Magnesium Ions Storage in Molybdenum Oxide Structures Examined as a Promising Cathode Material for Rechargeable Magnesium Batteries

Magnesium batteries have attracted considerable attention as a promising technology for future energy storage because of their capability to undergo multiple charging reactions. However, most oxide materials utilized as hosts for magnesium batteries do not perform well at room temperature or in nonaqueous electrolytes. Herein, a host material, Na_0.04MoO₃·(H₂O)_0.49 is successfully developed through the chemical reduction of alpha-MoO₃, which enables magnesium storage reaction in a 0.5 m Mg(ClO₄)₂/acetonitrile electrolyte at 25 °C. Electrochemical analysis reveals that the cathode material possesses a discharge capacity of 157.4 mAh g⁻¹ at a 0.2 C rate. The Na_0.04MoO₃·(H₂O)_0.49 cathode material also exhibits a capacity retention of 93.4% after 100 cycles compared to the first cycle at a 2 C rate, with an average discharge voltage of −0.474 V versus activated carbon (≈2.16 V estimated discharge voltage vs Mg/Mg²⁺). The study findings demonstrate, for the first time, the potential of this material as a cathode for magnesium batteries at ambient temperatures and in nonaqueous electrolytes.