Cation Defect‐Engineered Boost Fast Kinetics of Two‐Dimensional Topological Bi₂Se₃ Cathode for High‐Performance Aqueous Zn‐Ion Batteries

The challenge with aqueous zinc-ion batteries (ZIBs) lies in finding suitable cathode materials that can provide high capacity and fast kinetics. Herein, two-dimensional topological Bi₂ Se₃ with acceptable Bi-vacancies for ZIBs cathode (Cu-Bi2-x Se₃ ) is constructed through one-step hydrothermal process accompanied by Cu heteroatom introduction. The cation-deficient Cu-Bi2-x Se₃ nanosheets (≈4 nm) bring improved conductivity from large surface topological metal states contribution and enhanced bulk conductivity. Besides, the increased adsorption energy and reduced Zn²⁺ migration barrier demonstrated by density-functional theory (DFT) calculations illustrate the decreased Coulombic ion-lattice repulsion of Cu-Bi2-x Se₃ . Therefore, Cu-Bi2-x Se₃ exhibits both enhanced ion and electron transport capability, leading to more carrier reversible insertion proved by in situ synchrotron X-ray diffraction (SXRD). These features endow Cu-Bi2-x Se₃ with sufficient specific capacity (320 mA h g⁻¹ at 0.1 A g⁻¹ ), high-rate performance (97 mA h g⁻¹ at 10 A g⁻¹ ), and reliable cycling stability (70 mA h g⁻¹ at 10 A g⁻¹ after 4000 cycles). Furthermore, quasi-solid-state fiber-shaped ZIBs employing the Cu-Bi2-x Se₃ cathode demonstrate respectable performance and superior flexibility even under high mass loading. This work implements a conceptually innovative strategy represented by cation defect design in topological insulator cathode for achieving high-performance battery electrochemistry.