Iodine‐Mediated Defect Engineering of Vanadyl Phosphate Cathodes for High‐Performance Aqueous Zinc‐Ion Batteries

Abstract Vanadyl phosphate (VOPO 4 ) is extensively studied as a cathode material for aqueous zinc‐ion batteries (AZIBs). However, due to sluggish ion migration and low electrical conductivity, VOPO 4 typically exhibits moderate specific capacity below 200 mAh g −1 . To address these issues, an iodine (I 2 )‐mediated etching method is proposed to enhance the electrochemical performance of VOPO 4 for AZIBs. This method effectively regulates structural defects in VOPO 4 . Initially, I 2 undergoes a disproportionation reaction with interlayer H 2 O in VOPO 4 , inducing crystal defects in the nanosheet structure. Additionally, the generated HI reduces V 5+ , further introducing oxygen vacancies in VOPO 4 . Both experimental and computational results indicate that moderate structural defects in VOPO 4 can synergistically improve the electron transfer and ion diffusion kinetics of the electrode. However, excessive structural defects lead to crystalline amorphization and structural pulverization of VOPO 4 , impeding Zn 2+ migration within the material. Therefore, the iodine‐mediated etched VOPO 4 electrode (VOP‐I4) exhibits a high specific capacity of 249 mAh g −1 at a current density of 0.2 A g −1 and a large energy density of 300 Wh kg −1 at a power density of 246.2 W kg −1 , outperforming most reported VOPO 4 ‐based materials for AZIBs. This study provides a new avenue for developing high‐performance VOPO 4 materials for energy storage applications.