TUNING THE DISCHARGE PATHWAYS FOR HIGH-PERFORMANCE LI-O2 BATTERIES WITH LOW OVERPOTENTIALS

Abstract

Rechargeable lithium-oxygen (Li-O2) batteries possess the high theoretical energy density. However, the remarkably high charge overpotential due to the insulating discharge products of Li2O2 causes a low coulombic and energy efficiency, and thereby degrading the cycle life. In this thesis, we focus on controlling the discharge pathways to achieve low charge overpotentials for high-performance Li-O2 batteries. In chapter 3, thin-film Li2O2 was realized to obtain low charge overpotentials by designing Co3O4-surface-functionalized porous carbon nanotubes as an efficient cathode catalyst for Li–O2 batteries. In chapter 4, we propose a strategy to obtain low charge overpotentials with a superior cycling performance, where the ideal Li2O2 storage matrix, the high conductivity of amorphous discharge products of Li2O2, and the superior Li2O2/cathode contact interface can be simultaneously achieved. In chapter 5, we convert the discharge products of Li2O2 into the lithium thiosulfate by adding lithium polysulfides in aprotic electrolytes.