Inorganic Chemistry, Vol.55, No.5, 2558-2564, 2016
NaFe3(HPO3)(2)((H,F)PO2OH)(6): A Potential Cathode Material and a Novel Ferrimagnet
A novel iron fluorophosphite, NaFe3(HPO3)(2)((H,F)PO2OH)(6), was synthesized by a dry low-temperature synthesis route. The phase was shown to be electrochemically active for reversible insertion of Na+ ions, with an average discharge voltage of 2.5 V and an experimental capacity at low rates of up to 90 mAhg(-1). Simple synthesis, low-cost materials, excellent capacity retention, and efficiency suggest this class of material is competitive with similar oxyanion-based compounds as a cathode material for Na batteries. The characterization of physical properties by means of magnetization, specific heat, and electron spin resonance measurements confirms the presence of two magnetically nonequivalent Fe3+ sites. The compound orders magnetically at T-C approximate to 9.4 K into a state with spontaneous magnetization.