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.

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