Thermodynamic and kinetic analysis for carbothermal reduction process of CoSb alloy powders used as anode for lithium ion batteries

Thermodynamic calculation and kinetic analysis were performed on the carbothermal reduction process of Co3O4–Sb2O3–C system to clarify the reaction mechanism and synthesize pure CoSb powder for the anode material of secondary lithium-ion batteries. The addition of carbon amount and thus the purity of CoSb powders were critical to the electrochemical property of CoSb anode. It was revealed that in an inert atmosphere, Co3O4 was preferentially reduced to CoO, followed by the reduction of Sb2O3 and CoO. CO2 was the gas product for the reduction of Co3O4 and Sb2O3, while CO was the gas product for that of CoO. Based on the analysis result, pure CoSb powder without any oxides and residual carbon was synthesized, which showed a higher specific capacity and a lower initial irreversible capacity loss, compared to CoSb sample with residual carbon. This work can be a reference for other carbothermal reduction systems.

► Carbothermal reduction mechanism of Co4O3–Sb2O3–C system was clarified based on thermodynamic calculation and kinetic analysis.
► Actually required carbon amount for carbothermal reduction process was suggested.
► Pure CoSb powder was prepared via carbothermal reduction process, which shows high electrochemical performance as anode for lithium ion battery.