Capillary-Driven Densification of Bilayer Ultrathin Carbon Fiber Composite Paper for EMI Shielding and Electrothermal Conversion

Addressing the demand for miniaturization and multifunctionality in next-generation EMI shielding materials, the attenuation of EMI shielding effectiveness during the thinning of carbon fiber-based composites must be minimized to expand their applicability. Herein, a simple, capillary force-driven molding strategy is developed to fabricate an ultrathin bilayer cellulose nanofiber (CNF)/short carbon fiber (SCF)/reduced graphene oxide (rGO) composite paper (L-CSG). This approach sequentially fills the SCF network with CNF and rGO/CNF, forming a micrometer-scale bilayer structure synergizing with a nacre-like nanostructure constructed via CNF-rGO hydrogen bonding. Owing to this multiscale structure design, the resulting L-CSG paper (94 μm thick) exhibits superior comprehensive properties: high electrical conductivity (1014.5 S/m), excellent EMI SE (31.9 dB), and considerable tensile strength (30.88 MPa). Notably, its specific EMI SE (339.79 dB/mm) surpasses that of most reported flexible carbon fiber-based shielding materials. Furthermore, the integrated conductive network within this structure endows L-CSG with a superior electrothermal conversion performance. The straightforward molding strategy and the multiscale structure design enable the fabrication of an ultrathin carbon fiber composite paper. Combining superior comprehensive performance with multifunctional integration, L-CSG demonstrates significant application potential in fields such as transoceanic shipping, aerospace, 5G technology, and polar scientific exploration.