Electrolyte Engineering Enables Stable Zn-Ion Deposition for Long-Cycling Life Aqueous Zn-ion Batteries

Abstract Aqueous zinc metal batteries (AZMBs) directly utilizing Zn metal anode have been regarded as a promising candidate for the next generation commercial batteries featuring high safety, high theoretical capacity, and appealing chemical stability. However, narrow electrochemical stability windows of aqueous electrolytes, uncontrolled dendrite and limited reversibility still plague its practical applications. Herein, we present a strategy via engineering dilute aqueous Zn(OTf)2 solutions electrolytes with a polyethylene glycol (PEG) network, which substantially decreases the activity of water molecules, and simultaneously enables smooth Zn deposition with a (002) textured and a favorable ZnF2-rich SEI. As a result, symmetric cells with PEG-H2O system show record high cyclic performance (9000 h and 8000 h at current densities of 1 and 2 mA cm−2, respectively), superior interfacial stability and dendrite-free morphology after repeated plating/stripping. Additionally, Zn||70%PEG||V2O5 full batteries also deliver a remarkable energy density of 324.3 W h Kg−1 at a power density of 466.9 W Kg−1 and maintain 84.3% of the capacity over 500 cycles at a high current density of 15 A g−1. All these comprehensive results demonstrate that this electrolyte structural engineering can provide a promising direction for designing high reversibility, long-cycling life aqueous Zn metal batteries.