Iodine‐Mediated Defect Engineering of Vanadyl Phosphate Cathodes for High‐Performance Aqueous Zinc‐Ion Batteries
Yulai Lin, Jianming Meng, Peng Hei, Yuqing Wang, Bo Li, Xiaoqi Sun, Yu Song, Xiaoxia Liu
Abstract
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.