Search

With the emergence of various flexible electronics, the flexible zinc–air battery (ZAB) is considered a promising energy source with low cost, high energy density, and safety. However, gel electrolytes that improve the freezing tolerance and energy efficiency of ZABs are rarely explored. Herein, an organohydrogel electrolyte (OHE) is fabricated by soaking poly(2‐acrylamido‐2‐methylpropanesulfonic acid)/polyacrylamide (PAMPS/PAAm) double‐network hydrogel in aqueous KOH electrolyte with dimethyl sulfoxide (DMSO) additive. The prepared OHE exhibits high mechanical strength and excellent ionic conductivity. In addition, the introduction of DMSO effectively improves freezing tolerance and electrochemical performance especially in energy efficiency of ZABs due to that DMSO can break the hydrogen bonds between water molecules and alter the path of the conventional oxygen evolution reaction in ZAB simultaneously. Compared with the control hydrogel electrolyte, the optimized OHE enables flexible ZABs to not only exhibit an exceptionally low charge voltage of 1.63 V, high energy efficiency of 74.2%, and long cycling life of 177 cycles, but also to operate with an excellent specific capacity of 562 mAh g−1 and energy density of 523.4 Wh kg−1 at −40 °C. Moreover, the obtained flexible ZABs keep a stable output under deformations and extreme low temperature, manifesting a great potential for functional wearable devices. [ABSTRACT FROM AUTHOR]

Hydrogel electrolytes have spurred the development of flexible energy storage devices by endowing them with liquid‐like ion transport and solid‐like mechanical elasticity. However, traditional hydrogel electrolytes always lose these functions in climate change because the internal water undergoes freezing and/or dehydration. In this work, a flexible supercapacitor (OHEC) is assembled based on the organohydrogel electrolyte (OHE) and activated carbon electrode material. The OHE is composed of PAMPS/PAAm double‐network hydrogel soaked from 4 m LiCl/ethylene glycol and exhibits good conductivities (1.9 and 22.9 mS cm−1 at −20 and 25 °C, respectively). The OHEC exhibits broad temperature adaptability (from −20 to 80 °C) and extraordinary resistance to mechanical damage (above 100 kg crushing). The OHEC avoids the polarization at low temperatures and retains 77.8% capacitance retention after storage at −20 °C for 30 days. Without extra sealed packaging, the OHEC maintains remarkable cycling stability (only 8.7% capacitance decay after 10 000 cycles) and retains 77.3% capacitance at 80 °C after 56 h. The outstanding anti‐drying performance and improved interfacial compatibility of OHEC account for the good durability in the high‐temperature environments. Additionally, other salts (such as LiClO4, NaCl, and KCl) with favorable solubility in ethylene glycol can also serve in OHEs for wide temperature range supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carrageenan-based hydrogels with high concentration LiCl (up to 13 M) are synthesized via one-pot method above 90 °C. • CG/PAAm-7Li/K hydrogel shows a high conductivity of 1.9 S/m at − 40 °C. • CG/PAAm-7Li/K based supercapacitor exhibits excellent low-temperature electrochemical properties. Stretchable carrageenan (CG) based double-network (DN) hydrogel has great potential in flexible energy storage devices. To achieve high conductivity at sub-zero temperatures, one-pot synthesis method is adopted for the fabrication of CG/polyacrylamide DN hydrogel with high LiCl concentration (termed CG/PAAm-xLi). In this method, a high temperature above 90 °C is required to fully melt CG network in the presence of high-concentration LiCl and to add the monomers of the second polymer network. Furthermore, by incorporation of small amounts of KCl, the obtained CG/PAAm-7Li/K DN hydrogel shows strong tensile properties with tensile elongation of 567.7%, and fracture energy of 967.3 kJ/m2. In addition, the conductivity of the CG/PAAm-7Li/K DN hydrogel achieves 1.9 S/m at − 40 °C. The flexible supercapacitor prepared by using CG/PAAm-7Li/K hydrogel electrolyte exhibits excellent low-temperature electrochemical properties (specific capacitance of 73.4 F/g, and capacitance retention of 95.6% after 20,000 cycles at − 40 °C). This high-temperature strategy may be extended to construct other ionic polysaccharide-based hydrogel electrolytes with high mechanical property and excellent low-temperature electrochemical performance, showing a broad prospect in the field of flexible electronics. [ABSTRACT FROM AUTHOR]