Microwave-assisted hydrothermal synthesis of NH4V3O8 microcrystals with controllable morphology

• Water-free NH4V3O8 microcrystals have been successfully synthesized by a microwave-assisted hydrothermal method.
• The crystal size and morphology of NH4V3O8 are governed by the pH value of the reaction solution, while there is smaller impact of the reaction temperature and duration.
• Electrochemical characterization reveals Li+ de-/intercalation attributed to the V5+/4+ and V4+/3+ redox couples, and a high initial discharge capacity of 378 mA h g−1.

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 μm length are found, while at pH 5.5 single microplates with hexagonal outline (30–40 μm) prevail. The electrochemical studies show reversible lithium de-/intercalation into the layered NH4V3O8 host structures with a maximum initial discharge capacity of 378 mA h g−1 at 10 mA g−1. However, there is no clear effect of the materials’ morphology on their electrochemical performance.

Figure optionsDownload as PowerPoint slide