Strong and Stretchable Polypyrrole Hydrogels with Biphase Microstructure as Electrodes for Substrate‐Free Stretchable Supercapacitors

Abstract The development of stretchable supercapacitors (SSCs) is heading to compact and robust devices with higher capacitance and simpler preparation process. Herein, a new strategy is reported to prepare a highly stretchable and conductive polypyrrole hydrogel with a unique biphase microstructure (loose phase and dense phase), which is formed by the supramolecular assembly of polypyrrole (PPy), poly(vinyl alcohol), and anionic micelles. The loose phase enables the PPy hydrogel large stretchability (elongation at a break of 500%) and good electrochemical capacitive behavior, while the dense phase enables the PPy hydrogel high tensile strength (2 MPa) and good conductivity (0.8 S cm −1 ). Without using any substrate, the SSC made of this polypyrrole hydrogel provides an areal capacitance of 950 mF cm −2 at a current density of 1.6 mA cm −2 , exceeding most of reported SSCs. This SSC can withstand repeated deformation and retain 81% capacitance after 500 stretching–releasing cycles. Besides, at subzero temperature down to −20 °C, this SSC can still retain its good stretchability and capacitance. The combination of high areal capacitance, good stretchability, and high retention of capacitance under various circumstances enables the polypyrrole hydrogel–based SSC an economical and robust SSC for stretchable electronics.