Thermal decomposition kinetics of basic carbonate cobalt nanosheets obtained from spent Li-ion batteries: Deconvolution of overlapping complex reactions

A new non-isothermal method of kinetic analysis was employed to investigate the thermal decomposition kinetic modeling of the basic carbonate cobalt nanosheets (n-BCoC) synthesized from spent lithium-ion batteries (LIBs). Fraser–Suzuki function was applied to deconvoluting overlapping complex processes from the overall differential thermal curves obtained under the linear heating rate conditions, followed by the kinetic analysis of the discrete processes using a new kinetic analysis method. Results showed that the decomposition of n-BCoC in air occurred through two consecutive reactions in the 136–270 °C temperature intervals. Decomposition started by hydroxide component (Co(OH)₂) decomposition until to 65% and simultaneously carbonate phase decarbonation began. The process was continued by CO₂ evolution and finally carbonate cobalt nanosheets have been produced. The reaction mechanism of the whole process can be kinetically characterized by two successive reactions: a phase boundary contracting reaction followed by an Avrami–Erofeev equation. Mechanistic information obtained by the kinetic study was in good agreement with FT-IR (Fourier transform infrared spectroscopy) and SEM (scanning electron microscopy) results.