imaging of lithium superoxide dynamics in an all-solid-state Li-O nanobattery

Lithium superoxide (LiO 2 ), which is considered to be an unstable intermediate, was shown recently to be a stable discharge product in lithium oxygen batteries (LOBs). As such, the in situ observation of LiO 2 dynamics may provide direct evidence for the working mechanism of LOBs. Here we report in situ imaging of the nucleation, growth and stabilization of LiO 2 in LOBs with Au nanoparticle coated carbon nanotubes as an air cathode by aberration corrected environmental transmission electron microscopy. During discharge, LiO 2 spheres nucleated and grew from aggregated Li-Au alloy (Li 15 Au 4 ) nanoparticle seeds and were stable for several minutes. Density functional theory calculations suggest that the de-activation of lithium via electron transfer from Li to Au and O weakens Li's electron donation capability and prevents the dissolution of superoxide-like species, which favors a one electron transfer oxygen reduction reaction, thus facilitating the nucleation and stabilization of LiO 2 . The lithium de-activation induced LiO 2 dynamics advances our understanding of LiO 2 mediated solid-state LOBs and may provide a new strategy for the design of LOBs. In situ imaging of LiO 2 dynamics in LOBs with Au/CNT cathode was conducted by ETEM. During discharge, LiO 2 formed from Li 15 Au 4 seeds with stability for several minutes. The de-activation of Lifacilitates the nucleation and stabilization of LiO 2 .