Anion‐Type Solvation Structure Enables Freeze‐Tolerant Aqueous Zinc‐Vanadium Batteries

Abstract

Abstract Aqueous zinc batteries represent a promising solution for large‐scale energy storage, offering inherent safety and cost advantages. However, their subzero operation is fundamentally constrained by severely retarded reaction kinetics of Zn 2+ . Herein, to construct high‐performance, freeze‐tolerant aqueous zinc‐vanadium batteries, 2‐methyltetrahydrofuran (2‐MeTHF) with weak coordination and dissociation capacity is introduced as a functional co‐solvent to reconstruct Zn 2 ⁺ solvation structures from water‐dominated ([Zn(H 2 O) 6 ] 2+ ) to anion‐dominated ([Zn(H 2 O) 2 (OTf − ) 4 ] 2− ) in 1  M Zn(OTf) 2 . The as‐constructed anion‐type solvation configuration creates low‐barrier desolvation/migration ion channels and anion‐rich interface, leading to key improvements in bulk Zn 2 ⁺ ion transport and interfacial stability, benefiting both the anodic and cathodic chemistry. Substantial improvement of Zn plating/stripping reversibility, contributed by promoted Zn‐diffusion kinetics and OTf − ‐derived robust protective interphase, is obtained from 25 to −20 °C, while long‐term structure integrity of NaV 3 O 8 ∙1.5H 2 O cathode, attributed to the prohibition of H 2 O‐driven degradation and dissolution issues, is also effectively maintained. Consequently, even at −20 °C, where the pure aqueous electrolyte hardly works, the Zn||NaV 3 O 8 ∙1.5H 2 O assembled in 2‐MeTHF‐containing electrolyte still presents long‐term cycling durability up to 8000 cycles at 5 A g −1 , with negligible capacity decay throughout the test. This work highlights the significant role of anion‐type solvation of Zn 2+ in achieving wide‐temperature aqueous zinc batteries.