Antifreezing Zwitterionic Hydrogel Electrolyte with High Conductivity of 12.6 mS cm⁻¹ at −40 °C through Hydrated Lithium Ion Hopping Migration

Abstract

Hydrogel electrolytes have high room-temperature conductivity and can be widely used in energy storage device. However, hydrogels suffer from the inevitable freezing of water at subzero temperatures, resulting in the diminishment of their conductivity and mechanical properties. How to achieve high conductivity without sacrificing hydrogels' flexibility at subzero temperature is an important challenge. To address this challenge, a new type of zwitterionic polymer hydrogel (polySH) electrolytes is fabricated. The anionic and cationic counterions on the polymer chains facilitate the dissociation of LiCl. The antifreezing electrolyte can be stretched to a strain of 325% and compressed to 75% at −40 °C and possesses an outstanding conductivity of 12.6 mS cm −1 at −40 °C. A direct hopping migration mechanism of hydrated lithium-ion through the channel of zwitterion groups is proposed. The polySH electrolyte-based-supercapacitor (SC) exhibits a high specific capacitance of 178 mF cm −2 at 60 °C and 134 mF cm −2 at −30 °C with a retention of 81% and 71% of the initial capacitance after 10 000 cycles, respectively. The overall merits of the electrolyte will open up a new avenue for advanced ionic conductors and energy storage device in practical applications.

Environmentally Compatible Wearable Electronics Based on Ionically Conductive Organohydrogels for Health Monitoring with Thermal Compatibility, Anti‐Dehydration, and Underwater Adhesion

“…The phenomenon can be explained by the environmental adaption of organohydrogel, in which multiple hydrogen bonds between CPA and water molecules improve water retain capability and freezing tolerance. [ 37 ] Furthermore, the results of resistances at these temperatures indicate that L‐PAA‐H cannot bear a wide range of temperatures, displaying deteriorated ionic conductivity, while the resistance of L‐PAA‐OH remains relatively stable at different temperatures (Figure 2h). Notably, at high temperature, L‐PAA‐OH presents a slight increase in resistance, which may be caused by inferior contact between the organohydrogel and electrodes due to the increased stiffness at elevated temperature.…”

Flexible Quasi‐Solid‐State High‐Performance Aqueous Zinc Ion Hybrid Supercapacitor with Water‐in‐Salt Hydrogel Electrolyte and N/P‐Dual Doped Graphene Hydrogel Electrodes

“…H is the melting enthalpy of pure water, ∆ m 0 H = 333.5 J g −1 . [30] The freezing point of water in 1 m Zn(CH 3 COO) 2 was at −23 °C and was pushed to below −70 °C in the concentrated mixed electrolyte. This will allow the electrolyte to have a wider temperature operating range, which was an advantage that dilutes aqueous solutions cannot acquire without the addition of organic solvents.…”

A highly sensitive and ultra-stretchable zwitterionic liquid hydrogel-based sensor as anti-freezing ionic skin

“…The strain sensing mechanism was attributed to the resistance change in different strains when the hydrogel was stretched. 40,41 In the original state, the relatively loose network will enhance the conductivity since it enables more exibility and a broader pathway for charge transfer. Under stretching, the hydrogel deforms and the conductive path becomes narrow due to the presence of the zwitterionic networks, resulting in a decrease in the transmission capacity, which causes a temporary increase of relative resistance at the stretching stage.…”