Solid Polymer Electrolytes Based on Gellan Gum and Ionic Liquid for Sustainable Electrochromic Devices

Materials sustainability is becoming increasingly relevant in every developed technology and, consequently, environmentally friendly solid polymer electrolytes (SPEs) based on gellan gum and different quantities of ionic liquid (IL) 1-ethyl-3-methyl-imidazolium-thiocyanate [Emim] [SCN] have been prepared and applied in electrochromic devices (ECDs). The addition of the IL does not affect the crystalline phase of gellan gum, and the samples show a compact morphology, surface uniformity, no phase separation, and good distribution of the IL within the carrageenan matrix. The developed SPE are thermally stable up to similar to 100 degrees C and show suitable mechanical properties. The most concentrated sample (39 wt % IL content) reaches a maximum ionic conductivity value of 6.0 x 10(-3) S cm(-1) and 1.8 x 10(-2) S cm(-1) at 30 and 90 degrees C, respectively. The electrochromic device (ECD) was fabricated with poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) as working electrode and the developed SPE was compared with an aqueous 0.1 M KNO3 solution. The electrochromic performance of the electrolyte was assessed in terms of spectroelectrochernistry, demonstrating a fully flexible ECD operating at voltages below 1.0 V. This novel electrolyte opens the door to the preparation of high performance sustainable ECD.

Automated summary

In this study, environmentally friendly solid polymer electrolytes (SPEs) based on gellan gum and ionic liquid (IL) were prepared and applied in electrochromic devices (ECDs). The developed SPEs showed good thermal stability, suitable mechanical properties, and high ionic conductivity. The electrochromic performance of the SPE was evaluated and demonstrated a fully flexible ECD operating at voltages below 1.0 V.