Sol-gel derived Li-ion conducting polymer electrolytes

Organic-inorganic hybrids have recently become a remarkable family of amorphous polymer materials with promising potential applications. In the present study, sol-gel derived organic-inorganic hybrid electrolytes doped with lithium salts (LiCl, LiClO4) were produced from inorganic and organic precursors such as tetraethyl orthosilicate, poly( ethylene oxide), poly( ethylene glycol), propylene oxide, propylene carbonate, ethylene glycol, and 1,2-propylene glycol. The hybrid electrolytes were obtained in the form of flexible or glassy materials depending on the composition and heat treatment temperature ( ranging from 80 to 125 degrees C). The morphology, structure and elemental chemical composition of the electrolytes obtained were examined by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDS), FTIR spectroscopy, and X-ray diffraction (XRD). Infrared spectroscopy and SEM observation results indicate that the structural properties of the synthesized materials are significantly influenced by organic additives and the sol-gel preparation procedure. The formation of organic group - O - Si linkages was confirmed by infrared spectra in all of the electrolytes obtained. The results of FTIR analysis are in a good agreement with C-13 and H-1 MAS NMR spectroscopy measurements performed for the hydrolysed sols immediately before the gel transformation process and at early gel stages. These results have revealed an enhanced duration of the cross-linking process in the species prepared with low molecular mass glycols. Cells in an electrochromic window arrangement were prepared in order to observe the photometric and cyclic voltammetry characteristics of thin-film electrochromic systems with the investigated hybrid materials employed as electrolytes. The results indicate that the inorganic-organic hybrids synthesized in this work are promising electrolytes for thin film electrochromic systems based on WO3.