High-performance n-type flexible inorganic thermoelectric aerogel for energy harvesting

Despite their promise as lightweight, ultralow-thermal-conductivity thermoelectric (TE) materials, aerogels have been largely limited to p-type organic or carbon-based systems with modest zT < 0.1 at 300 kelvin. Here, we propose a stepwise synthesis strategy that yields the first inorganic aerogel exhibiting state-of-the-art n-type TE performance. Optimized aerogels with 95% porosity exhibit a high power factor of 34.8 microwatts per meter per square kelvin and an ultralow thermal conductivity of 0.061 microwatts per meter per kelvin, resulting in zT values of 0.17 at 300 kelvin and 0.24 at 383 kelvin. A vertical TE generator prototype with six TE-aerogel legs achieves a gravimetric output power of 76 microwatts per gram under a ΔT of ~60 kelvin. To address brittleness, a polyimide-encapsulated aerogel with bioinspired architecture was developed, achieving a high compressive strength to 1.4 kilopascals while maintaining excellent TE performance. This work establishes a generalizable method for designing high-performance flexible inorganic aerogels, opening more possibilities for lightweight wearable energy harvesting technologies.