Bioinspired water-driven ion reciprocating migration enables continuous power generation in cellulose-based ionic thermoelectrics

Efficient harvesting of low-grade waste heat is crucial for global sustainable energy development. The ionic thermoelectric (i-TE) materials, operating on the ionic thermodiffusion (Soret effect), have attracted significant attention due to their high thermopower. However, their inherent intermittent operation mode limits energy harvesting efficiency and severely hinders practical applications. Inspired by the natural water and ions transport structures within trees, this study develops an i-TE material, (LCP/KI) i-TE, using lignocellulose (LC) as a three-dimensional framework and polyvinyl alcohol/potassium iodide (PVA/KI) as the electrolyte. Leveraging the unique aligned porous structure of LC, this material successfully combines the Soret effect with water-driven ion transport for the first time, achieving reciprocating migration of ions under a constant temperature difference. This biomimetic ion reciprocating migration strategy not only enables the (LCP/KI) i-TE to achieve a high ionic Seebeck coefficient of 35 mV K −1 under small temperature differences (<1 K), but also overcomes the core bottleneck of conventional ionic thermoelectric capacitors (i-TECs)—the necessity for intermittent operation due to ion polarization saturation. This innovation transforms the operation mode from a conventional four-stage cycle (with only two productive stages) into a simplified two-stage mode that continuously outputs power throughout the entire process. The assembled (LCP/KI) i-TEC operates stably with a permanently connected external circuit and can power electrical appliances such as light-emitting diodes (LEDs) and small calculators. This ion reciprocating migration strategy that provides a straightforward and efficient pathway for achieving continuous power output from i-TECs, opening new avenues for the sustainable harvesting and utilization of low-grade thermal energy.