Electrochemical cycling of Mg in Mg[TFSI]2/tetraglyme electrolytes

The electrochemical reversibility of magnesium was observed in an electrolyte consisting of 0.5 M Mg[TFSI]2 in tetraglyme in the presence of a small amount of Mg[BH4]2. The cyclic efficiency of the cathodic/anodic process was found to increase initially with [BH4]− then plateau at about 75% beyond 6 mM in these experiments. This concentration is in the region of that indicated by Karl Fischer analysis of the electrolyte as required of [BH4]− as a dehydrating agent. Cyclic voltammetry showed the reduction onset potential at approximately − 0.35 V vs. Mg and subsequent oxidation around 0 V vs. Mg. Stable cyclic efficiency of approximately 75% over 500 cycles is demonstrated on a platinum substrate. Mg cycling on magnesium, copper and aluminium substrates all show stable cycling over 500 cycles with cyclic efficiency > 73%.