Ionic devices find applications such as flexible electronics and biomedicines and function by exploiting hybrid circuits of mobile ions and electrons. However, the poor interfacial compatibility of hard electronic conductors with soft ionic conductors in ionic devices leads to low deformability, sensitivity, electromechanical responses, and stability. Herein, an interpenetrating interface between silicone-modified polyurethane/carbon nanotube electronic conductors and ionoelastomers in an ionic device using in situ polymerization is fabricated. A robust interpenetrating electronic/ionic conductor interface is realized through molecular chain entanglement and molecular forces (such as ion-dipole interactions and H-bonds), effectively enhancing the bonding strength and contact area between the components and resulting in an excellent flexibility, stability, and device performance. The electroadhesive prepared based on this strategy exhibits a superrobust shear strength of 317 kPa under a reduced voltage input of -4 V, and the diode and the transistor can undergo arbitrary deformation while maintaining the semiconductor device characteristics, including rectification and switching. In addition, electromechanical transducers exhibit sensitive electrical responses to various deformation signals. This solution to the interfacial compatibility problems of electronic and ionic conductors holds promise for the development of multifunctional ionic devices.