Air activation enhances the porosity and N,O synergistic effect towards an efficient metal free carbon cathode for Li-O2 battery

Abstract

The achievement of Li-O2 batteries with high energy density and extended cycle life is often hindered by the disorderly growth of solid discharge product Li2O2 on the cathode and its sluggish decomposition reaction kinetics. Herein, under the guidance of DFT simulations, the N,O co-doped carbon was identified as a potential efficient metal free cathode catalyst to remit these problem in Li-O2 batteries. Then, a spherical shell-like N,O co-doped carbon was prepared through the direct pyrolysis of guanosine 5′-monophosphate disodium salt (5′-GMP, 2Na). After a further activation process in air, the carbon shells exhibit a finer porous surface with greatly enhanced specific surface area and surface N,O contents. As a result, the morphology of Li2O2 changed from large toroidal to film by using the activated carbon as a cathode catalyst due to its tailored surface structure with improved N and O synergistic effect. What's more, the film-like Li2O2 with Li vacancy can not only form an increased interfacial contact and interaction with the active sites on carbon, but also be conducive to the transfer of Li+/electrons during the decomposition of Li2O2, thus accelerating the electrochemical performances of the battery.