Abstract

Abstract Highly efficient electromagnetic wave (EMW)‐absorbing multicomposites can be fabricated by constructing particular structures using suitable components. Expanded graphite (EG) has a 3D, low‐density porous structure; however, it suffers from poor impedance matching and EMW absorption properties. Based on this information, in the present study, NiCo 2 S 4 components with different morphologies are successfully loaded onto a 3D EG surface using a facile microwave solvothermal method to achieve a synergistic effect between the different components. The NiCo 2 S 4 content is adjusted to alter the compositional morphology and electromagnetic parameters of the composites to achieve impedance‐matching and obtain excellent EMW absorption properties. The heterogeneous interface between EG and NiCo 2 S 4 induces an inhomogeneous spatial charge distribution and enhances interfacial polarization. The defects in the material and oxygen‐containing groups induce dipole polarization, which enhances the polarization‐relaxation process of the composites. The 3D porous heterostructure of the “Fibonacci cauliflower”‐shaped NiCo 2 S 4 /EG composites results in an optimal reflection loss of −64.93 dB at a filler rate of only 14 wt.%. Analysis of the synergistic conduction loss and polarization loss mechanisms in carbon‐based materials with heterogeneous interfaces has led to the development of excellent EMW absorption materials.