Is One of the Least Coordinating Anions Suitable to Serve as Electrolyte Salt for Magnesium‐Ion Batteries?

Abstract Weakly coordinating anions (WCAs) are considered promising candidates for application as electrolytes in multivalent post‐lithium batteries. One strong candidate electrolyte salt Mg battery is [Mg(L) x ][Al(OR F ) 4 ] 2 (L=MeCN (acetonitrile), DME (1,2‐dimethoxyethane); =3, 6; R =C(CF 3 that contains [Al(OR − one of the least WCAs known. Here we present a novel synthetic route, which vibrational, NMR and XRD analyses show formation clean, pristine without common contaminants found published routes. The electrochemistry this pure [Mg(DME) (0.2 m DME) was investigated via cyclic voltammetry (CV). In contrast to previous publications using impure materials, CV showed no sign deposition from all conditions tested. This also holds when including additives LiCl, NaCl, MgCl , Li[BH or mixture /Mg[HMDS] (HMDS=hexamethyldisilazide) THF. Quantum chemical calculations suggested possibility anion decomposition at negative electrode, leading an electronically insulating MgF layer (rutile structure) on electrode materials hypothesis confirmed by XPS investigation electrodes exposed containing [Al(OC(H)(CF potentials, only presence electrolyte, but not related (which allowed deposit magnesium reversibly electrode).