Flexible, all-hydrogel supercapacitor with self-healing ability

Supercapacitors with multiple functions, such as high capacitance, high flexibility and self-healing properties, are capturing more and more attention in portable and wearable electronics. Herein, an all-hydrogel supercapacitor with multiple functions was fabricated, by sandwiching the polyaniline (PANI)-polyvinyl alcohol (PVA) hydrogel electrodes with a PVA-based hydrogel electrolyte which both contain the same healable and tough hydrogel matrix. The special efficient assembly between of PANI and PVA enables the hydrogel electrodes with superior electric conductivity of 136 S m−1 and large specific capacitance of 351 F g−1, as well as the great robustness and self-healing ability. The all-hydrogel supercapacitor exhibited a tensile strength of 2.21 MPa, a breaking elongation of 633%, a capacitance of 78.5 F g−1, and an energy density of 7.8 Wh kg−1. Due to its great toughness and flexibility, the supercapacitor could maintain stable energy output even after being subjected to various deformations (e. g., stretching, compressing, bending and even pinning). In addition, the severed supercapacitor could heal itself within 4 h at 70 °C, and the healed supercapacitor could restore good electrochemical properties with a healing efficiency of 49.8%. These highlighted properties enable this supercapacitor as a promising smart storage device for wearable application.