Template assisted lithium superoxide growth for lithium-oxygen batteries.

Developing batteries with energy densities comparable to internal combustion technology is essential for a worldwide transition to electrified transportation. Li-O 2 batteries are seen as the 'holy grail' of battery technologies since they have the highest theoretical energy density of all battery technologies. Current lithium-oxygen (Li-O 2 ) batteries suffer from large charge overpotentials related to the electronic resistivity of the insulating lithium peroxide (Li 2 O 2 ) discharge product. One potential solution is the formation and stabilization of a lithium superoxide (LiO 2 ) discharge intermediate that exhibits good electronic conductivity. However, LiO 2 is reported to be unstable at ambient temperature despite its favorable formation energy at -1.0 eV per atom. In this paper - based on our recent work on the development of cathode materials for aprotic lithium oxygen batteries including two intermetallic compounds, LiIr 3 and LiIr, that are found to form good template interfaces with LiO 2 - a simple goodness of fit R factor to gauge how well a template surface structure can support LiO 2 growth, is developed. The R factor is a quantitative measurement to calculate the geometric difference in the unit cells of specific Miller Index 2D planes of the template surface and LiO 2 . Using this as a guide, the R factors for LiIr 3 , LiIr, and La 2 NiO 4+ δ , are found to be good. This guide is attested by simple extension to other noble metal intermetallics with electrochemical cycling data including LiRh 3 , LiRh, and Li 2 Pd. Finally, the template concept is extended to main group elements and the R factors for LiO 2 (111) and Li 2 Ca suggest that Li 2 Ca is a possible candidate for the template assisted LiO 2 growth strategy.