3D Hierarchical Electrodes Boosting Ultrahigh Power Output for Gelatin‐KCl‐FeCN<sup>4−/3−</sup> Ionic Thermoelectric Cells
Yuchen Li, Qikai Li, Xinbo Zhang, Biao Deng, Cheng‐Gong Han, Weishu Liu
Abstract
Abstract Ionic thermoelectric (i‐TE) cells, using ions as energy carriers, have the advantage of achieving a high voltage of 1−5 V at approximately ambient temperature, showing a promise as a technology for powering Internet‐of‐Things (IoT) sensors. However, the low output power of i‐TE cells restricts their applications. Here, a 3D hierarchical structure electrode is designed to enlarge the electroactive surface area, significantly increasing the thermogalvanic reaction sites and decreasing the interface charge transfer resistance. The quasi‐solid‐state gelatin‐KCl‐FeCN 4–/3– i‐TE cells achieve a record instantaneous output power density (8.9 mW m –2 K –2 ) and an ultrahigh 2 h output energy density ( E 2h ) (80 J m –2 ) under an optimal temperature range. An average E 2h value of 59.4 J m –2 is obtained over the course of a week of operation. A wearable device consisting of 24 i‐TE cells can generate a high voltage of 2.8 V and an instantaneous output power of 68 µW by harvesting body heat. A simple and easy‐to‐operate electrode optimization strategy is provided here to increase the long‐term output power performance of i‐TE cells. This work represents a promising approach to develop reliable and green power sources for IoT sensors near room temperature.