Strong Replaces Weak: Design of H-Bond Interactions Enables Cryogenic Aqueous Zn Metal Batteries

Abstract

Despite the numerous advantages of aqueous Zn batteries, their practical application under cryogenic conditions is hindered by the freezing of the electrolyte because the abundance of hydrogen bonds (H-bonds) between H 2 O molecules drives the aqueous system to transform to an orderly frozen structure. Here, a design of H-bond interactions based on the guiding ideology of "strong replaces weak" is proposed. The strong H-bonds formed between introduced eutectic components and water molecules break down the weak Hbonds in the original water molecule network, which contributes to an ultralow freezing point and a high ionic conductivity of 1.7 mS cm −1 at −40 °C. Based on multiperspective theoretical simulations and tailor-made in situ cooling Raman characterizations, it has been demonstrated that substituting weak H-bonds with strong H-bonds facilitates the structural reshaping of Zn 2+ solvation and remodeling of the H-bond network in the electrolyte. Endowed with this advantage, reversible and stable Zn plating/stripping behaviors could be realized at −40 °C, and the full cells display a high discharge capacity (200 mA h g −1 ) at −40 °C with ∼75% capacity retention after 1000 cycles. This study will expand the design philosophy of antifreezing aqueous electrolytes and provide a perspective to promote the adoption of Zn metal batteries for cryogenic environment large-scale energy storage.

Eutectogel with (NH4)2SO4-Based Deep Eutectic Solvent for Ammonium-Ion Supercapacitors

“…The unshifted absorption peak at 613 cm –1 reflected that SO 4 2– anions still paired with cations, but the larger [NH 4 (H 2 O) m (EG) n − m ] + cations would weaken the Coulombic forces between the anions and cations, which endowed DES-5 with a lower freezing point. The result was consistent with the energy difference between the water–water H-bond (−2.41 kcal mol –1 ) and the water–EG H-bond (−3.83 kcal mol –1 ), which led to the disruption of H-bond networks and the depression of the freezing point in an aqueous system …”

Chelating Additive Regulating Zn‐Ion Solvation Chemistry for Highly Efficient Aqueous Zinc‐Metal Battery

“…This indicated that the stability of water molecule clusters increased and the proportion of free water decreased. [17,19] These results suggested that the addition of N-ac contributed to the reduction of water molecules within the Zn-ions solvation sheaths as well as the free water in the electrolyte, thus inhibiting the various water-related side-reactions, HER and Zn-metal corrosion. In addition, Fourier…”