Ultrafast and ultrastable FeSeembedded in nitrogen-doped carbon nanofibers anode for sodium-ion half/full batteries.

Transition metal selenides are considered as promising anode materials for fast-charging sodium-ion batteries due to their high theoretical specific capacity. However, the low intrinsic conductivity, particle aggregation, and large volume expansion problems can severely inhibit the high-rate and long-cycle performance of the electrode. Herein, FeSenanoparticles embedded in nitrogen-doped carbon nanofibers (FeSe@NCF) have been synthesized using the electrospinning and selenization process, which can alleviate the volume expansion and particle aggregation during the sodiation/desodiation and improve the electrical conductivity of the electrode. The FeSe@NCF electrode delivers the outstanding specific capacity of 222.3 mAh gat a fast current density of 50 A gand 262.1 mAh gat 10 A gwith the 87.8% capacity retention after 5000 cycles. Furthermore, the Na-ion full cells assembled with pre-sodiated FeSe@NCF as anode and NaV(PO)/C as cathode exhibit the reversible specific capacity of 117.6 mAh gat 5 A gwith the 84.3% capacity retention after 1000 cycles. This work provides a promising way for the conversion-based metal selenides for the applications as fast-charging sodium-ion battery anode.