High donor-number and low content electrolyte additive for stabilizing zinc metal anode

Abstract

The aqueous zinc ion batteries (AZIBs) are thought as promising competitors for electrochemical energy storage, though their wide application is curbed by the uncontrollable dendrite growth and gas evolution side reactions. Herein, to stabilize both zinc anodes and water molecules, we developed a modified electrolyte by adding a trace amount of N,N-diethylformanmide (DEF) into the ZnSO4 electrolyte for the first time in zinc ion batteries. The effectiveness of DEF is predicted by the comparison of donor number and its preferential adsorption behavior on the zinc anode is further demonstrated by several spectroscopy characterizations, electrochemical methods, and molecular dynamics simulation. The modified electrolyte with 5% v.t. DEF content can ensure a stable cycling life longer than 3400 h of Zn||Zn symmetric cells and an ultra-reversible Zn stripping/plating process with a high coulombic efficiency of 99.7%. The Zn||VO2 full cell maintains a capacity retention of 83.5% and a 104 mA h g−1 mass capacity after 1000 cycles. This work provides insights into the role of interfacial adsorption behavior and the donor number of additive molecules in designing low-content and effective aqueous electrolytes.