Unraveling Dual Mechanisms in Quasi-Layered Bi2O2Se via Defect Modulation for High-Performance Aqueous Zn-Ion Batteries

Developing cathode materials for aqueous zinc-ion batteries (ZIBs) that offer high capacity, rapid charge–discharge rates, and prolonged cycle life remains a significant challenge. This study explores the use of zipper-type Bi₂O₂Se nanoplates modified by selenium vacancy (V_se) modulation, which reduces electron scattering, enhances carrier mobility in [Bi₂O₂] conducting channels, and decreases coulombic interactions within electrostatic layers. The introduction of Se vacancies facilitates electron transfer from the host to [Bi₂O₂] channels and reduces scattering in the [Bi₂O₂] framework, thus improving carrier mobility. These Se-poor Bi₂O₂Se nanoplates demonstrate a greater affinity for zinc ions, reduced diffusion barriers, and faster transport kinetics, which enable more efficient Zn-ion insertion, tripling the electrochemical capacity, improving rate capabilities, and extending cycling life. Enhancements such as reinforced structural integrity and expanded interlayer spaces support a dual Zn-ion-driven mechanism involving both insertion and conversion reactions, essential for superior electrochemical storage performance. The results include an impressive discharge/charge capacity of 380.3 mA h g⁻¹ at 0.1 A g⁻¹, a cycle life of up to 10 000 cycles at 5 A g⁻¹, and a current tolerance exceeding 10 A g⁻¹. This research highlights how nano- and defect engineering of Bi₂O₂Se can significantly enhance ionic conductivity, expedite electron transfer, and improve Zn-ion diffusion.