Constructing High‐Power N‐Type Thermocells via Fluoride‐Mediated Imidazole–Iodine Coordination

Abstract

ABSTRACT I − /I 3 − ‐based thermocells show great potential for low‐grade heat harvesting because of their affordability, adjustable electrochemical Seebeck coefficient ( S e ), and ease of device integration. However, current strategies of developing high‐performance I − /I 3 − ‐based thermocells usually result in substantial imbalance between S e and ultimate output power due to deteriorated ion transportation and replenishment. Herein, we propose a novel fluoride‐mediated coordination strategy to break this trade‐off. By introducing potassium fluoride and 1‐(2‐hydroxyethyl)imidazole (HEI) into the electrolyte, we engineer in situ formation of thermosensitive HEI‐I 2 F − coordinated complexes. These complexes undergo reversible temperature‐dependent precipitation and dissociation, creating a significant concentration ratio gradient, thereby remarkably increasing S e . Concurrently, the introduced ligand ions disrupt the original hydrogen bonding of water molecules, facilitating superior ion transport for increased output current. Consequently, the optimized thermocell achieves a high S e of 1.53 mV K −1 and a maximum power density of 124.74 mW m −2 at Δ T  = 30 K. This work provides a versatile and effective pathway toward high‐power thermocells for low‐grade heat harvesting.