Electrochemical Insertion of Magnesium in Metal Oxides and Sulfides from Aprotic Electrolytes

The electrochemistry of TiS 2 , ZrS 2 , RuO 2 , Co 3 O 4 , and V 2 O 5 has been studied in several organic solvents containing Mg ( ClO 4 ) 2 in view of their application as positive electrodes in rechargeable magnesium batteries. Only V 2 O 5 showed promising coulombic capacity and reversibility. Mg 2+ insertion into this oxide depends on the ratio between the amounts of H 2 O and Mg 2+ as well as on the absolute amount of H 2 O in the electrolyte. Water molecules preferentially solvating Mg 2+ ions appear to facilitate the insertion process. The highest coulombic capacities of up to 170 Ah/kg were reached in acetonitrile solutions containing 1 M Mg ( ClO 4 ) 2 + 1 M H 2 O .