Microwave-assisted hydrothermal synthesis of NH4V3O8 microcrystals with controllable morphology

Water-free NH4V3O8 microcrystals have been successfully synthesized by a microwave-assisted hydrothermal synthesis method. The products were characterized by means of X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, cyclic voltammetry, and galvanostatic cycling. The results show phase-pure products whose particle size and morphology can be tailored by varying the reaction conditions temperature, time, and initial pH value. For instance, at low pH (2.5-3) flower-like agglomerates with primary particles of 20-30 mu m length are found, while at pH 5.5 single microplates with hexagonal outline (30-40 mu m) prevail. The electrochemical studies show reversible lithium de-/intercalation into the layered NH4V3O8 host structures with a maximum initial discharge capacity of 378 mAh g(-1) at 10 mA g(-1). However, there is no clear effect of the materials' morphology on their electrochemical performance. (C) 2016 Elsevier Ltd. All rights reserved.