Lithium Superoxide in Li-O₂ Batteries: Performance and Mechanisms

Lithium superoxide (LiO 2 ) is generally regarded as an intermediate formed during the Li-O 2 battery discharge and transformed into lithium peroxide (Li 2 O 2 ). Indeed, its chemical/electrochemical stability is low, making it recognized as a temporary discharge product in Li-O 2 battery chemistry. However, in 2016, utilizing an iridium (Ir)-based electrocatalyst, Curtiss and Amine et al. found that LiO 2 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 LiIr 3 surfaces (formed on the Ir catalyst) with that of LiO 2 facilitates LiO 2 formation as a singular discharge product. Following studies showed some superior electrochemical properties of LiO 2 in comparison to Li 2 O 2 , including lower charge overpotentials. Meanwhile, some other transition metal compounds have recently exhibited LiO 2 formation, where the formation mechanism suggested may not be a templating method. In this case, there could be strong adsorption of LiO 2 in specific structures, resulting in suppressed Li 2 O 2 generation. Herein, we will present experimental and computational results on some new catalysts for LiO 2 formation and discuss possible underlying mechanisms. Acnowledgement This 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. Reference 1 Curtiss. L. and Amine. K. et al. A lithium–oxygen battery based on lithium superoxide. Nature 2016, 529 , 377-382