Internal Electric Field and Interfacial Bonding Engineered Step-Scheme Junction for a Visible-Light-Involved Lithium-Oxygen Battery.

Abstract

Li-O2 batteries have aroused considerable interest in recent years, however they are hindered by high kinetic barriers and large overvoltages at cathodes. Herein, a step-scheme (S-scheme) junction with hematite on carbon nitride (Fe2 O3 /C3 N4 ) is designed as a bifunctional catalyst to facilitate oxygen redox for a visible-light-involved Li-O2 battery. The internal electric field and interfacial Fe-N bonding in the heterojunction boost the separation and directional migration of photo-carriers to establish spatially isolated redox centers, at which the photoelectrons on C3 N4 and holes on Fe2 O3 remarkably accelerate the discharge and charge kinetics. These enable the Li-O2 battery with Fe2 O3 /C3 N4 to present an elevated discharge voltage of 3.13 V under illumination, higher than the equilibrium potential 2.96 V in the dark, and a charge voltage of 3.19 V, as well as superior rate capability and cycling stability. This work will shed light on rational cathode design for metal-O2 batteries.