New hybrid inorganic–organic polymer electrolytes based on Zr(O(CH2)3CH3)4, glycerol and EMIm-TFSI ionic liquid

This report presents detailed studies on the elemental analysis, vibrational spectroscopy, thermal stability and electrical spectroscopy of two new hybrid inorganic–organic polymers which have been synthesised by a sol–gel method using glycerol and zirconium(IV)butoxide as precursors. These materials have been doped by means of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIm-TFSI) ionic liquid (IL), which is insoluble in water. The elemental composition of the obtained polymers Zr(C₆O₅H₁₁)] (1) and Zr(C₁₁O₄H₃₁)] (2) has been determined by CHN analysis and by ICP-AES measurements. FT-IR and FT-Raman spectroscopy investigations have been performed to study the molecular structure of the polymers and the interactions of EMIm-TFSI with the host networks. Differential scanning calorimetry measurements show the presence of at least one glass transition temperature (T_g) in both 1 and 2 materials. The broadband dielectric spectroscopic measurements have been carried out between 10⁻² Hz to 10 MHz from −100 °C to 100 °C with a 5 °C step. The conductivities of the polymers 1 and 2 have been found to be in the order of 10⁻⁸ to 10⁻¹¹ S cm⁻¹ at 25 °C, so they can be defined as dielectric materials. After doping 2 with EMIm-TFSI, the conductivity at 25 °C of the obtained complex Zr(C₁₁O₄H₃₁)]₁₅/(EMIm-TFSI) (2′) increased three orders of magnitude resulting ca. 10⁻⁵ S cm⁻¹. The permittivity spectra revealed two relaxation bands which were attributed to the α relaxation modes of the polymer networks.