An electroactive nanostructured silver niobium oxyfluoride (SNOF) was successfully synthesized through the mechanochemical reaction of AgF/AgF2 and Nb2O5. Throughout a wide composition range of x=1-4.5 (x=Ag:Nb), the AgF-based SNOF was shown to be a cubic perovskite structure. For AgF2-based SNOF, a cubic perovskite developed at x=1.5, a structural phase transition to monoclinic and tetragonal was observed at x=2.83 and x=4.5, respectively. The SNOF (AgF) perovskite phases with proper control of composition exhibited a three-electron silver reduction occurring at a voltage of >3 V at modest rates of discharge without the use of any conductive matrix.