Experimental process and kinetic behavior of carbothermal reduction of lithium cobaltate as a cathode for waste lithium batteries

Abstract

Lithium cobaltate as a cathode material has great recycling value in the recycling process of spent lithium-ion batteries, To promote the thermal reduction process of lithium cobaltate and recover high-value cobalt and lithium metals, we studied the process of lithium cobaltate reduction by carbon under different conditions and its thermal reaction kinetics. The effects of calcination temperature, raw material ratio, pelletizing pressure and holding time on the reduction rate of lithium cobaltate were investigated by controlling variables. The results showed that the optimum experimental conditions were as follows: mass ratio of carbon and lithium cobaltate was 1:1, pelletizing pressure was 45 MPa, calcination temperature was 800 °C, and calcination time was 6 h. Under these conditions, lithium cobaltate could be converted into cobalt and lithium carbonate, and the recovery rate of cobalt and lithium was 97% and 95%, respectively. A kinetic study on the carbothermal reduction reaction of LiCoO2 showed that the average activation energy of the carbothermal reaction of LiCoO2 under nitrogen protection was 280.6851 kJ/mol, and the mechanism model of the thermal decomposition reaction of LiCoO2 was controlled by chemicals, showing a deceleration curve. The corresponding process conforms to the threedimensional diffusion mechanism of the inverse Jander equation, which lays a theoretical foundation for the high-efficiency separation and recovery of LiCoO2 cathode material for waste lithium-ion batteries.