Environmentally Tolerant Ionic Hydrogel with High Power Density for Low-Grade Heat Harvesting

Harvesting low-grade heat by an ionic hydrogel thermoelectric generator (ITEG) into useful electricity is promising to power flexible electronics. However, the poor environmental tolerance of the ionic hydrogel limits its application. Herein, we demonstrate an ITEG with high thermoelectric properties, as well as excellent capabilities of water retention, freezing resistance, and self-regeneration. The obtained ITEG can maintain the original water content at ambient conditions (302 K, 65% relative humidity (RH)) for 7 days and keep unfreezing at a low temperature (253 K). It can even be self-regenerated and recovered to its original state after a water loss in high-temperature conditions. Furthermore, a high ionic Seebeck coefficient of 11.3 mV K-1 and an impressive power density of 167.90 mW m(-2) are achieved under a temperature difference of 20 K. A high power density of 60.00 mW m(-2) can also be maintained even at 258 K. After drying and regeneration, ITEG-re could even exhibit a higher ionic Seebeck coefficient of 11.8 mV K-1. Successful lighting of light-emitting diodes (LEDs) and charging of capacitors demonstrate the great potential of ITEG to provide continuous energy supply for powering flexible electronics.

Automated summary

In this study, a thermoelectric generator (ITEG) using an ionic hydrogel was developed to convert low-grade heat into electricity for flexible electronics. The ITEG exhibited high thermoelectric properties and excellent environmental tolerance, retaining water content and resisting freezing at low temperatures. The ITEG also demonstrated self-regeneration capabilities. It achieved a high ionic Seebeck coefficient and impressive power density under a temperature difference. The successful lighting of LEDs and charging of capacitors highlight the potential of ITEG in providing continuous energy supply for flexible electronics.