Anion‐Type Solvation Structure Enables Freeze‐Tolerant Aqueous Zinc‐Vanadium Batteries
Jianning Zeng, Zhaoyu Zhang, Xinyi Lan, Guoli Liao, Wencheng Du, Yufei Zhang, Minghui Ye, Zhipeng Wen, Yongchao Tang, Xiaoxu Zhao, Xiaoqing Liu, Chengchao Li
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.