Electrochemically Cation‐Induced Three‐Phase Conversion for Consecutively Tunable Electromagnetic Wave Response

Abstract Tunable electromagnetic wave responses are increasingly attracting attention in the realm of integrated electronics. However, the modulation flexibility and reliability are limited in the current electromagnetic shielding materials. In this study, a device with a sandwich‐structured configuration of metal mesh@H x WO 3 /H 2 SO 4 /hollow graphite is designed to enable dynamic response and precise control for electromagnetic waves (EMWs). In‐situ characterizations and theoretical simulation revealed that the electrochemically controlled cation intercalation preferentially triggers the reversible conversion of H x WO 3 from the monoclinic phase (M‐phase) to the tetragonal phase (T‐phase), and subsequently to the cubic phase (C‐phase) by voltage management, which leads to a successive increase in valence electrons and enhancement in conductivity for precisely modulating reflection shielding efficiency of the incident EMWs. Furthermore, the intercalation and accumulation of the external cations produce a mass of dipoles in the crystal H x WO 3 host structure, which further enhances the dielectric performances of materials and the dissipation capability of incident EMWs, and thus improves the electromagnetic absorption shielding effectiveness. Consequently, the outstanding modulation capability Δ: 42.36 dB) and consecutively tunable intensity (from 10.98 to 53.34 dB) of electromagnetic shielding effectiveness is realized, which provides a more remarkable technology for adapting to demanding environments through the dynamical regulation of EMWs.