High Capacity Rechargeable Magnesium-Ion Batteries Based on a Microporous Molybdenum–Vanadium Oxide Cathode

Abstract

The three-dimensional microporous framework of the oxide Mo2.5+yVO9+δ (containing Mo5+/6+ and V4+/5+) is defined by three-, six-, and seven-membered ring channels. Due to the oxidation–reduction properties of Mo and V ions and the large open tunnels that can provide a diffusion pathway for small ions, Mo2.5+yVO9+δ has been found to intercalate both Li+ ions, reported previously, and also Mg2+ ions in Mg-ion batteries. Cathodes composed of Mo2.5+yVO9+δ were discharged and charged in Mg-ion cells at current densities ranging from 2 mA/g (C/70) to 10 mA/g (C/12). Mg2+ ions can be inserted into and extracted from MgxMo2.5+yVO9+δ between ∼3.33 and 1.73 V vs Mg/Mg2+ at room temperature, with up to 3.49 Mg2+ ions per formula unit intercalated into the framework, corresponding to a capacity of 397 mAh/g (1st discharge) which is among the highest capacities reported for Mg-based batteries. Powder X-ray diffraction was used to determine the lattice parameters of MgxMo2.5+yVO9+δ (0 < x ≤ 3) compositions prepared by ...