Recovery of Cobalt and Lithium by Carbothermic Reduction of LiCoO2 Cathode Material: A Kinetic Study

Abstract

Recycling of Li-ion battery cathode materials using carbon from the anode materials via carbothermic reduction would provide a reduction process option that could be carried out without introducing any external reactants. From this basis, this study investigated and examined the kinetics of carbothermic reduction of LiCoO2 at 700 °C to 1100 °C under inert atmosphere up to 240 minutes reaction time using an isothermal mass change analysis combined with detailed microstructure evolution observation. The overall reduction mechanism appeared to involve diffusion of oxygen in LiCoO2 during its thermal decomposition in the first stage, followed by the nucleation of cobalt in the second stage. The activation energy of the diffusion and nucleation stages were calculated to be 121 and 95 kJ/mol, respectively. The microstructure analyses showed a complex evolution of phases. At 700 °C to 900 °C, Li2CO3 and Co phases were observed as the product of the reductions; while at 1000 °C to 1100 °C, Li2O and Co phases were observed. The information and data obtained are useful when comparing different recycling methods and optimizing the carbothermic reduction parameters for recycling cathode materials from spent Li-ion batteries.