Stretchable, Phase‐Transformable Ionogels with Reversible Ionic Conductor–Insulator Transition

Abstract Stretchable iontronics with reversible conductor–insulator transitions are attracting great interest due to their promising applications in various fields of flexible electronics. However, effective conductivity switching of the ion conductors is still challenging. Here, a phase‐transformable ionogel (PTIG) that shows a reversible conductor–insulator transition with a very sharp change in bulk ionic conductivity (≈10⁷ times) at a mild transition temperature of −15 °C is introduced. Moreover, this unique material shows good stretchability (840%), high transparency (97% transmittance in the visible range), and good stability. The ionogel material is used to prepare a long‐storage capacitor, which demonstrates good performance. Hence, the new PTIG has the potential for application in the development of flexible iontronics.