Structural and Electronic Properties of Small Stoichiometric (Li2O2)n Clusters and Relevance to Li–O2 Batteries

Stoichiometric (Li 2 O 2 ) n clusters ( n = 1–6) were systematically studied by density functional theory calculations with hybrid B3LYP functional. The most stable structures of these clusters are triplet except for the Li 2 O 2 monomer. In the Li 2 O 2 monomer, the closed shell singlet is strongly favored. There are superoxide-like characteristics in terms of bond lengths and spin in the stoichiometric peroxide lithium clusters, which may have implications for the formation and decomposition of peroxide lithium in Li–O 2 batteries. Furthermore, the growth process of the lowest energy structures of (Li 2 O 2 ) n clusters is “ring-like” ( n = 2) → “rectangle-like” ( n = 3,4) → “Y-like” ( n = 5) → “disc-like” ( n = 6) feature, this growth pattern is in good agreement with the experimental observation at the initial phase of discharge in the Li–O 2 battery. In addition, the values of energy gaps for the (Li 2 O 2 ) n clusters are much smaller than the band gap of bulk phase, and thus the (Li 2 O 2 ) n cluster can enhance the electron conductivity in the peroxide lithium. The frontier molecular orbitals analysis indicates that there are π * antibonding on the surface of (Li 2 O 2 ) n clusters, making their structures more stable. Finally, the PES of (Li 2 O 2 ) n clusters have been simulated, we hope that our simulated PES can be compared with future experimental data.