Metal-organic frameworks engaged formation of FeSe2/N-doped carbon as anode enables high-performance sodium-ion batteries.

• N-doped carbon encapsulated FeSe 2 (FeSe 2 @NC) has prepared for sodium-ion batteries. • The carbon layer improves electronic conductivity and alleviates volume expansion. • FeSe 2 @NC exhibits superior pseudocapacitance contribution and Na-ion storage. • Sodium-ion capacitors were assembled using FeSe 2 @NC anode and AC cathode. Sodium-ion batteries (SIBs) have great potential for large-scale energy storage, whereas the development of satisfactory anode material is still a challenge. Herein, the nitrogen-doped carbon encapsulated FeSe 2 (FeSe 2 @NC) with spindle-like nanostructures are proposed by polymerization, carbonization and selenization strategies. The N-doped carbon layer effectively improves the electronic conductivity, provides more activity sites, and alleviates the volume expansion. As expected, the prepared FeSe 2 @NC delivers excellent rate performance (232.3 mAhg−1 at 1.0 Ag−1) and superior cycle stability (269.8 mAhg−1 after 500 cycles). Significantly, this work proposes an effective material engineering approach for designing transition metal selenides for high-performance SIBs. [ABSTRACT FROM AUTHOR]