Magnesium\nand Aluminum in Contact with Liquid Battery\nElectrolytes: Ion Transport through Interphases and in the Bulk

A significant challenge\nin improving Mg and Al batteries is the\nlimited understanding of the solid electrolyte interphase (SEI) and\nits evolution under operating conditions. Additionally, the cationic\ntransference number of related electrolytes is crucial for their performance\nas well as potential dendrite formation yet it is only rarely determined\nexperimentally. Here, we study Al and Mg systems using Grignards as\nelectrolytes for the Mg case and an ionic liquid electrolyte for the\nAl case. The activation energies associated with ion transport through\nthe SEI suggest that it initially contains a high contribution from\nliquid pathways for the Mg case and is dense for the Al case, but\nbecomes fully dominated by liquid pathways after a longer contact\nwith the electrolyte. The initial effective Mg cationic transference\nnumber of the Grignards is close to zero and increases significantly\nafter only one cyclic voltammetry cycle.