A Nacre‐Mimetic Mullite Nanofiber Aerogel Paper Achieving High‐Voltage Electrical and Thermal Insulation via Self‐Templated Assembly

Simultaneously achieving high‐voltage electrical insulation and high‐temperature tolerance in a single lightweight material remains a formidable challenge due to the intrinsic conflict between dielectric strength and thermal stability. Here, we solve this problem by constructing a flexible, nacre‐mimetic mullite nanofiber aerogel paper through a self‐templated electrospinning strategy. In this design, functionalized mica nanosheets serve as dielectric barriers uniformly embedded within a mullite nanofiber framework, forming a brick‐and‐mortar architecture. This structure not only creates an extended tortuous path to suppress electron avalanche breakdown but also establishes a double‐network bandgap that inhibits charge transport and segmental chain motion. The aerogel paper thus achieves an exceptional electrical resistivity of 6.5 × 10 14 Ω·cm while maintaining stable dielectric performance above 500°C. Moreover, by grafting low‐surface‐energy ormosil directly into the precursor sol, we circumvent the pore‐clogging and hydration issues inherent to post‐synthesis treatments, endowing the aerogel paper with super‐hydrophobicity. This combination of ultralight weight, high‐temperature dielectric stability, and environmental durability represents a paradigm shift in material design for next‐generation miniaturized high‐power electronics.