A Zwitterionic Liquid Electrolyte for Magnesium Batteries

Rechargeable magnesium batteries are promising energy storage devices due to their high theoretical capacity. However, currently a crucial hindrance for their realization is the limited number of suitable electrolytes, all of which show severe disadvantages. We circumvent volatility, flammability, and instability issues of other systems by presenting an electrolyte based on magnesium borohydride and the zwitterionic liquid (ZIL) 1-butyl-3-methylimidazol-2-ylidene borane. We investigate the structure and properties of the electrolyte and compare it to a similar conventional system. Pronounced intermolecular interactions in the new electrolyte are investigated by H-1 and B-11 NMR spectroscopy. We also characterize galvanostatic cycling and deposition of magnesium on different electrodes and analyze the deposited material. Because of high reversibility and stability of the ZIL based electrolyte system, it shows promising potential for future magnesium based batteries.