Ionic Liquid Boosted Conductivity of Biopolymer Gel Electrolyte

Abstract

Herein, we have developed a new biopolymer gel electrolyte based on xanthan, a material widely used in the food and pharmaceutical industry. The incorporation of the ionic liquids 1-butyl-2,3-dimethylimidazolium iodide (BMMI.I) and 1-ethyl-2,3-dimethylimidazolium iodide (EMMI.I) has significantly enhanced ionic conductivity by 136% and 181%, respectively. These ionic liquids possess a substantial permanent dipole moment, which can induce the alignment of other dipoles around them, through conformational changes. The interplay between the ionic liquid and the segmental motion of the polymer was investigated through temperature-dependent conductivity measurements using the Vogel-Tamman-Fulcher equation. Analysis of the complex dielectric (ε′and ε″) constants revealed the polarization effect of ionic species at the electrode/electrolyte interface. Additionally, the analysis of the complex electric modulus (M′and M″) and the loss tangent (tang δ) show that the incorporation of EMMI.I resulted in an electrolyte with the shortest relaxation time, indicating greater segmental motion of the polymeric chain, ultimately leading to higher ionic conductivity. DSSCs assembled with biopolymer gel electrolytes containing ionic liquids demonstrated an improvement in the short-circuit current, which is related to the high ionic conductivity.