Crystalline–amorphous heterointerface engineering in oxygen‐vacancy‐activated BiOCl for high‐performance aqueous zinc‐ion batteries

Abstract

The practical application of aqueous zinc‐ion batteries (ZIBs) is constrained by the intrinsic limitations of conventional cathode materials, including insufficient active sites, sluggish Zn ²⁺ diffusion kinetics, and structural instability upon repeated cycling. In this study, we propose a synergistic cathode–electrolyte co‐engineering strategy. Oxygen vacancies ( O _V ) engineered nanoflower‐like BiOCl featuring a crystalline‐amorphous heterostructure is designed, which establishes built‐in electric fields and tailors the local electronic structure to accelerate interfacial charge transfer. The amorphous regions provide abundant accessible active sites shorten Zn ²⁺ diffusion pathways and effectively alleviates the volume strain during Zn ²⁺ insertion/extraction. The I ⁻ / redox couple in the 2 M ZnSO ₄  + 0.2 M KI electrolyte contributes additional Faradaic capacity while cooperatively promoting the reversible conversion reaction of Bi ⁰ /Bi ³⁺ . The optimized cathode exhibits excellent Zn ²⁺ storage performance with a specific capacity of 349 mA h g ⁻¹ retained after 800 cycles at 3 A g ⁻¹ and 256 mA h g ⁻¹ remaining after 2600 cycles at 10 A g ⁻¹ . This work provides an effective design principle integrating defect‐mediated interfacial engineering with redox‐active electrolyte modulation for advancing high‐energy high‐power and long‐cycling aqueous ZIBs.