Ligand‐Regulated Amorphous Transition Layer in Cu@Ag Core‐Shell Composites for Boosting Electromagnetic Interference Shielding Performance

The electromagnetic interference (EMI) shielding performance of Cu@Ag core-shell composites is significantly determined by the silver shell morphology and core-shell interface properties. However, in-situ regulation of these features remains challenging due to the unclear formation mechanism for the Ag shell. Herein, we present a ligand-regulated synthesis in which ammonia is employed to precisely control the growth of the silver shell during liquid-phase reduction. Ammonia forms stable Ag(NH3)2+ complexes with silver ions, which modify the deposition kinetics. Such a shift transitions the coating process from rapid, anisotropic plating to controlled, uniform growth. Consequently, the morphology of the silver shell evolves from plate-like to particle-like structure, accompanied by the formation of an Ag-Cu transition layer at the core-shell boundary. These structural refinements dramatically reduce the electrical resistivity from 6.42 Ω·cm to 6.37 × 10- 4 Ω·cm. And the optimized structure exhibits superior EMI shielding effectiveness of 85.4 dB across 5.85-18 GHz range, with a peak radiation suppression of 26.8 dB. Moreover, the SE is further enhanced to 101.7 dB through a stratified stacking strategy. This work demonstrates ligand regulation as an effective strategy for enhancing EMI shielding performance.