Host–Guest Complexation of α‐Cyclodextrin and Triiodide Ions for Enhanced Performance of Ionic Thermoelectric Capacitors

Abstract Ionic thermoelectric materials have emerged as a promising avenue for harvesting low‐grade waste heat, with significant potential for applications in wearable electronics. This study introduces a novel design for ionic thermoelectric capacitors (ITECs) by incorporating host–guest complexation between α–cyclodextrin (α‐CD) and triiodide ions (I 3 − ). The strong host–guest complexation between α‐CD and I 3 − confines the diffusion of I 3 − within the cylindrical cavities of α‐CD, as evidenced by UV–vis spectroscopy and 13 C‐NMR analysis. This confinement enhances the ion mobility difference between I 3 − and sodium ions, which in turn significantly boosts the ionic thermopower of the polyvinyl alcohol/α‐CD/NaI hydrogels. Accordingly, the optimized sample achieves an impressive positive ionic thermopower of 14.24 mV K −1 and a high ionic power factor of 477.2 µW K −2 m −1 . Furthermore, the stretchable ITEC demonstrates a substantial power density of 5.9 mW m −2 . When integrated into a 3‐leg device, a stable thermovoltage of 176 mV is generated under a temperature gradient of 4.4 K, thus highlighting the potential of this system for efficient thermal energy harvesting.