Lignin-Bonded Aramid Nanofiber/Graphene Composite Membranes for Tough and Stable Joule Heating

Flexible electric-heating materials (EHMs) with mechanical toughness and stability are in high demand in areas of portable heating elements; however, they are still hard to achieve. Here, strong and tough aramid nanofiber (ANF)/graphene composite membranes were fabricated with the help of interfacial lignin bonding through a noncovalent interaction-triggered “bridging” strategy. The as-prepared membranes (ANF-Lx-Gy) exhibited a maximum mechanical strength of ∼122.5 MPa, a maximum toughness of ∼377.2 MJ/m3, and also promising stabilities in commonly used solvents. Ascribing to the uniform distribution of graphene, the composite membranes presented enhanced conductivity (∼278 S/m) and demonstrated both high efficiency and stability for Joule heating performance (e.g., reaching ∼165 °C under an input voltage of 20 V within 5 s, eventually stabilizing at ∼200 °C, and remaining stable after 12 h of Joule heating). Besides the Joule heating application under low temperatures (e.g., joint worming below 100 °C), the stability of ANF-Lx-Gy also endowed them with favorable performances under high temperatures (e.g., deicing beyond 100 °C). Thus, this work paved a feasible way to develop ANF-based membranes that were strong and stable as flexible EHMs.