Polyzwitterionic hydrogel electrolytes via ultrafast autocatalytic gelation process for flexible Zn-Ion hybrid supercapacitors

Hydrogel electrolytes with high intrinsic toughness and ionic conductivity are considered essential for realising flexible energy storage. Polyzwitterionic hydrogel electrolytes typically exhibit excellent ionic transference number and conductivity because of their distinct rapid anionic and cationic channels, thereby achieving superior ionic transport kinetics. This paper presents an ultrafast autocatalytic gelation process, which can produce a self-adhesive hydrogel electrolyte (PAD@SC) via copolymerization of vinyl monomer acrylic acid and zwitterionic monomer sulfobetaine in a time scale of seconds instead of hours at room temperature (approximately 20 °C). The incorporation of bio-based functional enhancement components, namely, sodium lignosulfonate and nanocellulose, into the hydrogel precursor solution facilitated the reconstruction of noncovalent hydrogen bond networks within the hydrogel, resulting in enhanced mechanical properties. Moreover, the PAD@SC hydrogel electrolyte prepared using this autocatalytic system can effectively inhibit the growth of Zn dendrites to realize a stable Zn anode. The assembled PAD@SC-based flexible Zn-ion capacitors possess high specific capacitance (85.4 mAh g−1), rate performance, and cycling stability (10000 cycles at 5 A g−1), indicating remarkable potential for practical application in flexible power supplies.