Satisfying Both Sides: Novel Low-Cost Soluble Redox Mediator Ethoxyquin For High Capacity And Low Overpotential Li-O-2 Batteries

Due to cathode passivation caused by the insulating discharged products and by-products, Li-O-2 batteries sustain some obstacles encompassing poor discharge capacity and high overpotential. Herein, we introduce 6-Ethoxy2,2,4-trimethylquinoline (EQ) as a bifunctional redox mediator into electrolyte and investigate its influence on the electrochemical performance of Li-O-2 batteries. Strikingly, the discharge process is promoted in the solution phase by the solvated Li+ with EQ, and the correlative capacity exhibits more than a 30-fold increase than pristine Li-O-2 battery at the current density of 3000 mA g(-1) carbon. DFT calculations further clarify the working mechanism of oxygen reduction reaction (ORR) induced by EQ. Furthermore, the surface electrostatic potential diagram shows that N and O atoms in EQ are electron-rich, which is prone to donate electrons to get its desirable oxidation state and effectively catalyze the oxidation of Li2O2, resulting in the extremely low charge plateau at 3.08 V and longtime stable cyclability (150 cycles at a current density of 500 mA g(-1) carbon with a fixed capacity of 1000 mAh g(-1) carbon).