodynamic and experimental analysis. The predicted products are mainly Ni, Co, CoO, NiO, MnO, Li 2 CO 3 , and Li-Al compounds. Further, phase transition analysis indicates that it is feasible to reduce the material while simultaneously suppressing Li-Al bonding, with composition of Ni or Co, Li 2 CO 3 , and MnO, by controlling the conditions of 700 °C for 2 h with 15% carbon. According to thermogravimetric analysis, this process can be roughly divided into three stages, including evaporation, decomposition and reduction, respectively. Finally, the results of kinetics analysis combining the Coats-Redfern and KAS/FWO models indicates that the corresponding activation energy increases from 13.46 kJ/mol to 481.53 kJ/mol across the reaction stages. This study may provide theoretical foundations for practical recycling of Al-containing battery materials, and demonstrate the broad prospects of the carbon thermal reduction process for industrial application.