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.