Comparative Study of Conventional Electrolytes for Rechargeable Magnesium Batteries

Abstract Conventional magnesium salts are generally considered to be passivating to the magnesium anode, hence chloride‐based electrolyte additives are often added to circumvent this issue. As a result, the performance of conventional magnesium salts has rarely been assessed in a chloride‐free system. This work provides a comparative study on the electrochemical performance and interfacial reaction of four commercially available magnesium salts with tetrabutylammonium borohydride as moisture scavenger. Magnesium bis(hexamethyldisilazide) was found to be the most reductively stable and enabled excellent magnesium plating/stripping without chloride additive. Investigation of the solid electrolyte interphase revealed a thin organic polyether layer that was conducive to magnesium‐ion migration. The results also showed that a minuscule amount of chloride (20 mM) improved the reversibility of magnesium plating/stripping but was still corrosive towards the current collector, thus establishing that chloride‐free electrolyte is most appropriate for future development of rechargeable magnesium batteries.