Electrolytes for secondary Li and Mg batteries

The development of innovative electrolytes is one of the most crucial targets in order to devise secondary batteries running on alkaline- and alkaline-earth elements characterized by a high specific energy and power and an extensive cyclability, able to provide power for a wide range of applications ranging from portable electronic devices to light-duty electric vehicles. The electrolytes must satisfy very demanding requirements, including: (a) easy migration of the alkaline- and alkaline-earth cations between the electrodes of the battery; (b) high compatibility with all the other functional materials used in the assembly of the device; (c) wide potential window and excellent stability. This report describes the preparation and characterization of innovative families of electrolytes meant to address these issues and opens new and promising avenues for the research in this field. One approach is the development of nanocomposite polymer electrolytes (nCPEs) consisting of PEG400 and a fluorinated nanofiller (e.g., titanium or iron oxide) whose surface anion groups are neutralized with Li+ cations. These nCPEs are single-ion conductors, and at room temperature present a Li+ conductivity of ca. 10-5 S/cm. The second electrolytes are based on -MgCl2 and an ionic liquid obtained by mixing EMImCl with AlCl3. The resulting electrolyte is suitable for application in secondary Mg batteries, and demonstrates: (1) a conductivity at room temperature of ca. 10-2 S/cm; and (2) a good cyclability in single cell tests. The chemical composition of the electrolytes is analyzed by ICP-AES and microanalysis. The thermal properties are investigated by HR-TG and DSC measurements. The structure and the interactions in materials is studied by vibrational spectroscopies (FT-MIR and FT–FIR). The electric response is elucidated by Broadband Electrical Spectroscopy (BES). Results allow to propose a conduction mechanism and to define the interplay existing between structural, thermal transitions and electric properties of proposed innovative electrolytes