Giant Power Output from Ionic/electronic Hybrid Nanocomposite Thermoelectric Converter Under Constant Temperature Gradient.

Thermoelectric (TE) materials that directly convert heat to electricity are of great significance for sustainable development. However, TE generators (TEGs) made from electronic TE materials suffer from low Seebeck coefficient (10^-2-10⁰ mV K^-1). While ionic TE capacitors based on ionic conductors exhibit high thermovoltage (10⁰-10² mV K^-1), ionic TE capacitors provide power discontinuously only under variation of temperature gradient as ions cannot transport across electrodes to external circuits. Herein, an ionic/electronic hybrid nanocomposite TE converter (NCTEC) by integrating carbon nanotube/polylactic acid nanofibrous fabrics (CPNF) with gelatin ionogel is reported. The resulting NCTEC exhibits a record-high output power density normalized by squared temperature gradient (P_ave/ΔT²) of 1.72 mW m^-2 K^-2 and realizes continuous power output (over 12 h) at a constant temperature gradient, which is among the highest reported power output for TE converters and can be attributed to the combination of substantial increase in interfacial capacitive effect between ionogel and CPNF and an optimized electrical property of the CPNF. The work provides an effective strategy to overcome the limitations of both TEGs and ionic TE capacitors.