An Ionic Thermoelectric Generator with a Giant Output Power Density and High Energy Density Enabled by Synergy of Thermodiffusion Effect and Redox Reaction on Electrodes

Abstract Ionic hydrogel thermoelectric generators (ITEGs) are becoming increasingly popular in effective recovery of low‐grade waste heat, but they suffer from relatively low output power density and energy density. In this work, by utilizing the synergetic strategy of thermodiffusion effect and redox reaction on electrodes, an ITEG is demonstrated which demonstrates impressive thermoelectric conversion properties. On the one hand, an interpenetrating network structured ionic gel with temperature‐sensitive phase transition behavior is designed as thermoelectric material to achieve a very high thermopower of 40.60 mV K −1 at a temperature gradient (Δ T ) of 5 K. On the other hand, polymer redox polyaniline (PANI) is appended on the carbon weaved fabric (CWF) electrode to augment heat‐to‐electricity storage and output power performance. It is found that the PANI@CWF electrode assists to realize a larger current density output, 1 h output energy density ( E 1h ) (570 J m −2 ) at a Δ T of 20 K and a maximum normalized instantaneous output power density of 11.31 mW m −2 K −2 are obtained, which is a record‐breaking result among the reported quasi‐solid‐state ITEGs. A feasible routine to design the top‐performing ITEGs is verified, which shows commercial promise for continuously powering electronic devices such as sensors and wearable electronics.