Tough Hydrogel Electrolytes for Anti‐Freezing Zinc‐Ion Batteries

Abstract

As the soaring demand for energy storage continues to grow, batteries that can cope with extreme conditions are highly desired. Yet, existing battery materials are limited by weak mechanical properties and freeze‐vulnerability, prohibiting safe energy storage in devices that are exposed to low temperature and unusual mechanical impacts. Herein, a fabrication method harnessing the synergistic effect of co‐nonsolvency and “salting‐out” that can produce poly(vinyl alcohol) hydrogel electrolytes with unique open‐cell porous structures, composed of strongly aggregated polymer chains, and containing disrupted hydrogen bonds among free water molecules, is introduced. The hydrogel electrolyte simultaneously combines high strength (tensile strength 15.6 MPa), freeze‐tolerance (< −77 °C), high mass transport (10× lower overpotential), and dendrite and parasitic reactions suppression for stable performance (30 000 cycles). The high generality of this method is further demonstrated with poly(N‐isopropylacrylamide) and poly(N‐tertbutylacrylamide‐co‐acrylamide) hydrogels. This work takes a further step toward flexible battery development for harsh environments.

Simultaneous Inhibition of Zn Dendrites and Polyiodide Ions Shuttle Effect by an Anion Concentrated Electrolyte Membrane for Long Lifespan Aqueous Zinc–Iodine Batteries

“…The measured mechanical property of the ACE-10 membrane is superior than many recently reported hydrogel electrolytes and separators, but which still can not reach the high level of tensile strength for the nanocellulose-carboxymethylcellulose electrolyte. − These results suggest that the ACE-10 membrane has a good application prospect as an electrolyte for Zn–I 2 batteries.…”

Salting-Out Effect Realizing High-Strength and Dendrite-Inhibiting Cellulose Hydrogel Electrolyte for Durable Aqueous Zinc-Ion Batteries

“…Finally, the obtained CMC film was soaked in concentrated aqueous solution of 7 M KAc + 1 M ZnAc 2 for 2 days to form Con-CMC hydrogel electrolyte. The selection of KAc is due to its high solubility in water and strong ability to improve freezing tolerance . Furthermore, both K + cation and Ac – anion are good kosmotropic ions, which can easily bring about the salting-out effect when the concentrations of these two ions are high .…”

“…The selection of KAc is due to its high solubility in water and strong ability to improve freezing tolerance . Furthermore, both K + cation and Ac – anion are good kosmotropic ions, which can easily bring about the salting-out effect when the concentrations of these two ions are high . Such effect originates from the strengthened polymer–polymer interactions and weakened water–polymer interactions, resulting in the aggregation of CMC chains with more hydrogen bonding and cross-linking sites and the increased degree of crystallinity. , Thanks to that, the mechanical properties of the Con-CMC hydrogel electrolyte can be significantly improved, compared to the Dil-CMC hydrogel electrolyte that was obtained by soaking the CMC hydrogel in a relatively dilute aqueous solution of 1 M ZnAc 2 .…”

Recent progress in structural modification of polymer gel electrolytes for use in solid-state zinc-ion batteries

“…Yan et al mixed potassium acetate (KAc) with PVA and zinc acetate (ZnAc) using the “salting out” and freezing resistance of K + . 138 The designation 416 solution is the mass ratio of KAc/ZnAc salt concentration which can maintain 1 mA cm −2 current density with 150 mV overpotential at −20 °C (Fig. 10e) and retain 0.6 mA cm −2 current density at −30 °C.…”