Se Vacancy Activated Bi₂Se₃ Nanodots Encapsulated in Porous Carbon Nanofibers for Aqueous Zinc and Ammonium Ion Batteries

Abstract Bismuth‐based materials show great potential in aqueous batteries. But it is difficult to design a bifunctional bismuth‐based material for zinc and ammonium ion batteries (ZIBs and AIBs). Herein, a electrospinning method followed by a selenization strategy is used to design Bi₂Se₃ nanodots embedded in porous carbon nanofibers. Experimental studies coupled with theoretical calculations prove that the designs of nanodot and Se vacancy improve the transfer and storage of Zn²⁺ and NH₄⁺. Bi₂Se₃ nanodots are restricted to porous carbon nanofibers during cyclic test. An insertion‐type mechanism is revealed by ex situ characterizations. As a result, this well‐designed electrode (6 mg cm⁻²) offers high reversible capacities of 270 mA h g⁻¹ in ZIBs and 192 mA h g⁻¹ in AIBs at 0.05 A g⁻¹ and long‐term cycle life (60% capacity retention at 10 A g⁻¹ after 20 K cycles for ZIBs, 78% capacity retention at 2 A g⁻¹ after 9 K cycles for AIBs). Remarkably, it still displays satisfactory performances even at an ultrahigh mass loading of 18 mg cm⁻². Furthermore, Zn²⁺ and NH₄⁺ full cells offer high reversible capacities of 120 and 90 mA h g⁻¹ at 0.05 A g⁻¹ respectively. This work provides a reference for designing a bifunctional electrode.