<scp> Fe ₃ O ₄ </scp> / <scp>CoNi</scp> ‐ <scp>LDH</scp> /Polypyrrole Ternary Composites for High‐Performance Electromagnetic Wave Absorption

ABSTRACT Effective electromagnetic wave (EMW) absorption can be realized by engineering heterostructures with carefully balanced chemical compositions and well‐defined spatial architectures. In this paper, Fe 3 O 4 /CoNi‐layered double hydroxide@Polypyrrole (Fe 3 O 4 /CoNi‐LDH@PPy) composites decorated with core‐shell structures are prepared by solvothermal and in situ polymerization methods. The combination of Fe 3 O 4 /CoNi‐LDH and PPy creates a dual‐loss mechanism, with the former capturing waves via magnetic and dielectric losses and the latter forming a conductive network to enhance overall performance. Due to their optimized structure, the Fe 3 O 4 /CoNi‐LDH@PPy composites display remarkable electromagnetic attenuation properties. Notably, the optimum reflection loss (RL min ) peaks at −54.59 dB (3.21 mm), and the effective absorption bandwidth (EAB) extends to 5.58 GHz even at a minimal thickness of 2.1 mm. The enhanced EMW absorption performance of these heterostructures originates from the synergistic interaction between magnetic loss and dielectric attenuation. This research presents a straightforward methodology for designing high‐efficiency electromagnetic absorbers that simultaneously meet the requirements of minimal thickness and reduced weight.