Atomically Dispersed Dual-Site Cathode with a Record High Sulfur Mass Loading for High-Performance Room-Temperature Sodium-Sulfur Batteries

Room-temperature sodium-sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS2 and Mo-1 (S@MoS2-Mo-1/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS2-Mo-1/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g(-1) at 0.1 A g(-1) and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.

Automated summary

Room-temperature sodium-sulfur batteries have high potential for energy storage, but issues like low S mass loading and poor cycling stability limit their capacity. This study successfully synthesized sulfur-doped graphene frameworks supporting 2H-MoS2 and Mo-1, leading to a cathode with record-high sulfur mass loading and excellent cycling stability. Experimental and computational results revealed the enhancement mechanisms.