A tandem electrocatalyst with dense heterointerfaces enabling the stepwise conversion of polysulfide in lithium-sulfur batteries

The complicated sulfur phase transformation and diversity kinetics of lithium polysulfide intermediates hinder the practical applications of Li-S batteries. Herein, we report that Mo-Ni bimetal sulfide nanosheets with dense heterointerfaces and defects can decouple the complicated reactions into well-controlled multi-steps in tandem. Specifically, the MoS₂ in Mo-Ni tandem catalyst is more effective in catalyzing the phase transformation from Li₂S₈ to Li₂S₄, while NiS₂ delivers higher catalytic activity toward both the Li₂S₄ to Li₂S conversion and the Li₂S dissociation steps, as indicated by density functional theory calculations and comprehensive experiments. This integrated system tends to selectively propel the stepwise conversion of sulfur and thereby enhancing the battery performance. As a result, the sulfur loaded cathode delivers a high initial capacity of 1481 mAh g⁻¹ at 0.2 C, and a low capacity decay rate of 0.0236% per cycle over 1000 cycles at 2 C. This study demonstrates the feasibility of using tandem catalysis for regulating the smooth solid-liquid-solid multiphase transformation of polysulfides.