Electrocatalysis of polysulfide conversion by conductive RuO2 nano dots for lithium-sulfur batteriesElectronic supplementary information (ESI) available. See DOI: 10.1039/c8nr04182b

The practical use of the rechargeable lithium-sulfur (Li-S) battery is still restricted by poor cycle life and rate performance caused by the shuttle of soluble redox intermediates and low conductivity of S/Li 2 S. A comprehensive approach is to tune the multi-electron redox reactions and construct reversible chemical bonds with polysulfide intermediates. In this study, RuO 2 nano dots (NDs) are proposed to anchor polysulfides, trigger the surface-mediated reduction of polysulfides and to facilitate the formation of Li 2 S 2 /Li 2 S through its catalytic effect for the first time. When serving as the sulfur host, the RuO 2 NDs can retard the shuttle of polysulfides, accelerate the redox reaction of polysulfides, and therefore result in improved sulfur utilization and enhanced rate performance. The designed RuO 2 @NMCs/S ternary electrodes with high sulfur loading of 70 wt% could achieve a low decay rate of 0.07% per cycle for 500 cycles at a 0.5 C-rate. Realized by fast electrode kinetics, the reversible capacity of 634 mA h g −1 is attained at a high C-rate of 5 C. Overall, this strategy sheds new light on the oxide mediators for reversible modulation of electrochemical reactions in lithium-sulfur (Li-S) batteries. Highly conductive RuO 2 nano dots (NDs) are taken as an efficient anchor and catalytic conversion center of polysulfides for the first time, the designed RuO 2 @NMCs/S ternary electrodes possess superior rate capability and ultra-long cycle life.