Ingeniously Designed Yolk-Shell-Structured FeSe@NDC Nanoboxes as an Excellent Long-Life and High-Rate Anode for Half/Full Na-Ion Batteries.

Thanks to their high conductivity and theoretical capacity, transition metal selenides have demanded significant research attention as prospective anodes for sodium-ion batteries. Nevertheless, their practical applications are hindered by finite cycle life and inferior rate performance because of large volume expansion, polyselenide dissolution, and sluggish dynamics. Herein, the nitrogen-doped carbon (NC)-coated FeSe nanoparticles encapsulated in NC nanoboxes (termed FeSe@NDC NBs) are fabricated through the facile thermal selenization of polydopamine-wrapped Prussian blue precursors. In this composite, the existing nitrogen-doped dual carbon layer improves the intrinsic conductivity and structural integrity, while the unique porous yolk-shell architecture significantly mitigates the volume swelling during the sodium/desodium process. Moreover, the derived Fe-N-C bonds can effectively capture polyselenide, as well as promote Na transportation and good reversible conversion reaction. As expected, the FeSe@NDC NBs deliver remarkable rate performance (374.9 mA h g at 10.0 A g) and long-cycling stability (403.3 mA h g over 2000 loops at 5.0 A g). When further coupled with a self-made NaV(PO)@C cathode in sodium-ion full cells, FeSe@NDC NBs also exhibit considerably high and stable sodium-storage performance.