Novel Mg7V4O16(OH)2·H2O and Mg3(VO4)2: preparation, characterization, and performance as lithium-ion anode materials

Abstract

Mg7V4O16(OH)2·H2O was prepared by improving the hydrothermal conditions and Mg3(VO4)2 was obtained by heat treatment of Mg7V4O16(OH)2·H2O at 700 °C. XRD shows a phase transition from a hexagonal structure to an orthogonal structure, which is confirmed by the HRTEM results. Mg3(VO4)2 keeps overall pencil-shaped SEM morphology with Mg7V4O16(OH)2·H2O but shows a lot of spaces due to the loss of hydroxyl groups and crystal water in the structure during heat treatment. Mg3(VO4)2 enjoys a narrower band gap in comparison with Mg7V4O16(OH)2·H2O. The space in Mg3(VO4)2 microstructure and its narrower band gap improve the transmission efficiency of Li+, reaching a stabile capacity of 151 mAh/g after cycling 100 times at a current density of 100 mA/g.