Dual ions-mediated electrochemical polarization enables dynamic electromagnetic wave response in flexible device

A dual-ion (H + /Cl − ) electrochemical polarization strategy dynamically tunes EMW shielding in flexible CNTs@PANI composites. • Dual-ion intercalation restructures PANI to optimize its band gap, sheet resistance, and reflective EMW shielding. • Uneven ion accumulation enlarges dipole moment and dielectric constant, significantly boosting EMW absorption shielding efficiency. • Synergistic reflection-absorption modulation achieves an ultrahigh specific shielding effectiveness variation of 289.44 dB·mm −1 . • A flexible sandwich device offers tunable X-band EMW shielding (26.29–42.06 dB) and robust bending/cycling stability. Dynamic manipulation of electromagnetic waves (EMWs) represents an indispensable cornerstone for next-generation intelligent stealth and adaptive communication systems. Nevertheless, the practical implementation of state-of-the-art electromagnetic materials remains severely constrained by insufficient modulation capabilities arising from single regulatory mechanisms, along with compromised operational flexibility and reliability. Herein, we report a dual-ion-mediated electrochemical polarization strategy in a flexible carbon nanotube@polyaniline (CNTs@PANI)-based device, which enables precise dynamic regulation of EMWs via the synergistic modulation of electromagnetic reflection and absorption. In-situ structural characterizations coupled with theoretical simulations demonstrate that electric-field-triggered H + /Cl − dual-ion intercalation drives the structural rearrangement of PANI from a non-polarized quinoid state to a polarized benzenoid structure. This transformation increases the content of protonated imine groups from 33.01% to 60.97%, narrows the band gap from 2.62 eV to 0.99 eV, and lowers the sheet resistance by 82.4% (from 47.99 to 8.43 Ω·sq. −1 ), thereby tailoring the EMW reflection shielding effectiveness (SE R ) from 4.71 dB to 8.84 dB. Furthermore, the asymmetric electrostatic potential distribution induced by H + /Cl − dual-ion intercalation and accumulation in PANI backbone amplifies the dipole moment by 118% (from 4.02 to 8.77 Debye), generating a pronounced dielectric polarization effect accompanied by maximum enhancement ratios of 172% and 6300% for the real (ε’) and imaginary (ε”) parts of the permittivity, respectively, which boosts the absorption shielding effectiveness (SE A ) from 11.12 to 17.75 dB. Consequently, the synergistic modulation of reflection and absorption contributes to thickness-normalized specific shielding effectiveness variation amplitude (ΔSSE) of 289.44 dB·mm −1 for the CNTs@PANI within the X-band (8.2–12.4 GHz), surpassing previously reported systems. This work establishes a novel paradigm for designing high-performance adaptive EMW protection systems through dual-ion electrochemical engineering.