Self-activation effect in bimetallic MgMn2O4 and boosting its electrochemical performance using metal-organic framework template for magnesium-ion battery cathodes

Abstract

Spinel MgMn2O4, an alternative Mg-ion battery cathode material, shows great promise owing to its high redox potential. However, large volume change and polarization occur because of the phase transitions between tetragonal spinel MgMn2O4 and cubic rock salt Mg2Mn2O4 during the Mg2+ insertion/extraction process, which reduces the cyclability and coulombic efficiency. Herein, we develop an efficient method to prepare cubic spinel MgMn2O4 cathode materials by annealing bimetallic metal-organic frameworks. The cathode exhibits excellent cyclability even at a high rate owing to its well-confined hierarchical structure with fast ion diffusion channels. During the cycling process, a self-activation effect is gradually conducted in MgMn2O4, which is crucial for improving the kinetics of Mg2+-ions in the host spinel structure. This activation endows the MgMn2O4 cathode with an obvious platform at ∼2 V vs. Mg/Mg2+ in full cells, which provides novel insights for developing high-performance Mg-ion battery cathode materials.