Ultra‐stable Zinc Metal Anodes at −20 °C through Eutectic Solvation Sheath in Chlorine‐functionalized Eutectic Electrolytes with 1,3‐Dioxolane

Abstract The brain‐storm of designing low‐cost and commercialized eutectic electrolytes for zinc (Zn)‐based electrochemical energy storage (ZEES) remains unresolved and attractive, especially when implementing it at low temperatures. Here, we report an appealing layout of advancing chlorine‐functionalized eutectic (Cl‐FE) electrolytes via exploiting Cl anion‐induced eutectic interaction with Zn acetate solutions. This novel eutectic liquid shows high affinity to collaborate with 1,3‐dioxolane (DOL) and is prone to constitute Cl‐FE/DOL‐based electrolytes with a unique inner/outer eutectic solvation sheath for the better regulation of Zn‐solvating neighboring and reconstruction of H‐bonding. The side reactions are effectively restricted on Zn anodes and a high Coulombic efficiency of 99.5 % can be achieved over 1000 cycles at −20 °C with Zn//Cu setups. By prototyping scale‐up Zn‐ion pouch cells using the optimal eutectic liquid of 3ZnOAc 1.2 Cl 1.8 ‐DOL, we obtain improved electrochemical properties at −20 °C with a high capacitance of 203.9 F g −1 at 0.02 A g −1 in a range of 0.20–1.90 V and long‐term cycling ability with 95.3 % capacitance retention at 0.2 A g −1 over 3,000 cycles. Overall, the proposal of ideal Cl‐FE/DOL‐based electrolytes guides the design of sub‐zero and endurable aqueous ZEES devices and beyond.