Soret Effect-Based Ionic Thermoelectric Converters: Principles, Device Physics, and Applications.

Ionic thermoelectric (iTE) materials have been attracting more and more attention, because they can be used to harvest heat into electricity through the Soret effect. In comparison with electronic thermoelectric materials, they have distinctive advantages including high thermopower, high mechanical flexibility, and low intrinsic thermal conductivity. But they cannot be directly adopted as the active materials of the conventional thermoelectric generators (TEGs) because the ions cannot transport across the electrodes into the external circuit. Several types of devices were reported to use iTE materials for heat harvesting. Their principles and device physics are notably different from the conventional TEGs. This article provides a review on the recent advancements in the understanding of ionic thermopower and the development of iTE-based energy converters. To have continuous power generation even under steady temperature gradient, the iTE materials should be integrated with electronic materials. Apart from waste heat harvesting, they can have important applications in other areas, such as self-powered sensors, human-machine interfaces, fire protection, smart buildings, wound monitoring/repair and iTE-enhanced catalysis. At last, perspectives including key challenges and opportunities toward scalable and robust iTE devices are provided.