Ethylene Glycol-Choline Chloride Based Hydrated Deep Eutectic Electrolytes Enabled High-Performance Zinc-Ion Battery.

Aqueous rechargeable zinc-ion batteries (ARZIBs) are considered as an emerging energy storage technology owing to their low cost, inherent safety, and reasonable energy density. However, significant challenges associated with electrodes, and aqueous electrolytes restrict their rapid development. Herein, ethylene glycol-choline chloride (Eg-ChCl) based hydrated deep-eutectic electrolytes (HDEEs) are proposed for RZIBs. Also, a novel VO·nHO@rGO composite is prepared and investigated in combination with HDEEs. The formulated HDEEs, particularly the composition of 1 ml of EG, 0.5 g of ChCl, 4 ml of HO, and 2 M ZnTFS (1-0.5-4-2 HDEE), not only exhibit the lowest viscosity, highest Zn conductivity (20.38 mS cm), and the highest zinc (Zn) transference number (t = 0.937), but also provide a wide electrochemical stability window (>3.2 V vs ZnǁZn) and enabledendrite-free Zn stripping/plating cycling over 1000 hours. The resulting ZnǁVO·nHO@rGO cell with 1-0.5-4-2 HDEE manifests high reversible capacity of ≈365 mAh g at 0.1 A g, high rate-performance (delivered ≈365/223 mAh g at 0.1/10 mA g) and enhanced cycling performance (≈63.10% capacity retention in the 4000 cycle at 10 A g). Furthermore, 1-0.5-4-2 HDEE support feasible Zn-ion storage performance across a wide temperature range (0-80 °C) FInally, a ZnǁVO·nHO@rGO pouch-cell prototype fabricated with 1-0.5-4-2 HDEE demonstrates good flexibility, safety, and durability.