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

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 Zn2+ and V-O bonds and the fragile ionic bonding of N-(HO)-O- horizontal ellipsis bonds hinder their development. Therefore, this work reports Mg2+ doping NH4V4O10 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 Mg2+ and structural water, the binding of (Zn2+V)-V- horizontal ellipsis -O is significantly enhanced and additional ion channels were constructed. Pre-intercalated Mg2+ enhances the structural integrity and prevents irreversible deammoniation from obtaining excellent cyclic stability. Density functional theory (DFT) calculations show that MNVO provides a smoother Zn2+ 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.