Lignin Crosslinked Ultrastable ANF‐CNT Films for Photo‐Thermal‐Electric Conversion and Joule Heating

Aramid nanofibers (ANF) with excellent toughness and stability are promising candidates as flexible matrix for fabrication of wearable devices, nevertheless, which still suffer from the drawback of surface activation. In this work, the lignin that possesses structural affinity with ANF is applied to activate ANF, which further composites with carbon nanotubes (CNT) through vacuum filtration and subsequent thermal-crosslinking processes. Ascribing to the multiply interfacial lignin binding (i.e., noncovalent hydrogen bonding and π-π stacking, and covalent C─C and C─O─C bonds), the resulted films (AL_xC_y (TC)) exhibit simultaneously enhanced mechanical properties (the tensile strength of ∼88.6 MPa and toughness of ∼77.2 MJ m^-3), stabilities (e.g., in commonly used solvents, and under -20°C-100°C and deformation) and conductivity (∼148.2 S m^-1). The synergy of CNT and lignin endows composite films with superior photo-thermal-electric (∼62°C and 150 mV under 1000 W m^-2 of illumination within 10 s) conversion capabilities. Moreover, the ultrastable AL_xC_y (TC) also demonstrates favorable Joule heating properties (∼105°C under 25 V) that can be applied in chair warming and ice melting. Thus, this work paves a green and efficient way to optimize the interfacial compatibility between ANF and functional components, and build composite films for durable energy management.