Flexible Ni-Fe-P/PPy@PI fiber paper-based composites with three-layer structure for 5 G electromagnetic shielding applications

•A facile and efficient strategy is proposed to prepare Ni-Fe-P/PPy paper-based composites.•This composites exhibited high temperature resistance, light weight and good flexibility.•The average EMI SE could reach 85 dB over the X-band (8–12.4 GHz).•The composites have low reflection and high absorption characteristics for electromagnetic waves. [Display omitted] In this paper, an ultra-thin and flexible paper-based composites with multi-layer structure characteristics are developed, which has low reflection and high absorption characteristics for electromagnetic interference (EMI). The composites use a high-temperature resistant polyimide (PI) fiber paper as a skeleton, followed by the successful growth of a layer of highly conductive polypyrrole (PPy) as a coating on the PI fiber by gas-phase polymerization. Then, a layer of Ni-Fe-P alloy was grown on the surface of the composite by a new, simple and economical palladium-free activated electroless plating process. With a thickness of only 0.19 mm, the effective shielding performance of the paper-based composites can reach over 85 dB. Bending experiments showed that the conductivity of Ni-Fe-P/PPy@PI fiber paper-based composites changed very little (retaining 92.0%) even after 200 deformation cycles. In addition, through mechanical and thermal stability testing, it is shown that the paper-based composites exhibit excellent mechanical properties and thermal stability, and can, therefore, be used in harsh environments. It is believed that such flexible paper-based EMI shielding composites have great potential in flexible intelligent equipment, communication equipment, aerospace, and other fields.