Development of Magnesium Borate Electrolytes: Explaining the Success of Mg[B(hfip)4]2 Salt

Magnesium batteries are one of the most promising post-lithium technologies. One main challenges preventing its commercialization is to find an efficient and safe electrolyte. The electrolyte, playing role blood in a battery, interacts with all battery components must be highly compatible them. development Cl-free electrolyte systems desired avoid corrosion issues, many studies suggest magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2) as best candidates terms electrochemical properties chemical stability. Here we present in-depth analysis unique structure this salt interactions generated among dissociated ions. results show delicate balance between electron-withdrawing effects ligand stabilization B(hfip)4−, crucial from point view electrolytes. Moreover, bulk nature B(hfip)4− limits anion-cation contacts infrequent through fluorine atoms. This has consequences not only for ion transport but also hindering anion decomposition towards formation MgF2. Taken together, managed demystify exclusive anion, thereby allowing further rational new structures.