TFSI BASED ELECTROLYTE SOLUTIONS FOR Mg BATTERIES

MgTFSI₂ is the only known ether-soluble “simple” magnesium salt. The lack of suitable electrolyte solutions in which Mg metal anodes exhibit electrochemically reversible striping/deposition behavior hinders the progress towards development of secondary magnesium batteries. MgTFSI₂/DME solutions were demonstrated to dissolve large quantities of MgCl₂ and produce electrolyte solutions with superior performance in terms of reversible behavior of Mg electrodes and a wide electrochemical window. However ethereal MgTFSI₂/MgCl₂ electrolyte solutions don’t reach the level of organometallic based electrolyte solutions in terms of prolonged reversibility of Mg anodes. We believe that the solutions purity level governs the overall electrochemical performance, especially in solutions where strong reducing moieties (i.e Grignard reagents) are not present to act as impurities scavengers. In this work, we improved the performance of the MgTFSI₂/MgCl₂ (DME) solutions through chemical and electrochemical conditioning and demonstrate the effect on the solutions’ electrochemical characteristics during repeated prolonged Mg deposition/dissolution processes. We demonstrate relatively high reversible behavior of Mg deposition/dissolution with crystalline uniformity of the Mg deposits, complemented by a fully reversible intercalation/de-intercalation process of Mg ions into Mo₆S₈ reference model cathodes.