Highly electroconductive and mechanically strong TiCT/cellulose nanofiber composite paper with gradient structure for efficient electromagnetic interference shielding.

The remarkable electrical conductivity of TiCT endows it with significant potentiality in electromagnetic interference (EMI) shielding. However, its poor mechanical properties constrain its further application. Presently, the principal approach to improve the mechanical properties of TiCT is to introduce a large quantity of flexible polymers, which leads to a sharp decrease in conductivity and thereby impacts EMI shielding performance. Herein, a flexible TiCT/cellulose nanofiber composite paper with a gradient structure (GS-TCCP) was fabricated by utilizing the fact that the total resistance is lower than the partial resistance in parallel circuits. The highly conductive thin layers are connected in parallel with the mechanically strong thick layers. This not only maintains the high conductivity but also promotes the enhancement of the mechanical properties. Moreover, the unique interlayer reflection and intralayer absorption mechanisms of the gradient structure also promote the further enhancement of EMI shielding effectiveness (SE). The GS-TCCP (38.33 wt% TiCT, thickness of ∼75 μm) not only exhibits a high conductivity of ∼13110 S/m and strong mechanical properties (with a tensile strength of ∼78.2 MPa and a toughness of ∼4.019 MJ/m), but also has an EMI SE of 46.8 dB in the X-band (8.2-12.4 GHz). In addition, its EMI efficiency reaches up to 99.998%, which is comparable to that of the homogeneous TiCT/CNF composite paper with 50 wt% TiCT and superior to most of the reported TiCT-based thin film composites. The balance among conductivity, EMI shielding performance, and mechanical properties makes it have broad application prospects in fields such as EMI shielding, flexible sensing, and flexible electronic components.