Synergistic Morphology and Electron Modulation Engineering Enables Cation–Anion Cointercalation and Conversion Chemistry

While bismuth chalcogenides have attracted considerable attention for their quantum topological states and spintronic application, there are few studies on bismuth chalcogenides in the field of ammonium-ion batteries (AIBs). Herein, a dual engineering strategy combines tungsten doping and morphological modulation to unlock Bi₂Te₃ for AIBs. Density functional theory calculations verify that W doping induces electron delocalization, and Bi vacancies create localized charge accumulation. The electronic recombination enables a reversible cation-anion coinsertion accompanied by a conversion reaction mechanism in W-Bi_2-<i>x</i>Te₃, which delivers 220 mAh g^-1 at 0.3 mA with exceptional cycling stability with over 2500 cycles at 3 A g^-1. The constructed aqueous "rocking-chair" AIB based on W-Bi_2-<i>x</i>Te₃//MnO₂ exhibits a large reversible capacity of 156.56 mAh g^-1 at 0.15 A g^-1 and a long lifespan of 2000 cycles. This work provides a facile electron engineering strategy on topological insulator as advanced anode for a new generation of AIBs.