Achieving superior sodium storage of FeSe2@NC composite via optimizing architecture

• Hierarchical 3D FeSe 2 @NC microcubes composites were fabricated as anode for sodium-ions batteries. • Different architectures and carbon contents were realized via regulating pyrolysis temperature. • Optimized architecture endows FeSe 2 @NC composite with enhanced electrochemical reaction dynamics. • Superior charge transfer and sodium-ions migration rates benefit to facilitate sodium storage performance. Sodium ion batteries (SIBs) have been regarded as the most promising next-generation energy storage devices due to the inexpensive cost and natural abundance of sodium metal salts. However, SIBs suffer severe limits resulted from the absence of suitable anode materials with desired sodium storage capability. In this work, we fabricate 3D hierarchical FeSe 2 @NC composites with distinguishing microcube architectures and carbon contents via controlling pyrolysis temperature using berlin green (FeFe(CN) 6 ) as a template. FeSe 2 @NC-400 (FS-400) presents enhanced sodium-ions migration speeds and charge transfer kinetics benefiting from the optimal architecture, overwhelming FeSe 2 @NC-300 (FS-300) and FeSe 2 @NC-500 (FS-500). Naturally, FS-400 also exhibits the highest reversible specific capacity (410.3 mAh g −1 after 200 cycles at 0.2 A g −1 ) as well as the most excellent rate performance and cycling lifespan (396.7 mAh g −1 after 1300 cycles at 2.0 A g −1 ) among them when served as anode for SIBs. The remarkable sodium storage capability of FS-400 makes it suitable anode material for SIBs.