Abstract
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 mAh·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.
Highlights
Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles
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
The energy density remained rather constrained by the cathode material, and the narrow potential window, corrosion, and safety problems posed by the electrolyte have hampered the commercial realization of these batteries
Summary
Salt dissolved in a less volatile solvent, would be desirable. Here, we present our results using magnesium bis(trifluoromethylsulfonyl)imide (Mg(TFSI)2) dissolved in triglyme. Our results validate that the Mg(TFSI)2–triglyme system, in addition to the reported glyme–diglyme system[5], can be used in rechargeable magnesium batteries in combination with high-voltage cathode materials. As a proof-of-concept, we propose a novel rechargeable magnesium battery system as shown, where ion-exchanged MgFeSiO4 and Mg metal are used as the cathode and anode, respectively, and Mg(TFSI)2–triglyme as the electrolyte. These materials would be highly beneficial for increasing the energy density of the electrode materials in magnesium batteries without imposing significant constraints on available resources. Capacity range was limited to 0.5 Mg21 per Fe
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