Asymmetric multilayer structure enabling absorption-dominant and ultrahigh-efficiency electromagnetic shielding

Achieving simultaneously high-efficiency shielding effectiveness (SE) and ultralow reflection coefficient remains challenging for next-generation electromagnetic interference (EMI) shielding materials. In this work, we report rationally designed three-layer architectures comprising a low-reflection polyvinylidene fluoride (PVDF) foam layer, a carbon nanotube (CNT)/flaky Fe/PVDF composite foam as the absorption layer with tuned impedance matching and attenuation characteristics, and a thin graphene film as the reflective shielding layer to promote reflection–reabsorption cycles. Gradient and asymmetric sandwich configurations are designed based on intrinsic reflectance (R_η) considerations. With a total thickness of ∼2 mm, the optimized multilayer structures achieve an ultrahigh EMI SE of up to 118 dB. Through systematic variation of layer sequence and thickness, distinct attenuation behaviors are revealed. Gradient structures enable progressive impedance transition and reduced overall reflection, achieving a low average reflection coefficient of 0.052 in the X-band. In contrast, asymmetric sandwich architectures enhance internal dissipation through multiple reflections and phase-dependent interference, yielding ultralow reflection at selected frequencies with a minimum reflection coefficient as low as 0.0001 and a corresponding ultrahigh absorption-to-reflection ratio (A/R) of 9962. Transmission-line theoretical predictions and CST simulations agree closely with experimental results, indicating that the reflection behavior is predominantly governed by impedance recursion and thickness-dependent phase interference, with higher-order microstructural effects implicitly accounted for through effective electromagnetic parameters. This work establishes a fundamental framework for rationally designing absorption-dominant multilayer EMI shielding systems through coordinated regulation of electromagnetic properties, impedance characteristics, and phase-controlled thickness optimization.