Hollow Structured‐Controllable Polyimide Nanofibers with Extreme Conditions Tolerance for Efficient Thermal Insulation

The rational use of efficient thermal insulation materials is one of the effective strategies for energy management. However, existing thermal insulation materials often exhibit poor stability, suboptimal thermal insulation performance, and weak mechanical properties in some extreme environments. Herein, this work develops an easy and scalable strategy for creating hollow polyimide (PI) nanofibers through coaxial electrospinning and high‐temperature template removal technology, in which the internal hollow structure is precisely controlled. A large amount of air is filled in the hollow structure within the nanofibers and the voids between the nanofibers, giving PI nanofibers low density (23.3 mg cm −3 ) and high porosity (98.2%). This characteristic also effectively suppresses the heat transfer of PI nanofibers, resulting in an ultralow thermal conductivity (20.6 mW m −1 K −1 ). Meanwhile, PI nanofibers also exhibit excellent mechanical properties with a stress and strain of 5.52 MPa and 62.7%, respectively. In addition, compared to other commercial thermal insulation materials, PI nanofibers demonstrate superior extreme temperature tolerance (from −196 to 350 °C) and flame retardancy (limit oxygen index of 30.8%). Given these advantages, this work provides inspiration for the structural design of nanofiber materials with efficient thermal insulation.