Effect of heat treatment on positive electrode properties and crystal structures of Mo-modified MgMn2O4

MgMn2O4(MMO) has attracted attention as a positive electrode material for magnesium rechargeable batteries. To improve the electrode properties, we performed modification of MMO with a Mo compound and investigated the effects of heat-treatment temperature (600 to 800 degrees C) of the modification process on the electrode properties and crystal structures. The Mo-modified MMO were successfully synthesized by immersing MMO in an aqueous solution containing Mo ion, followed by heat treatment. Discharge/charge cycle tests revealed that Mo-modified MMO heat-treated at 700 degrees C exhibited the highest discharge capacity and cycle characteristics. Crystal-structure analyses using synchrotron X-ray diffraction data showed that heat treatment at higher temperatures could relax the distortion of the crystal structure, although it increased the amount of Mg and Mn cation mixing. Crystal structure change and surface modification with a Mo compound are considered to be factors for improving positive electrode properties of MMO. [GRAPHICS]