Toward High Voltage Mg-Ion Battery Cathode Via a Solid-Solution Cr-Mn Spinel Oxide

Abstract

The capability of the tailored solid-solution spinel, MgCrMnO4, is evaluated by theoretical and experimental approaches. Lattice Mg2+ in the designed oxide is electrochemically utilized at high potentials in a non-aqueous electrolyte. Complementary evidence supports bulk Mg2+ (de)intercalation throughout the designed oxide frame where strong electrostatic interaction between Mg2+ and O2- exists. Mg/Mn antisite inversion in the spinel is lowered via post-annealing to further improve Mg+2 mobility. Spinel lattice is preserved upon removal of Mg2+ without any phase transformations, denoting structural stability at the charged state at a high potential. In the remagnesiated state, insertion of Mg2+ into interstitial sites in the spinel is detected possibly resulting in partial reversibility which needs to be addressed for structural stability. The observations constitute a first clear path to the development of a practical high voltage Mg-ion cathode using a spinel oxide.