Microscopic interactions in nanocomposite electrolytes

Nanocomposite electrolytes of a fully amorphous trifunctional polyether (3P EG) and poly(methylene ethylene oxide) (PMEO) have been complexed with two lithium salts and nanoparticulate (similar to 20 nm) fillers of TiO2 and Al 2O3. Addition of the fillers to the polymer salt complexes shows a signific ant change in the conformational modes of both polymers, especially the D-L AM region between 200 and 400 cm(-1), indicating a reduced segmental flexib ility of the chain. These changes are more pronounced with the use of TiO2 than Al2O3. Incorporation of the nanoparticulate fillers to the electrolyte s fails to influence the degree of ion association, suggesting that the num ber of charge carriers available for conduction in both polymers using both LiClO4 and LiCF3SO3 is not the source of any conductivity increase. Additi on of the fillers, which was seen to increase the conductivity in PEG-based systems, generally lowers the conductivity in the present PMEO systems, wh ile the addition of TiO2 has little or no effect except in the cases of 3PE G 1.5 and 1.25 mol/kg LiClO4. In this case, 10 wt % TiO2 provides a conduct ivity increase of half an order of magnitude at approximately 60 degreesC. We also report for the first time a Raman spectroscopy investigation into t he PEG-based nanocomposite electrolytes. The present results are discussed in terms of the electrostatic interactions involving dielectric properties of the fillers, of special interest being the interactions between the poly mer and the fillers and between the ionic species and the fillers, when the effect of crystallization can be ignored.