Di-ureasil Hybrid Electrolytes Incorporating a New Proton Ionic Liquid

Abstract

The protic ionic liquid (PIL) N-butylimidazolium trifluoromethanesulfonate ([BIm][TfO]) was obtained for the first time and incorporated into a sol-gel-derived di-ureasil matrix with a concentration of X=5, 10, and 30%, where X is the ratio of the mass of PIL per mass of poly(oxyethylene). Four years after their synthesis, the resulting quasi-anhydrous electrolytes remained amorphous, homogeneous, flexible, and thermally stable below 200 degrees C. SEM/EDS data revealed the presence of the PIL at the surface of the xerogels with X>5%, demonstrating that this type of morphological characterization is mandatory to avoid misleading ionic conductivity values. The highest ionic conductivity was produced in the washed sample with X=30% (3.5 x 10(-5) and 2.1 x 10(-3) Scm(-1) at 25 and 170 degrees C, respectively). The present family of electrolytes yielded higher conductivities than the N-ethylimidazolium trifluoromethane-sulfonate-based analogues introduced earlier by our group and may thus be considered as promising candidates for applications in fuel cells.