Micro-nano hierarchical SPBID/AlN composites breaking the thermal conductivity-insulation trade-off

Nanoporous structures have demonstrated remarkable potential for enhancing breakdown strength by suppressing internal gas ionization, enabling the development of ultra-insulating materials. However, their inherent gas-solid interfaces induce severe phonon scattering, posing a challenge for the simultaneous improvement of electrical insulation and thermal conductivity. Herein, we report a cross-scale structural design strategy that integrates multiple functions, a starch-based polyorganosiloxane biocomposite insulating dielectric/aluminum nitride (SPBID/AlN) composites is fabricated, featuring a micro–nano scale nested architecture. The microscale AlN framework provides thermal conductivity while the nanoscale SPBID ensures superior electrical insulation, effectively resolving the trade-off between high breakdown strength and high thermal conductivity. SPBID/AlN exhibits lightweight, high mechanical strength, low relative permittivity, and biodegradability, especially, promising potential for combining with atmospheric CO 2 to form high-performance and carbon-sequestering insulating material. Specifically, when SPBID/AlN integrates with insulating gases (CO 2 , SF 6 ), the breakdown strength is significantly enhanced by 711.91 % and 270.42 % compared to the pure gases, respectively. Furthermore, SPBID/AlN achieves high thermal conductivity (2.51 W/(m·K)), representing 15.68-fold and 75.06-fold improvements compared to epoxy (0.16 W/(m·K)) and nanoporous SPBID (0.033 W/(m·K)), respectively. The continuous thermal pathways in AlN facilitate efficient heat transport. Overall, this study presents a novel strategy for the development of future high-performance, lightweight, and eco-friendly power equipment and electronic devices.