Revealing the electrolyte-enhancement effect of FeP/carbon nanosheets for superior sodium storage

Ether-based electrolytes are of exceptional benefit for forwarding conversion-type transition metal phosphides toward advanced sodium energy storage, but the rooted understanding of electrochemical enhancement is scarcely investigated. In this work, two-dimensional FeP-embedded carbon (FeP/C) hybrid nanosheets are rationally synthesized for probing the distinct sodium storage behaviors in different electrolytes. Compared to the ester-based counterpart, the ether-based electrolyte enables the FeP/C composite electrode to show a significant capacity increase from 363.5 to 516.6 mAh g-1 at 0.1 A g-1 over 150 cycling tests. Mechanistic analysis reveals that the particle refinement of FeP constantly generate extra active sites for more sodiation capacity. Additionally, it is identified that the electrode can be stabilized by forming a thin, uniform, and inorganic-rich solid electrolyte interface (SEI) layer induced by the ether-based electrolyte, retaining 94% of the initial capacity at 1 A g-1 after 800 cycles. This work can afford in-depth understanding and development of advanced conversion-type anode materials for sodium storage technologies.