Molecular dynamics simulations and experimental verification of the interaction mechanism between Li and CO under vacuum

A vacuum carbothermal reduction method for extracting Li metal has several advantages, including a high recovery rate, low fabrication cost, and environmental friendliness. However, carbon is often present in the obtained condensate, which decreases the direct Li yield. In this study, we examine the interactions between Li vapor and CO by conducting a thermodynamic analysis, dynamic simulations, and experimental research under vacuum. The obtained thermodynamic analysis data reveal that Li and CO actively react at a pressure of 10 Pa. The structures and energies of the reactive species adsorbed on the top, face-centered cubic, and bridge sites of the Li surface are calculated and compared. The interactions of one and two CO molecules with the Li (100) surface involve only physical adsorption. During the interactions between three CO molecules and the Li (100) surface, the C atoms bond to each other to form a chain (CO)n structure. With the continuous extension of the simulation time, the C-O bonds in this structure break, while O and Li atoms form Li2O. The obtained C species exist in the form of elemental C, and the entire process represents a one-step reaction. The phase composition of the condensate is examined by X-Ray Diffractometer. It is found that the condensation of Li vapor and CO under vacuum produces Li2O and carbonaceous aggregates, which is consistent with the results of molecular dynamics simulations. The formation mechanism of Li2O in condensed Li vapor involves the formation of a carbon chain that drives the entire process.