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

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.