Achieving a Quasi‐Solid‐State Conversion of Polysulfides via Building High Efficiency Heterostructure for Room Temperature Na–S Batteries

Abstract The practical application of room temperature sodium–sulfur (RT Na–S) batteries are prevented by the sulfur insulation, the severe shuttling effect of high‐order sodium polysulfides (Na 2 S n , 4 ≤ n ≤ 8), and the sluggish reaction kinetics. Therefore, designing an ideal host material to suppress the polysulfides shuttle process and accelerate the redox reactions of soluble NaPSs to Na 2 S 2 /Na 2 S is of paramount importance for RT Na–S batteries. Here, a quasi‐solid‐state transformation of NaPSs is realized by building high efficiency MoC‐W 2 C heterostructure in freestanding multichannel carbon nanofibers via electrospinning and calcination methods (MoC‐W 2 C‐MCNFs). The multichannel carbon nanofibers are interlinked micro‐mesoporous structures that can accommodate volume change of electrode materials and confine the entire redox process of NaPSs (restraining the polysulfides shuttle process). Meanwhile, the MoC‐W 2 C heterostructure with abundant heterointerfaces can facilitate electron/ion transport and accelerate conversion of NaPSs. Consequently, the S/MoC‐W 2 C‐MCNFs cathode delivers a high capacity of 640 mAh g −1 after 500 cycles at 0.2 A g −1 and an excellent reversible performance of 200 mAh g −1 after ultralong 3500 cycles at 4 A g −1 . What's more, the heterostructure catalytic mechanism (a quasi‐solid‐state transformation) is proposed and confirmed in carbonate electrolyte by combining experimentally and theoretically.