Synthesis and electrochemical study of Mg1.5MnO3: A defect spinel cathode for rechargeable magnesium battery

Mg1.5MnO3, a defect oxide spinel derived by the Pechini route, was tested as cathode for rechargeable magnesium battery. TEM and XRD analyses of Mg1.5MnO3 shows the formation of ∼100 nm sized nano particles in the cubic defect spinel structure (space group: Fd3m; unit cell: 0.833294 nm). Cyclic voltammetry illustrates a reversible reaction occurring between 0.3 and 1.5 V versus magnesium. Galvanostatic cycling of the Mg1.5MnO3 cathode exhibits a low capacity of ∼12.4 mAh/g up to 20 cycle with ∼99.9% Coulombic efficiency when cycled at a current rate of ∼C/27. XPS (X-ray photoelectron spectroscopy) surface probe of magnesiated/de-magnesiated electrodes confirm a change in the redox center of Mn-ions during intercalation/de-intercalation of Mg-ion from the Mg1.5MnO3 electrode. The low capacity of Mg1.5MnO3 electrode mainly stem from the kinetic limitation of Mg-ion removal from the defect oxide spinel as the electrochemical impedance spectroscopy results of electrodes after 1st and 2nd cycle show that charge transfer resistance, Re, increases post charge state whereas interfacial resistance, Ri, increases after discharge state, respectively.