Flexible Conductive Polyimide Fiber/MXene Composite Film for Electromagnetic Interference Shielding and Joule Heating with Excellent Harsh Environment Tolerance.

The development of flexible MXene-based multifunctional composites is becoming a hot research area to achieve the application of conductive MXene in wearable electric instruments. Herein, a flexible conductive polyimide fiber (PIF)/MXene composite film with densely stacked "rebar-brick-cement" lamellar structure is fabricated using the simple vacuum filtration plus thermal imidization technique. A water-soluble polyimide precursor, poly(amic acid), is applied to act as a binder and dispersant to ensure the homogeneous dispersion of MXene and its good interfacial adhesion with PIF after thermal imidization, resulting in excellent mechanical robustness and high conductivity (3787.9 S/m). Owing to the reflection on the surface, absorption through conduction loss and interfacial/dipolar polarization loss inside the material, and the lamellar structure that is beneficial for multiple reflection and scattering between adjacent layers, the resultant PIF/MXene composite film exhibits a high electromagnetic interference (EMI) shielding effectiveness of 49.9 dB in the frequency range of 8.2-12.4 GHz. More importantly, its EMI shielding capacity can be well maintained in various harsh environments (e.g., extreme high/low temperature, acid/salt solution, and long-term cyclic bending), showing excellent stability and durability. Furthermore, it also presents fast, stable, and long-term durable Joule heating performances based on its stable and excellent conductivity, demonstrating good thermal deicing effects under actual conditions. Therefore, we believe that the flexible conductive PIF/MXene composite film with excellent conductivity and harsh environment tolerance possesses promising potential for electromagnetic wave protection and personal thermal management.