Computational Insights into LiO Formation, Nucleation, and Adsorption on Carbon Nanotube Electrodes in Nonaqueous Li-O Batteries.

Recent theoretical and experimental studies have shown that the formation of LiO, the main discharge product of nonaqueous Li-O batteries, is a complex multistep reaction process. The formation, nucleation, and adsorption of LiO ( and = 0, 1, and 2) and (LiO) clusters with = 1-4 on the surface of carbon nanotubes (CNTs) were investigated by periodic density functional theory calculation. The results showed that both LiO and LiO on CNT electrodes are preferentially generated by lithiation reaction rather than disproportionation reaction. The free energy profiles demonstrate that the discharge potentials of 2.54 and 1.29 V are the threshold values of spontaneous nucleation of (LiO) and (LiO) on a CNT surface, respectively. The electronic structure indicates that LiO is a -type semiconductor, while LiO exhibits the properties of an insulator. Interestingly, once LiO molecules condense into large clusters, they will be repelled away from the CNT surface and continue to grow into large-sized LiO. Our results provide insights into the full understanding of the electrochemical reaction mechanism and product formation processes of lithium oxides in the cathodes of Li-O batteries.