Pre-Intercalation of Metal Ions into Ammonium Vanadate Nanostructures toward Advanced Zinc Ion Batteries

Abstract

Aqueous zinc ion batteries (AZIBs) featuring low cost and high safety are attracting considerable interest. More recently, ammonium vanadate, characterized by its high specific capacity, is regarded as a promising cathode material for AZIBs. However, their unstable layered structures and sluggish reaction kinetics limit their further development. To overcome these limitations, metal ions (Na⁺ and Zn²⁺) are pre-intercalated into ammonium vanadate to modify the interlayer spacing and enhance charge transfer kinetics. Additionally, the impact of different pre-intercalated ions on the structure and properties of ammonium vanadate is systematically investigated. Furthermore, we successfully synthesized ammonium vanadate cathode materials (Na_0.13(NH₄)_0.48V₂O₅·0.6H₂O, Na_0.13-NVO) featuring stable nanostructures by optimizing the pre-embedded Na⁺ content. In this case, pre-intercalated sodium ions could expand the layer spacing of ammonium vanadate (9.14 Å), reduce the electrostatic interaction of Zn²⁺ with the V–O framework, and boost the Zn²⁺ diffusion rate. Benefitting from these strengths, the Na_0.13-NVO electrode exhibits a specific capacity of 365.4 mAh g^–1 at 0.5 A g^–1, along with a good cycling stability of 98.1% capacity retention over 2000 cycles at 5 A g^–1. This work supplies further insights into designing ammonium vanadate with pre-embedded metal ions and aids the development of high-performance AZIB cathodes.