Electrochemically‐Switched Microwave Response of MXene in Organic Electrolyte

The increasingly complex electromagnetic (EM) environment necessitates advanced electrically controllable electromagnetic interference (EMI) shielding materials that can adapt to varying EM conditions. This study develops a flexible electrochemically tunable EMI shielding device based on ultrathin Ti3C2Tx MXene films, exhibiting reversible shielding effectiveness (SE) modulation from 18.9 to 26.2 dB in X band at 0.1 and −1.5 V. Unlike the previously reported mechanism relying on interlayer spacing adjustments, the work leverages transformations of charging state and surface chemistry for tunability during the electrochemical process. The Ti3C2Tx flake size is also evidenced to play a crucial role, with smaller flakes offering higher absorption modulation despite lower SE modulation, enabling the device with high designability. When integrated with Salisbury screen structure, the device achieves adjustable absorption from 93.560% at 0.1 V to 99.996% at −1 V, showing a tunable reflection suppression ratio up to 32 dB with an effective bandwidth of 4.2 GHz. Additionally, incorporating resonant cavity structure enables absorption‐dominated (over 90%) microwave‐responsive switching at 0.1 and −1.5 V. This work highlights significant potential of adaptive EMI shielding materials for applications in smart electronic protection, EM switch, and radar camouflage. Flexible electrochemically adjustable electromagnetic interference shielding devices are developed based on the tunable charging states and surface chemistry of Ti3C2Tx MXene. By integrating the electromagnetic switching device with Salisbury screen and double‐layer resonant cavity structure, dynamic camouflage and wave‐absorbing switch are achieved, respectively. This versatile device holds promise for future advanced electromagnetic protection, stealth, camouflage, and other applications.