materials and stretchable substrates. [15] But these substrates are generally electrochemically nonactive elastomers, which would occupy a significant volume and mass in SSCs, and reduce specific capacitance and energy density of SSCs. In addition, due to the mismatch of Young's modulus of soft substrates and rigid electroactive materials, inevitable dislocation occurs at the interface upon a large deformation, which could damage the integrity and hence the electrochemical performance of SSCs. [16] On the other hand, specific structures can extend flexibility to stretchability. For instance, wavy structure [12][13][14] resembling spongy structure, also called winkled [17,18] or buckled structure, [19,20] can be used for rigid materials to achieve a certain level of stretchability, such as single-crystal Si, [21] graphene film, [17,19] and interwoven carbon nanotube. [18,20] Multistep processing is typically required to obtain these wavy structures, such as exploiting and removing buckled templates, [17] prestraining, and releasing elastic substrates. [18] Some fiber-shaped electroactive materials can be woven into overtwisted yarn [22][23][24][25] to achieve a certain level of stretchability. Besides these strategies, there are rarely any reports of stretchable supercapacitors without using elastic substrates or complicate fabrication, like wavy or yarn structures.Carbon-based materials [26,27] are often chosen as the electroactive materials of SSCs, while the specific capacitance of obtained SSC devices is limited by the low theoretical capacitance of carbon-based materials. In contrast, conducting polymers show a much higher specific capacitance, and are often composite with carbon materials to achieve enhanced capacitance. [22,[28][29][30] Recently, conductive polymer-based hydrogels (CPHs) have been developed for flexible supercapacitors, and these CPH-based flexible supercapacitors show enhanced specific capacitance and cycling stability. [31][32][33][34] However, the conductivity of most of current CPHs is typically in the range of 10 −4 -10 −1 S cm −1 , [35,36] which is not sufficient, and conductive supports are required as current collector to assemble electrodes. Since these conductive supports such as carbon cloth or metal mesh are not stretchable, the obtained CPH-based flexible supercapacitors are not stretchable. To bypass the usage of conductive supports, the development 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 stre...