Ionic Liquid-Inspired Highly Aligned Fibrous Ionogel for Boosted Thermoelectric Harvesting

Abstract

Ionogels represent promising materials for thermoelectric generators that efficiently convert low-grade heat into electricity due to their flexibility, stability, nonvolatility, and high thermopower. However, improving their thermoelectric performance presents challenges stemming from the complex interplay between ionic conductivity and thermal conduction. In this study, we developed a highly oriented nanofibrous ionogel membrane through the electrospinning of poly(ethylene oxide) (PEO) blended with a linear CO₂-derived polycarbonate oligomer and an ionic liquid, ethylmethylimidazolium dicyanamide. The ionic liquid facilitated the formation of highly aligned nanofiber structures, which demonstrated superior ionic conductivity and reduced thermal conduction compared to the bulk counterparts, primarily due to the size effect inherent in nanofibers. Additionally, the incorporation of CO₂-derived polycarbonate can increase the amorphous region of the PEO matrix and strengthen the ion-polymer interaction without compromising the orientation of the nanofibers thanks to its compatibility with PEO and its abundance of electron-withdrawing carbonate groups. This strategy effectively decouples ionic conductivity from thermal conduction, thereby enhancing the thermoelectric efficiency of ionogels. This advancement paves the way for the development of nanofibrous ionogels for use in flexible electronics and energy harvesting applications.