Controlling to Expand Reversibly Li2O2-formation/decomposition by Modifying Electrolyte in Lithium-oxygen Batteries

Abstract

Aprotic lithium-oxygen (Li-O2) battery has attracted worldwide attention because of its ultrahigh theoretical energy density. However, its practical application is critically hindered by cathode passivation, large polarization and severe parasitic reactions. Here, we demonstrated a newly designed ruthenium (II) polypyridyl complex (RuPC) by which an expanded reversibly Li2O2-formation/decomposition could be achieved in lithiumoxygen batteries. Experimental and theoretical results revealed that the RuPC can not only expand the formation of Li2O2 in electrolyte, but also suppress the reactivity of LiO2 intermediate during discharge, thus alleviating the cathode passivation and parasitic reactions significantly. In addition, an initial delithiation pathway can be achieved when charging in turn, thus the Li2O2 products can be decomposed reversibly with a low overpotential. As a result, the RuPC-catalyzed Li-O2 batteries exhibited a high discharge capacity (~9281 mAh g-1), a low charge overpotential (0.54 V) and a ultralong cycle life (371 cycles). This work provides an alternative way of designing the soluble organic catalysts for metal-oxygen batteries.