Development Of Novel Redox Mediator And Application Of Synchrotron Radiation In-situ HRXRD In Li-O₂ Batteries

Li-O2 batteries have attracted increasing attention for its high theoretical energy density,which is considered as the most hopeful next generation energy storage system and expected to be used in electric vehicles,field,military,water equipment and other applications.Li-O2 battery is composed of lithium anode,electrolyte and anode Compared with other kinds of Li-O2 batteries,the nonaqueous Li-O2 battery has the advantages of high charging platform and strong safety.However,the Li-O2 battery face the problems of high charging voltage and poor cycling life for its poor conductivity and insolubility.As one of the major challenges facing the Li-O2 batteries,finding ways to decompose Li2O2 at a low charging voltage is quite significant for improving the overall performance of these batteries.There are mainly two methods to develop solid catalyst and soluble redox mediator.Compared with all kinds of heterogeneous catalysts,dissolved redox mediators(RMs)are more mobile in an electrolyte,which results in its unique advantage of electronic conductionHere,we first report ruthenocene(Ruc)as a mobile redox mediator in Li-O2 batteries.Ruc in the electrolyte effectively reduces the charging potential and greatly increases the cycling life.The results of ex-situ scanning electron microscope(SEM),X-ray diffraction spectrum(XRD),X-ray photoelectron spectroscopy(XPS)confirm that less discharge product residue was accumulated after charge process.The stability of ruthenium as RM against lithium anode was studied by SEM and XPS characterizations.To verify the reaction mechanisms of the mediator,free energy of the possible reaction pathways based on DFT are providedAdditionally,the synchrotron radiation HRXRD technology is developed to operando studies in the Li-O2 batteries.We designed independently an in-situ device to ensure the unblocked optical path.In addition,the circuit and O2 atmosphere are needed during the battery tests.In addition,the reaction kinetics for a battery with Ruc as RM was studied by tracking the Li2O2 decomposition during charging process by operando synchrotron radiation HRXRD in at Shanghai Synchrotron Radiation Facility(SSRF)...