Preparation, electrochemical properties and energy storage mechanism of vanadium-based Prussian blue analogues as cathode materials for aqueous ammonium ion batteries

To explore high-performance cathode materials for aqueous ammonium ion batteries (AAIBs), vanadium-based Prussian blue analogue composites (VFe-PBAs) were prepared by hydrothermal coprecipitation method to enhance the reversible storage of NH 4 + . Benefiting from the stable three-dimensional structure and spacious gap position, VFe-PBAs-2 cathode displays excellent electrochemical activity and rate performance, achieving a high specific capacity of 84.3 mA·h/g at a current density of 1000 mA/g. In addition, VFe-PBAs-2 cathode also shows impressive long-term cycle durabilitywith 85.2% capacity retention after 3×10 4 cycles at 5000 mA/g. The synthesized cathode materials combined with the high electrochemical activity of vanadium ions significantly promote the rapid transfer of NH 4 + . Furthermore, NH 4 + embedding/extraction mechanism of VFe-PBAs-2 cathode was revealed by electrochemical kinetics tests and advanced ex-situ characterizations. The experimental results demonstrate that vanadium-modified VFe-PBAs-2 as a cathode material can remarkably improve the capacity, electrochemical activity and cycling stability of AAIBs to achieve high performance NH 4 + storage.