Low Current-Density Stable Zinc-Metal Batteries Via Aqueous/Organic Hybrid Electrolyte

Zinc-metal batteries (ZMBs) are promising for large-scale energy storage devices due to their intrinsically safe, low-cost and environmentally friendly nature. ZMBs with vanadium-based cathodes have exhibited excellent performance, however, many side reactions due to the presence of innumerable water molecules in aqueous electrolyte hinder their commercialization. Herein, high-proportioned polyethylene glycol was introduced as solvent to form an aqueous/organic hybrid electrolyte, which limits the activity of free water molecules and lowers the risk of side reactions, such as cathode dissolution, zinc dendrites and H-2 evolution. As a result, a good reversible zinc plating/stripping over 3000 h for zinc anode and an excellent cycle stability with 96 % retention after 50 cycles at low current density of 0.1 A g(-1) for vanadium-based cathode were obtained, respectively. Importantly, to simulate the stability in actual application environment, a test mode at low current density under both continuous and intermittent electrochemical charge/discharge was conducted, which further demonstrated the superiority of this hybrid electrolyte. Finally, as a practical illustration, the pouch cells of 3 cmx3 cm exhibit a high capacity of 300 mAh g(-1) at 0.1 A g(-1) with a good retention of 81.7 % after 200 cycles, and even up to 500 cycles at 0.5 A g(-1). This work is expected to provide new opportunities for high-performance hybrid electrolyte for the practical ZMBs.

Automated summary

In this study, high-proportioned polyethylene glycol was introduced as solvent in the electrolyte of zinc-metal batteries, effectively limiting the activity of free water molecules and reducing the occurrence of side reactions. The introduction of this hybrid electrolyte led to improved reversible zinc plating/stripping and cycle stability. The experimental results also demonstrated the superiority of this hybrid electrolyte in both continuous and intermittent electrochemical charge/discharge modes.