A self-adhesive, self-healing zwitterionic hydrogel electrolyte for high-voltage zinc-ion hybrid supercapacitors

With the widespread application of portable electronic devices, high-performance supercapacitors have attracted enormous interest. Nevertheless, the previously reported supercapacitors typically suffer from a few disadvantages, such as the low energy density, irreversible breakage and poor interface combination between electrolyte and electrodes, restricting the development of high-performance supercapacitors. Herein, the betaine-based zwitterionic hydrogel electrolyte with excellent self-healing properties, anti-drying ability and mechanical flexibility was prepared for zinc-ion hybrid supercapacitor (ZIHS). Betaine enhanced the adhesion of zwitterionic hydrogel electrolytes, which promoted the interface bonding between electrolyte and electrode. Impressively, the ZIHS based on zwitterionic hydrogel electrolytes exhibited a wide electrochemical stability window of 2.2 V and a high energy density of 237.34 mAh/g. In addition, the ZIHS based on zwitterionic hydrogels possessed great self-healing ability, the self-healing efficiency achieved 88.3 % of the initial state after five cutting-healing cycles. This research will supply an effective strategy for the design of hydrogel-based supercapacitors with wide voltage windows, high energy density and reusability.