Flexible all-in-one supercapacitors enabled by self-healing and anti-freezing polymer hydrogel electrolyte

The functions of polymer hydrogel electrolyte (PHE) have been limited by external force fracture and freezing at zero temperature. Herein, the self-healing and anti-freezing polyvinyl alcohol (PVA)/glycerin (Gly)/sulfuric acid (H2SO4) (PGS) hydrogel electrolyte has been prepared by freezing-thawing (F-T) cycles. Based on the synergistic enhancement of hydrogen bonds between Gly and PVA, the PGS hydrogel shows remarkable self-healing properties (the ionic conductivity reaches 34.4 mS cm−1 after 10 cutting/healing (CH) cycles) and anti-freezing properties (the ionic conductivity reaches 17.1 mS cm−1 at −40 °C). All-in-one supercapacitors (SCS) have been assembled by in-situ polymerization of aniline (ANI) as electrode on the surface of PGS hydrogel. The SCs exhibit considerable specific capacitance of 476 mF cm−2 at current density of 0.2 mA cm−2, excellent power density (100 μW cm−2) and energy density (33 μWh cm−2), remarkable self-healing performance (48.5 % specific capacitance retention rate after 10 CH cycles) and outstanding anti-freezing properties (56.3 % capacitance retention rate at −20 °C). The self-healing and anti-freezing PGS hydrogel electrolyte displays broad application prospects in the field of flexible energy storage devices.