An Intrinsically Antifreezing and Self-Adhesive Hydrogel Electrolyte for Flexible Zinc Ion Hybrid Capacitors

Abstract

Flexible zinc ion hybrid capacitors (ZIHCs) have attracted extensive research interest by virtue of their high safety and low cost. However, their low-temperature application remains limited due to the freeze of hydrogel electrolytes. Herein, we prepared an intrinsiclly antifreezing amphiphilic copolymer hydrogel based on hydrophilic monomer 2-Hydroxyethyl acrylate and hydrophobic monomer 1H, 1H, 2H, 2H perfluorooctyl methacrylate. Thanks to the hydrogen bond destruction effect of the hydrophilic units and the nano-confinement effect of the hydrophobic units, the hydrogel exhibited a freezing point as low as −30 °C, which was significantly lower than that of hydrogel prepared using pure hydrophilic monomers. In addition, the hydrogel also showed excellent adhesion performance, which contributed to the assembly of device and prevented layer-to-layer slippage during the device use. By soaking the hydrogel in Zn(ClO₄)₂ solution to serve as the electrolyte of the ZIHC, the device achieved excellent electrochemical performance at −50 °C. This work provides a new path for the design of antifreeze hydrogel electrolytes for ZIHCs.