Magnesium Electrolyte Based on EMImBF4 and -[MgCl2]n for Secondary Magnesium Batteries

this report, a new magnesium ion electrolyte is proposed, based on δ-[MgCl2]n and ethylmethylimidazolium tetrafluoroborate (EMImBF4) ionic liquid. Anhydrous δ-[MgCl2]n was obtained by reacting metallic magnesium with n-chlorobutane in a strictly anhydrous atmosphere as described elsewhere. δ-[MgCl2]n consists of inorganic polymer chains where Mg atoms are bonded together by chloride bridges. The δ-[MgCl2]n chains show a high crystallographic disorder and reactivity toward Lewis bases. Twelve magnesiumconducting electrolytes with formula EMImBF4/(δ-[MgCl2]n)f with f ranging between 0 and 0.117 were prepared by dissolving directly δ-[MgCl2]n into EMImBF4; f is the molar ratio between δ-[MgCl2]n and EMImBF4. The metal concentration of the electrolytes was determined by ICP-AES. The correlation between structure, thermal properties and conduction mechanism of EMImBF4/(δ-[MgCl2]n)f was investigated by several techniques: (a) Medium- and Far-infrared spectroscopy, to reveal the structural features and interactions between the various components of each electrolyte; (b) Differential Scanning Calorimetry (DSC), to detect the thermal transitions; (c) Broadband Electric Spectroscopy (BES), to investigate the relaxation phenomena taking place in the materials and the conduction mechanism. In addition, a detailed study of the mechanism of ion conduction in these electrolytes was carried out by BES in the 10E-2 Hz to 10 MHz and -150°C to 150°C frequency and temperature ranges, respectively. These studies were performed by analyzing the imaginary and real components of conductivity and permittivity spectra by suitable models.