Stretchable all-in-one supercapacitor enabled by poly(ethylene glycol)-based hydrogel electrolyte with low-temperature tolerance

Hydrogel electrolytes are crucial components of stretchable energy storage devices due to their flexibility and excellent ion transport ability. However, most hydrogels lose their stretchability in subzero-temperature environments. Herein, a stretchable all-in-one supercapacitor that can work at low temperatures was developed by designing an anti-freezing polyacrylic acid (PAA) hydrogel incorporated with polyethylene glycol (PEG)/H2O solvent. PEG endowed the hydrogel with anti-freezing property while avoiding the instability of low-molecular organic solvents. The all-in-one supercapacitor was prepared through the in-situ polymerization and deposition of polyaniline on the faces of the anti-freezing hydrogel electrolyte. The obtained supercapacitor exhibited high capacitive performance, good stretchable capacity, and excellent cycling stability. Moreover, benefiting from the outstanding low-temperature tolerance capacity, the all-in-one supercapacitor can maintain an area specific capacitance of over 63.1% even at −25 °C. This work presents an innovative polymer-solvent system for developing an anti-freezing stretchable all-in-one configured supercapacitor for use as a portable energy storage device in wearable electronics.