Continuous harvesting of intermittent and continuous heats by a mixed ion/electron thermoelectric generator using an ionogel blended with carbon nanotube ionogels

<title>Abstract</title> <p> Ionic thermoelectric (TE) materials have drawn considerable interest because their thermopower can far exceed that of conventional electronic TE materials. They are typically implemented in ionic thermoelectric capacitors (ITECs) for heat harvesting. However, ITECs can harvest only intermittent heat, and there is no electricity generation under steady temperature. Here, we demonstrate a mixed ion/electron thermoelectric generator (MTEG) that can continuously harvest both intermittent and continuous heats into electricity. The active layer is an ionogel blended with single-walled carbon nanotubes (SWNTs), forming a mixed conductor in which the ionic liquid enables ion transport while the SWNT network provides electronically conductive pathways. Under a constant temperature gradient, the MTEG delivers a stable output voltage to an external load, closely resembling the behavior of conventional thermoelectric generators. The thermopower exceeds 11.3 mV·K ^− 1 , which is 1–2 orders of magnitude higher than the Seebeck coefficient of the best electronic TE materials. This operation is attributed to synergistic effects: hole tunneling across the SWNT network coupled with the large ionic thermopower arising from the Soret effect. </p>