Engineering CSFe Bond Confinement Effect to Stabilize Metallic-Phase Sulfide for High Power Density Sodium-Ion Batteries.

Metallic-phase iron sulfide (e.g., Fe S ) is a promising candidate for high power density sodium storage anode due to the inherent metal electronic conductivity and unhindered sodium-ion diffusion kinetics. Nevertheless, long-cycle stability can not be achieved simultaneously while designing a fast-charging Fe S -based anode. Herein, Fe S encapsulated in carbon-sulfur bonds doped hollow carbon fibers (NHCFs-S-Fe S ) is designed and synthesized for sodium-ion storage. The NHCFs-S-Fe S including metallic-phase Fe S embrace higher electron specific conductivity, electrochemical reversibility, and fast sodium-ion diffusion. Moreover, the carbonaceous fibers with polar CSFe bonds of NHCFs-S-Fe S exhibit a fixed confinement effect for electrochemical conversion intermediates contributing to long cycle life. In conclusion, combined with theoretical study and experimental analysis, the multinomial optimized NHCFs-S-Fe S is demonstrated to integrate a suitable structure for higher capacity, fast charging, and longer cycle life. The full cell shows a power density of 1639.6 W kg and an energy density of 204.5 Wh kg , respectively, over 120 long cycles of stability at 1.1 A g . The underlying mechanism of metal sulfide structure engineering is revealed by in-depth analysis, which provides constructive guidance for designing the next generation of durable high-power density sodium storage anodes.