Abstract:

The poor mechanical properties of hydrogel electrolytes and the freezing of water at low temperatures affect their ionic conductivity, thereby hindering their application in energy storage devices and electronic conductors. In this study, a type of antifreezing organic hydrogel with high mechanical properties and conductivity is fabricated. The electrolyte was synthesized via free-radical polymerization by adding soy protein isolates and using acrylamide and methacrylic ethyl sulfobetaine as monomers in a mixed solution of dimethyl sulfoxide/H₂O in the presence of lithium chloride. The fabricated hydrogel electrolyte exhibits good ionic conductivity (maximum 37.5 mS/cm), good mechanical properties (maximum stress 69 kPa and maximum strain 762.5%), and high toughness and fatigue resistance. Furthermore, the fabricated electrolyte shows a good response under varying strain and temperature conditions with a wide sensing window and good stability. Additionally, supercapacitors based on this electrolyte show good electrochemical performance between 20 ℃ and -20 ℃. In other words, at 20 ℃, the capacitances of the supercapacitor are 62.1 and 30 F/g at current densities of 0.2 and 5 A/g respectively, while at -20 ℃, the capacitance can maintain 59% of the value obtained at 20 ℃. Moreover, the supercapacitor can maintain 92% of the capacitance after 10 000 cycles, showing good cyclic stability.

Key words: high conductivity, antifreezing, organic hydrogel, supercapacitor, sensor