Oxygen defect-ridden molybdenum oxide-coated carbon catalysts for Li-O2 battery cathodes

Abstract

The aprotic Li-O2 batteries with high theoretical energy density hold great promise for long-range electric vehicles and grid energy storage system. However, the high over-potential, poor cycling stability and the side reactions associated with the carbon electrocatalysts at the cathode limit the practical application of Li-O2 batteries. To address these challenges, in this work, oxygen defect-ridden molybdenum oxide (MoOx) was coated on the surface of carbon nanotubes (CNTs) (denoted as MoOx/CNT) by a facile solvothermal reaction for the first time. This MoOx layer not only protects the CNTs catalysts from the side reactions but also promotes the reversible formation of Li2O2, resulting in low overpotential and excellent cycling stability of MoOx/CNT cathode. A charging overpotential of only about 0.52 V and an enhanced stability of more than 210 cycles are obtained for the as-prepared MoOx-coated CNT cathode. First-principles study by density functional theory (DFT) reveals that the stabilization of LiO2 intermediates is enabled on oxygen-defected MoOx during discharge process, leading to the formation of large sheet-like Li2O2 crystallites that are easy to be decomposed during charge process. This makes a crucial contribution to the enhanced electrochemical performance of MoOx/CNT cathode.