Lithium Superoxide in Li-O2 Batteries: Performance and Mechanisms

Abstract

Lithium superoxide (LiO2) is generally regarded as an intermediate formed during the Li-O2 battery discharge and transformed into lithium peroxide (Li2O2). Indeed, its chemical/electrochemical stability is low, making it recognized as a temporary discharge product in Li-O2 battery chemistry. However, in 2016, utilizing an iridium (Ir)-based electrocatalyst, Curtiss and Amine et al. found that LiO2 can be epitaxially grown on the surface of Ir catalyst and can be stable under cycling conditions.1 In the study, a templating mechanism was suggested, where a good lattice matching of LiIr3 surfaces (formed on the Ir catalyst) with that of LiO2 facilitates LiO2 formation as a singular discharge product. Following studies showed some superior electrochemical properties of LiO2 in comparison to Li2O2, including lower charge overpotentials. Meanwhile, some other transition metal compounds have recently exhibited LiO2 formation, where the formation mechanism suggested may not be a templating method. In this case, there could be strong adsorption of LiO2 in specific structures, resulting in suppressed Li2O2 generation. Herein, we will present experimental and computational results on some new catalysts for LiO2 formation and discuss possible underlying mechanisms.AcnowledgementThis work was primarily supported by the US Department of Energy under contract DE-AC02-06CH11357 from the Vehicle Technologies Office, Department of Energy, Office of Energy Efficiency and Renewable Energy.Reference1 Curtiss. L. and Amine. K. et al. A lithium–oxygen battery based on lithium superoxide. Nature 2016, 529, 377-382