High Capacity Rechargeable Magnesium Ion Batteries Based on a Microporous Molybdenum Vanadium Oxide Cathode
The three dimensional microporous framework of the oxide Mo2.5+yVO9+d (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+d has been found to intercalate both Li+ ions, reported previously, and also Mg2+ ions in Mg ion batteries. Cathodes composed of Mo2.5+yVO9+d 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+d 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+d (0 x 3) compositions prepared by