Ion Mobility Engineering for Balanced Impedance Matching and Electromagnetic Loss

ABSTRACT Suppressing ionic motion in ionogels for the fabrication of unprecedented EMW absorbers remains an unexplored frontier, as researchers have predominantly focused on facilitating rather than inhibiting ion transport. Herein, a rational double‐network design strategy is developed to synthesize an ion motion‐suppressed ionogel with record‐high EMW absorption performance (minimum reflection loss −63.45 dB and 6.19 GHz bandwidth) that surpasses most ionogel absorbers. The double‐network is constructed via the entangled assembly of polymethyl methacrylate and poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS) in 1‐ethyl‐3‐methylimidazolium methanesulfonate ionic liquids. Thanks to strong electrostatic interactions, ion motion is restrained by the PAMPS network, balancing impedance matching and dielectric loss under EM fields. The resultant ionogels demonstrate a minimum reflection loss of ‐63.45 dB at 1.8 mm and a broad effective absorption bandwidth of 6.19 GHz (fully covering the Ku‐band), both setting up new EMW absorption benchmarks among ionogels and their hybrids. Unlike emerging approaches that promote ionic conduction for loss, here we suppress ion mobility to optimize impedance matching, a paradigm shift in ionogel design. In essence, this work introduces a strategy to design high‐performance, multifunctional ionogels, paving the way for next‐generation flexible EMW absorbers in 5G/6G communications and wearable electronics.