Enhanced electrochemical properties of MgCo2O4 mesocrystals as a positive electrode active material for Mg batteries

Mesocrystals of MgCo2O4 spinel oxide exhibiting porous and single-crystalline structures were synthesized by the reaction of magnesium ions with calcite-type CoCO3 mesocrystal precursors grown in micrometer-sized agar gels. The mesocrystals consisted of single-crystalline porous grains measuring 200-300 nm in diameter with iso-oriented subunits of approximately 10 nm. The single-crystalline porous framework structure of the MgCo2O4 mesocrystals enhanced the discharge capacity and positively shifted the discharge potential compared with MgCo2O4 nanoparticles prepared by the inverse co-precipitation method. These enhancements were attributed to a combination of the high specific surface areas of the mesocrystals and the high connectivity of the magnesium ion diffusion paths in the solid-phase.