Tuning the nucleation and decomposition of Li2O2 by fluorine-doped carbon vesicles towards high performance Li-O2 batteries

Abstract

Li-O2 batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities. However, large over-potential in oxygen evolution reactions (OER) caused by the decomposition obstacles of Li2O2 seriously impedes its electrochemical performances. Herein, a novel N, O, S and F co-doping vesicular carbon was prepared by self-template pyrolysis method and used in Li-O2 battery to tune the nucleation and decomposition of Li2O2. The introduction of F in the carbon matrix with suitable content can regulate the adsorption of intermediates, through which the morphology of Li2O2 can be controlled to film, favorable to its decomposition in charge process. The cathode based on the optimized F doped carbon vesicle exhibits improved electrochemical performances including a low over-potential, large capacity and a long-term stability. Density functional theory (DFT) results show that F and C in C–F bond hasve a strong interaction to Li and O in Li2O2, respectively, which can enhance the transfer of electrons from Li2O2 to the carbon matrix to generate hole polaron and thus accelerate the delithiation and decomposition of Li2O2. This work provides a new sight into understanding the mechanism of nucleation and decomposition of Li2O2 for the development of high-performance Li-O2 batteries.