Soft‐Chemistry Synthesis and Characterization of Bismuth Oxyfluorides and Ammonium Bismuth Fluorides

Abstract

Two bismuth oxyfluorides, BiOF and BiO 0.5 F 2 , have been prepared by soft chemistry. These two compounds are of interest for application as new type of positive electrode active materials in secondary lithium battery. BiOF was obtained directly from the fluorination of Bi 2 O 3 by a saturated aqueous solution of NH 4 F. BiO 0.5 F 2 was obtained by the hydrolysis of β‐NH 4 BiF 4 at 70°C. The ammonium bismuth fluoride β‐NH 4 BiF 4 , which is a new orthorhombic form of NH 4 BiF 4 , was obtained by reacting BiF 3 in a saturated aqueous solution of NH 4 F. Two other ammonium bismuth fluorides, (NH 4 ) 0.5 BiF 3.5 and NH 4 Bi 3 F 10 , were also prepared by annealing β‐NH 4 BiF 4 at a relatively low temperature under inert atmosphere. The existence of the fluorite (NH 4 ) 0.5 BiF 3.5 is reported for the first time in this paper.