Z-Scheme g-C3N4/TiO2 heterojunction for a high energy density photo-assisted Li-O2 battery

A lithium-oxygen battery based on the formation of lithium oxide (Li2O) can theoretically achieve a high energy density through a four-electron reaction. This is more challenging to accomplish than the one- and two-electron reactions that produce lithium superoxide (LiO2) and lithium peroxide (Li2O2), respectively. A stable cathode with a sufficient supply of electrons and Li cations to form Li2O must be developed to achieve a four-electron reaction for a lithium-oxygen battery. Herein, by utilizing a composite 3D-printed cathode composed of a g-C3N4/TiO2 (gCNTO) heterostructure nanoparticle with high porosity and high conductivity, we were able to provide ample space and numerous active/catalytic sites during the reaction process. Our findings indicate that Li2O is the product of the photo-assisted lithium-oxygen battery. Under illumination, the battery can be rechargeable for over 1000 hours at 0.05 mA cm(-2) with a small polarization gap. The photocathode delivers an ultra-high discharge capacity of 29.7 mA h cm(-2) at 0.5 mA cm(-2), resulting in a specific energy of approximately 515.12 W h kg(cell)(-1). The performance is superior to the battery with Li2O2 as a discharge product in the dark. This study paves the way for the rapid development of high-energy-density photo-assisted Li-O-2 batteries.