Novel layered iron vanadate as a stable high-voltage cathode material for nonaqueous magnesium-ion batteries

Magnesium-ion batteries (MIBs) have been deemed as a promising alternative to lithium-ion batteries because they can employ a Mg metal anode, potentially yielding a higher energy density. However, the lack of cathode materials capable of the reversible Mg intercalation in non-aqueous electrolytes severely limits the commercialisation of MIBs. In this study, a novel cathode material, layered iron vanadate (FeV₃O₉·1.1H₂O), is proposed for use in non-aqueous MIBs. At 20 mA g⁻¹, FeV₃O₉·1.1H₂O registered a high reversible capacity and average voltage of 149 mAh/g and 2.53 V (vs. Mg/Mg²⁺), respectively. It also demonstrated a stable cycle life with an 85% capacity retention even after 500 discharge–charge cycles. The reversibility of the Mg intercalation reaction on this novel iron vanadate-based host was confirmed through elemental analyses, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (TEM). This study offers valuable insights that could facilitate the design and development of novel oxide-based materials as high-performance cathodes for non-aqueous MIBs.