Ultrahigh Rate and Ultralong Life Span Sodium Storage of FePS Enabled by the Space Confinement Effect of Layered Expanded Graphite.

Metal phosphorus trichalcogenides have been regarded as promising high-capacity anode materials for sodium-ion batteries (SIBs) owing to their high reversible capacity. Nevertheless, their practical application is plagued by poor diffusion kinetics and dramatic volume fluctuations during the charge-discharge process, resulting in no satisfactory rate and life span so far. Herein, we propose a space-confinement strategy to remarkably promote the cycling stability and rate capacity by embedding FePS particles in the interlayer of expanded graphite (EG), which are derived from transformation of graphite intercalation compounds. The layered EG not only greatly alleviates the volume fluctuations of FePS by the space confinement effect so as to maintain the stability of the electrode microstructure, but it also ensures rapid Na and electron transfer during cycling. When acting as an anode for SIBs, the hybrid electrode delivers a highly reversible capacity of 312.5 mAh g at an ultrahigh rate of 50 A g while retaining an ultralong life span of 1300 cycles with a retention of 82.4% at 10 A g. Moreover, the excellent performance of the assembled full battery indicates the practical application potential of FPS/EG.