Synergistic Design of Composite Ionogels With Enhanced Thermoelectric Properties, Mechanical Stretchability, and Sustainable Recyclability

Polymer‐based ion thermoelectric materials are promising materials for energy conversion because of their sustainability, cost‐effectiveness, and diverse sources. However, their poor mechanical properties and low thermoelectric efficiencies limit their application. This study introduces a stretchable, recyclable composite ionogel formed through reversible hydrogen bonding between polyvinyl alcohol (PVA) and tetramethylpiperidine‐1‐oxyl‐oxidized cellulose nanofibres (CNFs), which confines the ionic liquid 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA) by establishing a dynamic network structure. Sodium dodecylbenzene sulfonate (NaDBS) incorporation enhanced the thermoelectric performance by increasing the migration rate difference between cations and anions and improved the mechanical strength through coordination with PVA. The resulting PVA‐CNF 3 ‐NaDBS 13 ‐IL 80 ionogel exhibited remarkable mechanical strength, with a tensile strength and elongation at break of 790 kPa and 669.72%, respectively. The ionogel also demonstrated excellent thermoelectric properties, with an ionic Seebeck coefficient, ionic conductivity, and ionic power factor (PFi) of 8.36 mV K −1 , 22.45 mS cm −1 , and 156.94 μW m −1 K −2 , respectively, at 40% relative humidity. Notably, the ionogel retained both its mechanical and thermoelectric performance after five recycling cycles because of its reversible hydrogen bonds and coordination interactions. This ionogel shows excellent potential for use in ionic thermoelectric capacitors, offering a high‐performance, recyclable, and flexible material for wearable thermoelectric devices and advancing sustainable energy systems.