RuO2-coated MoS2 Nanosheets as Cathode Catalysts for High Efficiency Li-O2 Batteries

Despite their potential for high capacity, lithium oxygen (Li-O-2) batteries still suffer from the low round-trip energy efficiency and limited cycle life, mainly due to the slow decomposition of discharge products. Therefore, developing efficient catalysts is a key issue for the practical application of Li-O-2 batteries. Ruthenium oxide (RuO2) is one of the most efficient catalysts developed thus far for lithium-air batteries. However, the high price and limited availability of Ru prohibits its large-scale use in practical device fabrications. Recently, molybdenum disulfide (MoS2) has been actively investigated in various catalytic systems, taking advantage of its two-dimensional (2D) structure and catalytic activities. However, the low electrical conductivity of MoS2 limits the realization of fully operative MoS2-based catalysts on its own. In this report, RuO2-coated MoS2 nanosheets (RuO2/MoS2) are prepared and implemented as cathode catalysts for Li-O-2 batteries. In this hybrid structure, RuO2 and MoS2 complement each other; the poor electrical conductivity of MoS2 is overcome by the nearly conformal coating of conducting RuO2, while 2D MoS2 nanosheets act as excellent supports for RuO2 catalysts and also contribute to the overall catalytic activities. These combined features result in excellent cathode performance, including improved efficiency and cycling lifetimes, with significantly reduced amounts of precious RuO2.