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

FeSe microparticles coated by ultrathin nitrogen-doped carbon (FeSe@NC) have been synthesized through the dopamine coating of FeOOH precursor and the post-calcination treatment. The strong interfacial interaction between FeSe and NC guarantees FeSe@NC with fast electron/Na+ transport kinetics and outstanding structural stability. [Display omitted] • FeSe@NC exhibits preeminent performance as an anode for sodium-ion batteries. • Analyses of ex-situ XRD, ex-situ TEM and DFT calculations reveal that the electrochemical mechanism in FeSe. • Excellent performance is related to a reversible phase transformation from hexagonal to tetragonal. • NVPF@rGO//FeSe@NC full battery maintains a capacity of 241 mAh/g after 2000 cycles at 1 A/g. 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 FeSe and NC endows FeSe@NC with fast electron/Na+ transport kinetics and outstanding structural stability, delivering unexceptionable rate capability (364 mAh/g at 10 A/g) and preeminent cycling durability (capacity retention of 100 % at 1 A/g over 1000 cycles). Furthermore, various ex situ characterization techniques and density functional theory (DFT) calculations have been applied to demonstrate the Na+ storage mechanism of FeSe@NC. The assembled Na 3 V 2 (PO 4) 2 F 3 @rGO//FeSe@NC full cell also displays a high capacity of 241 mAh/g at 1 A/g with the capacity retention of nearly 100 % over 2000 cycles, and delivers a supreme energy density of 135 Wh kg−1 and a topmost power density of 495 W kg−1, manifesting the latent applications of FeSe@NC in the fast charging SIBs. [ABSTRACT FROM AUTHOR]