title: Stability of lithium superoxide LiO2 in the gas phase: computational study of dimerization and disproportionation reactions.
abstract: Knowledge of the precise molecular mechanisms during the discharge and recharge processes in the lithium-air battery is critical for achieving desired improvements in specific capacity, current density, and cyclability. The initial oxygen reduction product formed in the presence of Li(+) ions is lithium superoxide LiO(2). In this study, we report the computed structures and thermodynamic parameters of LiO(2) dimerization in the gas phase, which enables us to provide a baseline for the reaction free energy profile of the subsequent disproportionation of (LiO(2))(2) to lithium peroxide Li(2)O(2) and O(2). Our calculations identified several low-lying (LiO(2))(2) dimers, with the singlet bipyramidal structure giving IR bands that are consistent with the characteristic IR vibration frequencies of (LiO(2))(2) in the oxygen matrix at T = 15-40 K. The activation barrier for (LiO(2))(2) = Li(2)O(2)+O(2) is 10.9 kcal/mol at the UCCSD(T)/CBS level (T = 298 K), suggesting that in the gas phase LiO(2) and its aggregates could only be observed at low temperatures.
authors.affiliation: Liox Power, Incorporated, 129 North Hill Avenue, Suite 103, Pasadena, California 91106, USA. slava@liox.com
authors.forename: Vyacheslav S
authors.initials: VS
authors.lastname: Bryantsev
authors.forename: Mario
authors.initials: M
authors.lastname: Blanco
authors.forename: Francesco
authors.initials: F
authors.lastname: Faglioni