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 Bi2Se3 with acceptable Bi-vacancies for ZIBs cathode (Cu-Bi2−xSe3) is constructed through one-step hydrothermal process accompanied by Cu heteroatom introduction. The cation-deficient Cu-Bi2−xSe3 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−xSe3. Therefore, Cu-Bi2−xSe3 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−xSe3 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−xSe3 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.