Magnesium Ion Storage Properties in a Layered (NH<sub>4</sub>)<sub>2</sub>V<sub>6</sub>O<sub>16</sub>·1.5H<sub>2</sub>O Nanobelt Cathode Material Activated by Lattice Water
Luyao Wei, Ruqian Lian, Dashuai Wang, Yingying Zhao, Di Yang, Hainan Zhao, Yizhan Wang, Gang Chen, Yingjin Wei
Abstract
Magnesium ion batteries have attracted increasing attention as a promising energy storage device due to the high safety, high volumetric capacity, and low cost of Mg. However, the strong Coulombic interactions between Mg2+ ions and cathode materials seriously hinder the electrochemical performance of the batteries. To seek a promising cathode material for magnesium ion batteries, in this work, (NH4)2V6O16·1.5H2O and water-free (NH4)2V6O16 materials are synthesized by a one-step hydrothermal method. The effects of NH4+ and lattice water on the Mg2+ storage properties in these kinds of layered cathode materials are investigated by experiments and first-principles calculations. Lattice water is demonstrated to be of vital importance for Mg2+ storage, which not only stabilizes the layered structure of (NH4)2V6O16·1.5H2O but also promotes the transport kinetics of Mg2+. Electrochemical experiments of (NH4)2V6O16·1.5H2O show a specific capacity of 100 mA·h·g–1 with an average discharge voltage of 2.16 V vs Mg2+/Mg, highlighting the potential of (NH4)2V6O16·1.5H2O as a high-voltage cathode material for magnesium ion batteries.