Cation-Anchoring-Induced Efficient n-Type Thermo-Electric Ionogel with Ultra-High Thermopower.

Abstract

Ionogels have emerged as promising candidates for low-grade thermal energy harvesting due to their leak-free electrolytes, exceptional flexibility, thermal stability, and high thermopower. While substantial progress in the thermoelectric performance of p-type ionogels, research on n-type ionic materials lags behind. Striking a harmonious balance between high mechanical performance and thermoelectric properties remains a formidable challenge. This work presents an advanced n-type ionogel system integrating polyethylene glycol diacrylate (PEGDA), hydroxyethyl methacrylate (HEMA), 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), and bacterial cellulose (BC) through a rational design strategy. The synergistic combination of photo-polymerization and hydrogen-bonding networks effectively immobilizes imidazolium cations while enabling rapid chloride ion transport, creating a pronounced cation-anion mobility disparity that yields a substantial negative ionic Seebeck coefficient of -7.16 mV K⁻¹. Furthermore, BC's abundant hydroxyl groups establish multivalent hydrogen bonds within the ternary polymer matrix, endowing the composite with exceptional mechanical properties-notably a tensile strength of 3.2 MPa and toughness of 4.1 MJ m⁻³. Moreover, the ionogel exhibits sensitive responses to stimuli such as pressure, strain, and temperature. The thermoelectric modules fabricated can harness body heat to illuminate a bulb, showcasing great potential for low-grade energy harvesting and ultra-sensitive sensing.