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 Bi 2 Se 3 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 Zn 2+ and NH 4 + . Bi 2 Se 3 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, Zn 2+ and NH 4 + 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.