Adsorption mechanisms of lithium oxides (Li_xO₂) on a graphene-based electrode: A density functional theory approach

Highlights: • Lithium oxide (Li_xO₂) adsorption mechanisms onto a graphene-based electrode. • The adsorption energy of LiO₂ on graphene (−0.450 eV). • Li₂O₂ revealed that the parallel configurations (−0.630 to −0.611 eV) were more stable. • The energy bands in the Li₂O₂@graphene system were shifted down. - Abstract: We computationally modeled the adsorptive behavior of O₂, Li, LiO₂, and Li₂O₂ on graphene using density functional theory (DFT) in an effort to understand the mechanisms by which lithium oxides (Li_xO₂) and oxygen reduction reaction (ORR) products adsorb onto graphene-based electrodes during lithium–air battery operation. O₂ weakly adsorbed onto graphene with a binding energy of −0.111 to −0.089 eV, whereas Li strongly adsorbed onto graphene with relatively large binding energy of −1.079 to −0.774 eV. The LiO₂ formation energy (−2.453 eV) was much lower than the LiO₂ adsorption energy (−0.450 eV) on graphene, indicating that after Li and O₂ had associated, LiO₂ adsorbed onto the graphene surface. Among the various Li₂O₂ adsorption configurations, the parallel configurations in which Li₂O₂ was oriented along the graphene axis (−0.630 to −0.611 eV) were more favorable than the perpendicular configurations (−0.513 to −0.475 eV). Consequently, more charges were transferred from Li to graphene in a parallel orientation