Tough and Antifreezing Organohydrogel Electrolyte for Flexible Supercapacitors with Wide Temperature Stability

Abstract

Hydrogels bridged by some alcohol compounds are reported to be useful for high tough and antifreezing properties of electronics and energy storage devices. However, the relationship between the structures of the alcohols on the mechanical and antifreezing properties is not clear yet. For a better understanding of the relationship and influence mechanism, conjoined-network organohydrogels connected with three typical alcohols (ethylene glycol, glycerol, and sorbitol) as bridging molecules were constructed by utilizing a poly(vinyl alcohol)/alginate-calcium (PVA/Alg-Ca) double-network hydrogel as a substrate. The results displayed that the organohydrogels exhibit high mechanical properties with a maximum at 2.4 MPa and good antifreezing performance with the lowest value at −61 °C. By further analyzing the mechanism by Fourier transform infrared spectroscopy (FTIR) and derivative thermogravimetry (DTG), it was observed that the hydrogen bonds among the bridging molecules, polymer chains, and water were considered to play a decisive role in the high performance of the organohydrogels. A high number of hydroxyl groups in the bridging molecules could be conducive to the better entanglement of polymer chains but less interaction with water. Nevertheless, under the synergistic effect of the hydrogen bonds and high-concentration free ions, the organohydrogels also delivered high ionic conductivity. Furthermore, an all-in-one flexible supercapacitor based on the organohydrogels was assembled. It delivered a superior areal specific capacitance of 140.75 mF cm–2 at 1.0 mA cm–2 and exhibited good flexibility and electrochemical stability under different bending conditions and a wide working temperature range (−20 to 60 °C). It could be promisingly applied in flexible energy storage devices working even in subzero environments.