Ammonium Vanadium Oxide Hydrate/Porous Activated Carbon Nanocomposite for High Energy Density Aqueous Ammonium Ion Storage

Ammonium ion storage is poised to revolutionize energy storage because of its affordability, safety, abundance of elements, and eco-friendliness. However, the potential of NH4+ ion storage has been elusive as a result of difficulties in NH4+ ion host materials development. For the first time, we have explored the NH4+ ion storage capabilities of a nanocomposite made of ammonium vanadium oxide (NVO) and porous activated carbon (PAC). This NVO–PAC nanocomposite boasts a specific capacitance of 527 mF cm–2, surpassing the 367 mF cm–2 value of NVO alone at a constant current density of 2 mA cm–2. The PAC and NVO combination significantly increases the specific surface area, contributing to the nanocomposite's enhanced specific capacitance. The synergistic mechanisms of deintercalation/intercalation and adsorption of NH4+ ions on the NVO–PAC further amplify its specific capacitance. Moreover, we have fabricated a symmetric NH4+ ion cell using NVO–PAC, delivering an outstanding energy density of 95 mWh cm–2 at a power density of 2400 mW cm–2 and exceptional cycling stability, retaining 100% of its original capacitance even after 104 cycles with 97% Coulombic efficiency.