Dynamic Hydrogen‐Bond Networks Enable Long‐Lived Ionic Thermoelectric Materials With High Power Density

Achieving a balance between high power density and long‐term operational stability remains a major challenge for ionic thermoelectric materials, with reported stable operation typically limited to under a week. To overcome this limitation, here we present a hydrogen‐bond network approach to regulate ion transport. By impregnating a hydroxyl‐functionalized ionic liquid (HOEtMIM:Cl) into a porous carbon scaffold, we fabricate a composite featuring a dynamic hydrogen‐bond network. This network not only facilitates ordered cation migration through carbon channels, markedly enhancing thermoelectric current and power density, but also effectively traps water molecules to improve environmental stability. Notably, the composite achieves a high thermopower of 26.9 mV K − 1 and a peak power density of 0.95 W m − 2 under a 20 K temperature difference. And it sustains stable operation for over 46 days without external energy storage. An integrated device built from this material can directly power small electronics such as thermohygrometers, demonstrating its practical potential for low‐grade waste‐heat recovery. This study establishes a new design paradigm for high‐performance, long‐lived ionic thermoelectric materials.