Janus POSS-based hydrogel electrolytes with high-ionic conductivity and low-temperature-resistance for all-in-one flexible supercapacitors

Abstract

With the continuous advancement of smart wearable devices and flexible electronics, flexible hydrogel supercapacitors are increasingly becoming one of the ideal wearable energy storage systems due to their high water content and excellent mechanical flexibility. However, it remains a challenge for flexible hydrogel supercapacitors to maintain sufficient flexibility and satisfactory electrochemical performance at sub-zero temperatures. In this study, we developed an innovative hydrogel electrolyte by integrating 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) into the hydrogel network structure of water-soluble Janus-type polyhedral oligosiloxane (AS-POSS)-based hydrogel. This strategic integration significantly enhanced the ionic transport efficiency and mechanical properties of the hydrogel. Our findings revealed that the modified hydrogel electrolyte exhibited not only excellent flexibility (1208.6 % at 25 °C and 1006.3 % at −40 °C) but also impressive ionic conductivity (86.6 mS cm⁻¹ at 25 °C and 73.2 mS cm⁻¹ at −40 °C). The integrated supercapacitor, featuring low interfacial resistance, was successfully fabricated via in situ polymerization of aniline. This supercapacitor exhibits a high areal capacitance of 1158.67 mF cm⁻² at a current density of 0.2 mA cm⁻² and a capacitance retention of >95 % in 2000 charge/discharge cycles, surpassing the performance of most previously reported integrated supercapacitors. This approach enhances the mechanical properties and electrical conductivity of the hydrogel electrolyte, offering a potential application for hydrogel supercapacitors in flexible energy storage devices.