Electrospun V2MoO8 as a cathode material for rechargeable batteries with Mg metal anode

With the increasing global demand for large-scale electrical energy storage , rechargeable Mg-based batteries are preferable due to their substantial prospective benefits in terms of raw abundance, theoretical capacity, and operational safety. Herein, we demonstrate for the first time V 2 MoO 8 synthesized by a facile electrospinning method as a cathode material for rechargeable magnesium batteries with the electrolytes containing Mg 2+ or Mg 2+ /Li + ions. SEM and HRTEM indicate that the V 2 MoO 8 sample presents wedged-shaped cuboid, 300–500   nm (thickness) ×4–6   µm (length) and its monoclinic phase structure provides a interlayer distance of 4.20   Å. As cathode material, V 2 MoO 8 is discharged/charged in a specially self-designed mould battery using Mg metal anode at current densities from 20 to 500   mA   g −1 . It delivers a high initial discharge capacity of 312   mA   h   g −1 with the initial coulombic efficiency of 87.2% at 20   mA   g −1 in 0.4   M (PhMgCl) 2 -AlCl 3 /1.0   M LiCl/THF electrolyte and presents good cycling and rate performance. XPS analysis reveals that both Mg 2+ and Li + ions take part in the cathode intercalation reaction, along with the valence changes of Mo/V ions. Additionally, a reversible capacity of ca. 210   mA   h   g −1 is obtained in Mg 2+ electrolyte with the 1st cycle efficiency of 94% at 60   °C. The poor capacity retention is partially attributed to the irreversible phase change to amorphous state of V 2 MoO 8 .