Tuning the structure and morphology of Li2O2 by controlling the crystallinity of catalysts for Li-O2 batteries

Abstract

Large overpotential in oxygen reduction and evolution reactions is the intractable obstruction of Li-O2 batteries, causing inferior round-trip efficiency and diminished cycle life. Modulating the reaction mechanism of Li2O2 is of crucial importance for a high-performance Li-O2 battery. Herein, we report a composite of amorphous RuO2 nanoparticles decorated carbon nanotubes (A-RuO2@CNT) as an efficient catalyst for Li-O2 batteries. The amorphous catalyst contains abundant defects and vacancies as well as distorted atom arrangements, which provide sufficient active sites for reactions and enhance the affinity for LiO2 intermediates. As a result, the formation/decomposition mechanisms of Li2O2 are reasonably regulated. An amorphous film-like Li2O2 product forms and uniformly deposits on the surface of A-RuO2@CNT, thus achieving faster redox kinetics and smaller overpotential. When used in Li-O2 batteries, the amorphous catalyst affords remarkably decreased charge overpotential and enhanced cyclic stability, which is superior to its crystalline counterpart.