In-situ fabrication of active interfaces towards FeSe as advanced performance anode for sodium-ion batteries.

Transition metal selenides have gained enormous interest as anodes for sodium ion batteries (SIBs). Nonetheless, their large volume expansion causing poor rate and inferior cycle stability during Na insertion/extraction process hinders their further applications in SIBs. Herein, a confined-regulated interfacial engineering strategy towards the synthesis of FeSe microparticles coated by ultrathin nitrogen-doped carbon (NC) is demonstrated (FeSe@NC). The strong interfacial interaction between FeSeand NC endows FeSe@NC with fast electron/Na transport kinetics and outstanding structural stability, delivering unexceptionable rate capability (364 mAh/gat 10 A/g) and preeminent cycling durability (capacity retention of 100 % at 1 A/g over 1000 cycles). Furthermore, variousex situcharacterization techniques and density functional theory (DFT) calculations have been applied to demonstrate the Na storage mechanism of FeSe@NC. The assembled NaV(PO)F@rGO//FeSe@NC full cell also displays a high capacity of 241 mAh/gat 1 A/g with the capacity retention of nearly 100 % over 2000 cycles, and delivers a supreme energy density of 135 Wh kg and a topmost power density of 495 W kg, manifesting the latent applications of FeSe@NC in the fast charging SIBs.