Stabilizing lithium superoxide formation in lithium-air batteries by Janus chalcogenide catalysts

Solid lithium peroxide (Li2O2) is the major discharge product in Li-air batteries. However, the electronically insulating nature of Li2O2 tends to affect the battery's performance such as the polarization gap and cyclability. On the other hand, lithium superoxide (LiO2), generated through a one-electron transfer process, offers greater electronic conductivity, lower charge transfer resistance, and thus reduced charge potential. Nevertheless, LiO2 long-term stabilization as a final product remains a significant challenge. In this study, we present the molybdenum (Mo)-based Janus chalcogenide family featuring asymmetric structures as a new generation of cathode catalysts for Li-air batteries. These catalysts demonstrate remarkable efficacy in stabilizing LiO2 discharge products, even under high current densities of 5000 mA/g (corresponding to 0.5 mA/cm2). Our density functional calculations provide an understanding of why the asymmetric Mo-Janus chalcogenides result in LiO2 formation whereas the symmetric Mo-dichalcogenides produce Li2O2 as the discharge product. These results pave the way to explore a new generation of advanced catalysts for superoxide-based Li-air batteries.