Anatase titania as magnesium host in Mg ion rechargeable battery with magnesium perchlorate/ethylmagnesium bromide electrolytes

This study compares the electrochemical charge/discharge performance of anatase titania-based Mg ion batteries constructed by using two different electrolytes, magnesium perchlorate (MPC) and ethylmagnesium bromide (EMB). It is observed that when MPC is the electrolyte, anatase TiO₂ (25 nm) accommodates < 0.01 Mg²⁺/formula unit (F.U.) at 25 °C and the capacity remains the same at 60 °C. On the other hand, when EMB is the electrolyte, it is possible to store ~ 0.02 Mg²⁺/TiO₂ F.U. at 25 °C and 0.06 Mg²⁺/TiO₂ F.U. at 60 °C. These values were further verified and confirmed by energy-dispersive X-ray spectroscopy. X-ray diffraction and atomic force microscopy studies suggest that the working electrodes and the reference electrodes in both these batteries are maintained in good condition after 4 charge/discharge cycles. Electrochemical impedance studies provide evidence that the polarization resistance of the cell with EMB as electrolyte decreases when the temperature is raised from 25 to 60 °C, whereas the trend is the opposite when the electrolyte is MPC. This study provides crucial evidence that the reactivity of Mg surface is one of the most important factors to attain better battery performance.