RESUMO
Rechargeable magnesium batteries are deemed as the next-generation secondary battery systems because of their high theoretical capacity and the terrestrial abundance of magnesium, which is used as the anode in these batteries. The cathode material is an important factor to improve the energy density of the magnesium batteries. In this study, we investigate olivine-type MgMnSiO4 cathode materials owing to their high theoretical capacity (>300 mA h g(-1)). The low-temperature synthesis of MgMnSiO4 suppresses anti-site mixing between Mg and Mn, which drastically improves the charge-discharge capacities of the magnesium battery cathode. Our results show that the suppression of the degree of anti-site mixing between Mg and Mn enhances the diffusion of Mg(2+) during magnesium (de)insertion, and therefore, it is a dominant factor that affects the electrochemical performance of olivine-type MgMnSiO4.
RESUMO
Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO4 demonstrates a high reversible capacity exceeding 300 Ah · g(-1) at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO4 with a magnesium bis(trifluoromethylsulfonyl)imide-triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems.