Theory-experiment partnership applied to the spectroscopic analysis of a promising conditioning-free electrolyte for Mg batteries

• Different Mg complexes are identified in Raman spectra of a Mg-conducting electrolyte. • AIMD-simulated spectra support the analysis of experimental data. • Addition of Mg powder to MACC electrolyte leads to formation of electroactive species. The addition of Mg to the 1:1 MgCl 2 :AlCl 3 -dimethoxyethane system allowed to observe for the first time at the ν MgCl region, besides Raman bands at 213 and 221 cm −1 of the respective MgCl 2 (DME) 2 and [(μ-Cl) 2 Mg 2 (DME) 4 ] 2+ complexes, a new band at 236 cm −1 , which is belonging to the [(μ-Cl) 4 Mg 3 (DME) 5 ] 2+ species, as well supported by ab initio molecular dynamics (AIMD) simulations and “static” quantum-chemical (QC) calculations. Another band at 555 cm −1 is experimentally observed and shows good relationship with theoretical bands identified at 543 and 547 cm −1 , which correspond to the dimer and trimer, respectively. From this work on it may be used as a sensor to monitor DME coordination, once power spectra reveal strong contribution of the Mg-O-C-C-O- δ S mode as well as larger Raman scattering cross section for the trimeric species. This investigation’s results evidence that reductant Mg powder acts not only as a scavenger to remove deleterious species present in the electrolyte, but also leads to the formation of complexes considered electroactive.