A super-stretchable and thermally stable hydrogel electrolyte for high performance supercapacitor with wide operation temperature

Flexible supercapacitors have attracted great attention owing to some advantages of flexibility, light weight and high-power output, and have displayed enormous potential in wearable electronic devices. However, the hydrogel electrolyte in flexible supercapacitors usually shows insufficient mechanical properties and low ionic conductivity under harsh environments, making it unsatisfactory for practical applications. Herein, a novel polyacrylamide/montmorillonite/ionic liquid-Li 2 SO 4 hydrogel electrolyte with wide temperature tolerance, high ionic conductivity and super-stretchable ability is prepared via facile thermally initiated radical polymerization. The layered montmorillonite can not only improve the thermal stability of the hydrogel, but also form a conductive channel to promote the rapid transport of ions. Moreover, the introduction of ionic liquid into the hydrogel can further increase the working temperature range. In consequence, the polyacrylamide/montmorillonite/ionic liquid-Li 2 SO 4 hydrogel electrolyte exhibits outstanding stretch ability (tensile strain over 1000%), high ionic conductivity (41.7 and 50.7 mS cm -1 at 25 °C and 40 °C, respectively). In addition, supercapacitor with the polyacrylamide/montmorillonite/ionic liquid-Li 2 SO 4 hydrogel electrolyte has good electrochemical property within the wide temperature tolerance from − 10–80 °C. • A novel hydrogel electrolyte (PAM/MMT/EMIMBF 4 -Li 2 SO 4 ) is prepared by easy method. • The hydrogel with porous structure has good twist, compress and stretch performance. • As electrolyte the hydrogel shows excellent ionic conductivity and thermal stability. • Supercapacitor with the hydrogel electrolyte possesses good electrochemical properties.