Weakly solvating aqueous-based electrolyte facilitated by a soft co-solvent for extreme temperature operations of zinc-ion batteries†
Abstract
The aqueous zinc-ion battery (AZIB) is a promising option for grid-scale energy storage, but it faces challenges from parasitic water-related reactions and limited operational temperature range. Replacing H2O molecules in the solvation sheath of Zn2+ with strongly solvating co-solvents can effectively suppress water-related side reactions. However, the excessive Zn2+–co-solvent interaction can cause a large activation energy of desolvation (Ea) and the decomposition of the co-solvent may introduce non-ionic conductive solid electrolyte interphase (SEI) species. Hence, we propose a weakly solvating electrolyte that adopts diethylene glycol dimethyl ether (G2) as a soft co-solvent. The G2 has a moderate Gutmann donor number (19 kcal mol−1) and a low dielectric constant (7.4), which reduces the presence of water in the solvation sheath and enhances Zn2+–anion interaction. This electrolyte achieves an optimal Ea and a robust anion-derived SEI (ZnS–ZnSO3–ZnF2) on the zinc anode, allowing highly reversible Zn plating/stripping for over 7500 hours. The strong G2–H2O interaction enables G2 to bind free H2O and reconstruct the hydrogen bond network, which prevents water decomposition and widens the electrolyte's operational temperature range (−60 °C to 60 °C). The Zn//KV12O30−y·nH2O (KVOH) full battery delivers a high-capacity retention of 91.2% following 8000 cycles at 5.0 A g−1 at room temperature. It also achieves capacity retention of 82.9% over 4000 cycles (0.1 A g−1) at −45 °C and 86.5% for 1200 cycles (5.0 A g−1) at 60 °C, respectively. This work optimizes interface chemistry and temperature adaptability of AZIBs, offering guidance for designing weakly solvating aqueous-based electrolytes towards practical application.
- This article is part of the themed collection: Materials for energy storage and conversion: Chemical Science symposium collection