Interfacial Effect Boosts the Performance of All-Polymer Ionic Thermoelectric Supercapacitors

Ionic thermoelectric supercapacitors (ITESCs) have recently been developed for converting low-grade waste heat into electricity. Until now, most reports of ITESCs have been focused on the development of electrolytes, which then have been combined with a specific electrode material. Here, it is demonstrated that the electrode is not only critical for electrical energy storage but also greatly affects the effective thermopower (S-eff) of an ITESC. It is shown that the same ion gel can generate a positive thermopower in an ITESC when using gold nanowire (AuNW) electrodes, while generating a negative thermopower when using poly(3,4-ethylendioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes. The achieved negative sign of the S-eff could be attributed to the Donnan exclusive effect from the polyanions in the PEDOT:PSS electrodes. After examining the thermovoltage, capacitance and charge retention performance of the two ITESCs, it is concluded that PEDOT:PSS is superior to AuNWs as electrodes. Moreover, a new strategy of constructing an ionic thermopile of multiple p- and n-type legs is achieved by series-connecting these legs with same electrolyte but different electrodes. Using interfacial effect at ionic gels/PEDOT:PSS electrode interface, an enhanced thermoelectric effect in ITESCs is obtained, which constitutes one more step towards efficient, low-cost, flexible, and printable ionic thermoelectric modules for energy harvesting.

Automated summary

This study demonstrates that the electrode used in an ionic thermoelectric supercapacitor (ITESC) is critical both for energy storage and for determining the effective thermopower. It is shown that different electrode materials can lead to positive or negative thermopower. Furthermore, the study concludes that PEDOT:PSS electrodes are superior to AuNWs electrodes in terms of thermovoltage, capacitance, and charge retention performance. Additionally, a new strategy of constructing an ionic thermopile is achieved by series-connecting different legs with the same electrolyte but different electrodes, resulting in enhanced thermoelectric effect in ITESCs.