Synergistic Thermoelectric-Piezoionic Ionogel for Multimodal Energy Harvesting

Harvesting electricity from thermal and mechanical energy sources via thermoelectric and piezoionic effects offers a promising strategy for self-powered electronics. However, their practical applications are hindered by low and intermittent electricity outputs due to limited thermopower and local ion depletion of the electrolytes under mechanical stress, respectively. Here, a thermoelectric-piezoionic ionogel (TPIG) is developed that integrates ionic thermoelectric (i-TE) and piezoionic (PE) functionalities, enabling synergistic energy conversion under thermal gradients and mechanical compression. Owing to the synergistic i-TE and PE effects, TPIG exhibits a twofold increase in output voltage at a temperature difference of 3 K under 30% compressive strain (39 kPa). This enhancement stems from the chelation of redox ions within the ionic liquid, which induces a transition of the ionic liquid from n-type to p-type. This polarity transition effectively couples with piezoionic-induced selective ion migration under mechanical stress, which amplifies the ionic concentration gradient and significantly enhances the thermopower of TPIG. Scalable thermo-piezoionic generators composed of 16 TPIG units achieve an open-circuit voltage of 690 mV and exhibit thermal stability with continuous power generation under large temperature gradients of 80 K. They offer a new paradigm for adaptive energy harvesters operating in dynamic thermo-mechanical environments.