Covalent-bridged heterointerfaces via co-carbonization: A universal strategy for architecting 3D electron/phonon transport networks in dual-functional PI composites

Polyimide is widely used in electronics and communication due to its excellent overall properties. However, its inherently low electromagnetic interference (EMI) shielding effectiveness and poor thermal conductivity severely limit its further application in next-generation highly integrated, high-frequency, and high-power-density electronic devices. To address these issues, in this work, we develop a PI-based composite incorporating a three-dimensional carbon heterostructured network via a co-impregnation and co-carbonization strategy. This network—comprising MXene, graphene, and carbon fiber interconnected via covalent and graphitic-conjugated interfaces—effectively minimizes interfacial energy dissipation and facilitates simultaneous charge and phonon transport. By systematically optimizing the MXene/graphene mass ratio, dispersion concentration, and carbonization temperature, we achieve an ultrahigh EMI shielding effectiveness of 88.3 dB and an enhanced through-plane thermal conductivity of 1.54 W·m−1·K−1 at low filler loading. The composite also exhibits excellent thermal stability, with a 5% weight loss temperature up to 492 °C. This work presents a scalable and rational route for designing high-performance multifunctional composites through heterointerface and network topology control, effectively bridging the gap between thermal management and EMI shielding in applications such as 5G communications, wearable electronics, and high-power integrated circuits.