Morphology, ionic diffusion and applicability of novel polymer gel electrolytes with LiI/I2

Abstract

Novel polymer gel electrolytes have been prepared by incorporating LiI–I₂ solutions into a polyethylene oxide matrix supported by a TiO₂ filler. The gel electrolytes, based on either acetonitrile or propylene carbonate solvents are compared with liquid standard ones and are examined by ⁷Li solid state nuclear magnetic resonance relaxometry and diffusion measurements. In parallel, the triiodide apparent diffusion coefficient has been determined by linear sweep voltammetry. The results are correlated with atomic force microscopic images of the electrolytes and give insight of the dynamic properties of the ions in the constrained polymer medium. Furthermore, the dissociation of the ions is estimated by relating the ionic conductivity to the ionic diffusion. As a prime application, the polymer gel electrolytes were incorporated in dye sensitized solar cells and the measured energy conversion efficiencies were successfully correlated with their morphological, diffusive and conducting properties.