Cost-effective graphite aerogel for high-temperature thermoelectrics: Synergizing ultra-high electrical conductivity and thermal insulation

High temperature exposure is commonly encountered in aerospace and industry, necessitating materials capable of providing both thermal insulation and thermal energy conversion. However, current thermoelectric aerogels often face dual challenges of constrained application temperatures (300–400 K) and prohibitively high costs due to substrate material limitations. In this study, a cost-effective graphite aerogel was fabricated using the directional freeze-drying method for integrated thermal insulation-thermoelectric applications across a wide temperature range. A pioneering Voronoi diagram-based electrical conductivity model featuring fractal lamellar structures was proposed with below 5% deviation between simulation and experimental data, which enables analysis of electrical transport properties under different densities of the lamellar structure, providing in-depth mechanism analysis of the interplay between microstructure and thermoelectric performance. By modulating the oriented lamellar skeletal structure, this aerogel achieved an efficient electrical carrier transportation of 48.28 S·cm⁻¹ and an effective suppression of thermal conductivity to 0.585 W·m⁻¹·K⁻¹ at 923 K. Remarkably, the aerogel exhibits a 2–3 orders of magnitude enhancement in cost-normalized electrical conductivity over current-generation thermoelectric aerogels. Due to the band degeneracy effect, the Seebeck coefficient shows a significant increase when the temperature exceeds 773 K and reaches 96.84 μV·K⁻¹ at 923 K. The hierarchically structured graphite aerogel exhibits exceptional high-temperature thermoelectric performance with a peak ZT value of 0.036, creating an innovative framework for high-temperature thermal management and energy conversion in extreme environments.