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

Despite their potential for high capacity, lithium oxygen (Li–O₂) 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-O₂ 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–O₂ 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.