The Electroactive Species and Electrolyte Solution Chemistry Importance in Non-Aqueous Mg Electrochemical Systems

The chemistry of the electrolyte solutions that enable reversible Mg deposition is not trivial. Such solutions are currently limited to ethereal solvents and most of them contain chlorides complexes. These ionic complexes have important role in the performance. However, the presence of chlorides in these solutions complicates the cathode side because such solutions are not compatible with the commonly used metallic current collectors for cathodes. Consequently, it is questionable whether it is possible to synthesize fully functional Cl-free electrolyte solutions suitable commercial Mg-ion batteries. Noked et al. reported that by adding DME to the precursor electrolyte [Mg2Cl3*6THF]+ [Ph3AlCl]- in THF, it was possible to create a new electroactive complex Mg salt, namely, [Mg-3.DME]2+ 2[AlPh3Cl]-, which solution performs better than the precursor’s solution. This solution introduces a new case of chlorides free electrolyte solution, with stabilized Mg2+ cations and anions containing chloride ligands which cannot lead to corrosion phenomena. In this work a full evaluation of selected electrolyte solution was carried out, considering rigorously the role of the electroactive species and the anion complexes in the electrochemical process. In addition, we study the effect of the anion on the electrochemical performance by comparing this solution with other previously presented solutions.