Highly electroconductive and mechanically strong Ti₃C₂T_x/cellulose nanofiber composite paper with gradient structure...

The remarkable electrical conductivity of Ti₃C₂T_x 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 Ti₃C₂T_x 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 Ti₃C₂T_x/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% Ti₃C₂T_x, 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/m³), 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 Ti₃C₂T_x/CNF composite paper with 50 wt% Ti₃C₂T_x and superior to most of the reported Ti₃C₂T_x-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.