Antifreezing Proton Zwitterionic Hydrogel Electrolyte via Ionic Hopping and Grotthuss Transport Mechanism toward Solid Supercapacitor Working at −50 °C

Abstract

Hydrogel electrolyte is widely used in solid energy storage devices because of its high ionic conductivity, environmental friendliness, and non-leakage property. However, hydrogel electrolyte is not resistant to freezing. Here, a high proton conductive zwitterionic hydrogel electrolyte with super conductivity of 1.51 mS cm -1 at −50 °C is fabricated by random copolymerization of acrylamide and zwitterionic monomer in the presence of 1 m H 2 SO 4 and ethylene glycol (EG). The antifreezing performance and low temperature conductivity are ascribed to hydrogen bonds and ionic bonds between the components and water molecules in the system and can be tuned by changing the monomer ratio and EG contents. The proton hopping migration on the ionic group of the polymer chains and Grotthuss proton transport mechanism are responsible for the high proton conductivity while Grotthuss transport is dominated at the glassy state of the polymer chains. The electrolyte-assembled supercapacitor (SC) offers high specific capacitance of 93.5 F g -1 at 25 °C and 62.0 F g -1 at −50 °C with a capacitance retention of 91.1% and 81.5% after 10 000 cycles, respectively. The SC can even work at −70 °C. The electrolyte outperforms most reported antifreezing hydrogel electrolytes and has high potential in low-temperature devices.

Multifunctional Organohydrogel with Ultralow‐Hysteresis, Ultrafast‐Response, and Whole‐Strain‐Range Linearity for Self‐Powered Sensors

“…It was because that the addition of Eg in the solvent destroyed the original hydrogen bonding network caused by the competition with hydrogen and oxygen in the water molecules, which kept the effective work of Grotthuss mechanism to maintain the conductivity. [50][51] It further affected the conductive properties of the organohydrogels as a result. Moreover, we also performed a differential scanning calorimetry (DSC) test to determine the crystallization temperature of different hydrogels and the results are displayed in Figure 4d.…”

Design Strategies and Recent Advancements for Low‐Temperature Aqueous Rechargeable Energy Storage

“…Reproduced with permission. [ 124 ] Copyright 2022, Wiley‐VCH. c) The schematic of intermolecular interactions in the ZnCl 2 ‐TC‐based sAHE.…”

“…The well balance between antifreezing characteristic (Figure 11a) and low-temperature performance (Figure 11b) can be simultaneously achieved by simply adjusting the EG content in the H 2 SO 4 -acrylamide-zwitterionic[(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl)ammonium hydroxide (H 2 SO 4 -AM-SBMA) system. [124] To further reduce the direct contact among water molecules, AN and glycerol were simultaneously added to the PAM based HE. [125] DFT results revealed that both the formation energy of glycerol-H 2 O and PAM-H 2 O were lower than that of H 2 O-H 2 O, indicating that almost no free water existed in the glycerol-AN-PAM-H 2 O system.…”

“…Figure 11. a) DSC results of H 2 SO 4 -AM-SBMA with different EG content. b) The optical image of 4 SCs connected in serial lighting up LED bulbs.Reproduced with permission [124]. Copyright 2022, Wiley-VCH.…”

Ultrahigh conductivity and antifreezing zwitterionic sulfobetaine hydrogel electrolyte for low-temperature resistance flexible supercapacitors

“…One such salt is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), which has both positive and negative groups in the molecular structure that can inhibit ice nucleation in water at subzero temperature due to the strong interaction between the zwitterionic groups and water, 28,31 and thus this is considered an important option to use in low-temperature hydrogel electrolytes. SBMA can easily copolymerize with 2-hydroxyethyl acrylate, 32 acrylamide, 29 and acrylic acid 33 in the presence of 7 M LiCl, EG/H 2 SO 4 and 7.5 M ZnCl 2 , respectively, to form hydrogel electrolytes, which have exhibited ionic conductivities of 1.26 S m −1 (−40 °C), 0.151 S m −1 (−50 °C), and 1.56 S m −1 (−60 °C), respectively. The most important such electrolyte, SBMA–PAM electrolyte, can work in a wide temperature window (−40 to 80 °C) through the dissolution–crystallization transition of CH 3 COONa in hydrogels.…”