From 0D to 3D: Controllable synthesis of ammonium vanadate materials for Zn2+storage with superior rate performance and cycling stability

Vanadium-based materials are one of the most promising cathodes for aqueous zinc ion batteries owing to their adjustable layered structure and high specific capacity. However, the sluggish Zn2+ diffusion kinetics and inferior structural stability still hinder their further development. Here, selective control of the structure of ammonium vanadate (NVO) materials is successfully achieved by a simple hydrothermal method, and the relationship between structure and performance is clarified. It was found that the amount of citric acid in the precursor solution is a vital factor for this morphology evolution. Density functional theory calculations show that the oxygen vacancies could modulate the electron structure of NVO and effectively weaken the electrostatic interaction between Zn2+ and the NVO lattice. Benefitting from the isotropic structure with abundant oxygen vacancies, the amorphous NVO nanodots exhibit superior reaction kinetics. The specific energy of 148.5 Wh kg-1 was achieved at a power density of 3300 W kg- 1, along with a high capacity retention of 81% even after 5000 cycles at 5 A g- 1. This work not only provides a new strategy for the controllable synthesis of vanadium-based materials but also reveals the great application potential of amorphous materials in metal-ion batteries.