Cation Defect-Engineered Boost Fast Kinetics of Two-Dimensional Topological Bi 2 Se 3 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 Bi ₂ Se ₃ with acceptable Bi-vacancies for ZIBs cathode (Cu-Bi _2-x Se ₃ ) is constructed through one-step hydrothermal process accompanied by Cu heteroatom introduction. The cation-deficient Cu-Bi _2-x Se ₃ nanosheets (≈4 nm) bring improved conductivity from large surface topological metal states contribution and enhanced bulk conductivity. Besides, the increased adsorption energy and reduced Zn ²⁺ migration barrier demonstrated by density-functional theory (DFT) calculations illustrate the decreased Coulombic ion-lattice repulsion of Cu-Bi _2-x Se ₃ . Therefore, Cu-Bi _2-x Se ₃ 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-Bi _2-x Se ₃ 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-Bi _2-x Se ₃ 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.
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