Unraveling the solvates in a diethylene glycol dimethyl ether-based electrolyte: A computational-experimental spectroscopic contribution to Mg battery area

Abstract

• Vibrational spectroscopy is used to study Mg-conducting electrolyte in diglyme. • Computational modeling supports the analysis of experimental data. • MgCl + is preferentially formed in diglyme-based electrolyte. Composition-dependent vibrational spectra were measured for the 3:5 MgCl 2 :AlCl 3 (MACC)-diethylene glycol dimethyl ether (G2) electrolyte. Mg(II)- and Al(III)-G2 interactions were identified at the solvent region by the 840 and 868 cm −1 bands, respectively, and confirmed at the metal-O region between 300 and 530 cm −1 . The pivotal role of the solvent and the presence of one Cl - anion, at least, in the coordination sphere of the metal ions are discussed in detail. The Lewis base-acid reaction involving the starting materials leads to the preferential formation of [MgCl] + and [AlCl 4 ] - , in which the former is identified in the IR spectrum by a band established by us as a marker at around 280 cm −1 . Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations of vibrational spectra very well support the experimental data, confirming that the MACC-G2 electrolyte is not governed by higher Mg(II) complexes.