Promoting Reversible Cathode Reactions in Magnesium Rechargeable Batteries Using Metastable Cubic MgMn2O4 Spinel Nanoparticles

Magnesium rechargeable batteries are candidates for post-lithium-ion batteries owing to the low price and superior theoretical volume energy density of Mg anodes. As a promising cathode material, MgMn2O4 spinel has a high energy density with a high operating voltage, and a relatively high ionic conductivity. However, the tetragonal symmetry of MgMn2O4, originating from the Jahn-Teller effect of Mn3+ ions, causes irreversible structural changes during the charge/discharge process, leading to poor reversibility. We developed metastable cubic MgMn2O4 spinel nanoparticles using the hot-injection method under low-temperature solvothermal conditions. Compared to tetragonal MgMn2O4, its cubic phase exhibited a superior reversible capacity, both experimentally and theoretically, at room temperature.