A Single Robust Hydrogel Film Based Integrated Flexible Supercapacitor

Integrated configuration can greatly improve the stability of an energy-storage device in a large or repeated mechanical deformation process, but there is little attention paid to develop this conceptual energy-storage device. Here, we successfully design two embedded polypyrrole (PPy) layers as electrodes and a boron cross-linked PVA(poly(vinyl alcohol))/KCl hydrogel film as electrolyte to construct an integrated electrode–electrolyte–electrode flexible supercapacitor (so-called all-in-one supercapacitor). The boron cross-linked PVA/KCl hydrogel film (B-PVA/KCl) is prepared by simple physical and chemical cross-linking methods. Then, the conducting PPy is embedded in the B-PVA/KCl film by in situ growth to form a PPy/B-PVA/KCl composite film, which shows superior toughness and strength when it undergo large deformations, such as stretch, twist and compression. The integrated flexible supercapacitor can obtain a large areal capacitance of 224 mF cm–2 and a remarkable energy density of 20 μWh cm–2. Furthermore, such device exhibits excellent electrochemical stability under various bending angles (0°, 90°, and 180°) or 500 bending-releasing cycles, which due to the integrated electrode–electrolyte–electrode configuration can avoid the fall-off of electrode materials from the substrates and overcome the relative displacement between electrode and electrolyte layers during the consecutive bending cycles.