Controlling Reversible Expansion of Li2O2 Formation and Decomposition by Modifying Electrolyte in Li-O2 Batteries

Summary The aprotic lithium-oxygen (Li-O 2 ) 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 demonstrate an originally designed Ru(II) polypyridyl complex (RuPC) though which the reversible expansion of Li 2 O 2 formation and decomposition can be achieved in Li-O 2 batteries. Experimental and theoretical results revealed that the RuPC can not only expand the formation of Li 2 O 2 in electrolyte but also suppress the reactivity of LiO 2 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 Li 2 O 2 products can be decomposed reversibly with a low overpotential. Consequently, the RuPC-catalyzed Li-O 2 batteries exhibited a high discharge capacity, a low charge overpotential, and an ultralong cycle life. This work provides an alternative way of designing the soluble organic catalysts for metal-O 2 batteries.