Magnesium Ion Doping and Micro‐Structural Engineering Assist NH4V4O10 as a High‐Performance Aqueous Zinc Ion Battery Cathode

Abstract Layered ammonium vanadate materials exhibit significant mass‐specific capacity and ion transport rate due to their small molecular weight and large ionic radius. However, the strong electrostatic interactions of Zn 2+ and V–O bonds and the fragile ionic bonding of N‐H … O bonds hinder their development. Therefore, this work reports Mg 2+ doping NH 4 V 4 O 10 materials accompanied by flower‐like morphology to lower the migration energy barrier and inhibit amine dissolution. Owing to the 3D‐flower‐like morphology and the combined impact of Mg 2+ and structural water, the binding of Zn 2+ … V‐O is significantly enhanced and additional ion channels were constructed. Pre‐intercalated Mg 2+ enhances the structural integrity and prevents irreversible deammoniation from obtaining excellent cyclic stability. Density functional theory (DFT) calculations show that MNVO provides a smoother Zn 2+ diffusion path with a lower migration barrier. Benefited from these advantages, the MNVO cathode exhibits a high specific capacity of 410 mAh g −1 at 0.1 A g −1 , satisfactory cyclic stability (90.2 % capacity retention at 10 A g −1 after 5000 cycles), and capable rate ability (118 mAh g −1 at 25 A g −1 ) within 0.4‐1.5 V. Furthermore, the zinc ion storage mechanism in the MNVO cathode is investigated through multiple analyses.