Ingeniously Designed Yolk-Shell-Structured FeSe2@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 FeSe2 nanoparticles encapsulated in NC nanoboxes (termed FeSe2@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 FeSe2@NDC NBs deliver remarkable rate performance (374.9 mA h g(-1) at 10.0 A g(-1)) and long-cycling stability (403.3 mA h g(-1) over 2000 loops at 5.0 A g(-1)). When further coupled with a self-made Na3V2(PO4)(3)@C cathode in sodium-ion full cells, FeSe2@NDC NBs also exhibit considerably high and stable sodium-storage performance.

Automated summary

Transition metal selenides show promise as anodes for sodium-ion batteries due to their high conductivity and theoretical capacity, but face challenges such as volume expansion and sluggish dynamics. A study successfully fabricated nitrogen-doped carbon-coated FeSe2 nanoparticles in NC nanoboxes, improving the rate performance and long-cycling stability of the composite material. The FeSe2@NDC NBs also demonstrated remarkable sodium-storage performance when combined with a Na3V2(PO4)3@C cathode in full cells.