Stretchable and thermo-mechanical stable ionogels with high thermoelectric properties for respiratory sensing and energy harvesting

Abstract

Flexible and wearable thermoelectrics have attracted much attention due to their unique capability of converting body heat into electricity. However, the trade-off between good mechanical properties and high thermopower remains a big challenge. Herein, a general concept based on synergistic ion-ion/ion–dipole interactions and chemical-physical networks to fabricate ionic thermoelectric (i-TE) ionogels with outstanding mechanical properties and ultrahigh thermoelectric performances is developed. The as-prepared ionogel demonstrates high mechanical stretchability of up to 1160 %, ultralow hysteresis of 4.6 %, tensile strength of 5.25 MPa, toughness of 22.09 MJ/m3, as well as outstanding thermo-mechanical stability and temperature tolerance from −99 to 250 °C. Importantly, the ionogel exhibits a giant ionic Seebeck coefficient (Si) up to 28.43 mV K−1, superior ionic conductivity of 35.3 mS cm−1, and impressive power factor (PF) of 2.85 mW m−1·K−2 at 90 RH%. As a result, a record high ionic thermoelectric figure of merit (ZTi) of 6.9 is obtained. Stretchable thermoelectric materials are endowed with both giant thermovoltage and ZTi is rarely achieved in previous studies. Furthermore, the application in flexible and wearable i-TE sensors and energy harvesters is demonstrated to convert heat into electricity for sensing and human body energy harvesting. Therefore, the as-prepared stretchable i-TE materials show amazing potential for advanced wearable self-powered ionotronics.