An Ultrastretchable and Highly Conductive Hydrogel Electrolyte for All‐in‐One Flexible Supercapacitor With Extreme Tensile Resistance

Stretchability is a crucial property of flexible all‐in‐one supercapacitors. This work reports a novel hydrogel electrolyte, polyacrylamide‐divinylbenzene‐Li 2 SO 4 (PAM‐DVB‐Li) synthesized by using a strategy of combining hydrophobic nodes and hydrophilic networks as well as a method of dispersing hydrophobic DVB crosslinker to acrylamide monomer/Li 2 SO 4 aqueous solution by micelles and followed γ‐radiation induced polymerization and crosslinking. The resultant PAM‐DVB‐Li hydrogel electrolyte possesses excellent mechanical properties with 5627 ± 241% stretchability and high ionic conductivity of 53 ± 3 mS cm −1 . By in situ polymerization of conducting polyaniline (PANI) on the PAM‐DVB‐Li hydrogel electrolyte, a novel all‐in‐one supercapacitor, PAM‐DVB‐Li/PANI, with highly integrated structure is prepared further. Benefiting from the excellent properties of hydrogel electrolyte and the all‐in‐one structure, the device exhibits a high specific capacitance of 469 mF cm −2 at 0.5 mA cm −2 , good cyclic stability, safety, and deformation damage resistance. More importantly, the device demonstrates a superior tensile resistance (working normally under no more than 300% strain, capacitance stability in 1000 cycles of 1000% stretching and 10 cycles of 3000% stretching) far beyond that of other all‐in‐one supercapacitors. This work proposes a novel strategy to construct tensile‐resistant all‐in‐one flexible supercapacitors that can be used as an energy storage device for stretchable electronic devices.