Trace additive-induced molecular interface enables highly reversible zinc anodes for aqueous batteries

Abstract

Zinc (Zn) metal is a highly promising anode material for rechargeable aqueous batteries but suffers from poor reversibility due to dendrite formation and side reactions. Here, we demonstrate that adding trace amounts of N,N-dimethyl-dithiocarbamylpropyl sulfonic acid sodium salt (DPS) into electrolyte can create a self-assembled molecular interfacial layer to boost the reversibility of Zn anodes. Specifically, the hydrophobic −N−CH3 groups and the zincophilic single bondS groups anchor the DP− anions onto Zn anode surface while exposing the hydrophilic −SO3− groups to electrolyte. The resulting self-assembled molecular layer not only effectively restricts lateral Zn2+ ion diffusion but also facilitates homogeneous interfacial Zn2+ ion flux, thereby promoting uniform Zn deposition. Meanwhile, the molecular layer repels H2O molecules and SO42− ions from direct contact with Zn anodes, inhibiting the formation of insulating by-products. As a result, the addition of 0.2 mM DPS enables Zn||Zn symmetric cells to achieve long lifespans of over 3200 h at 2 mA cm−2 and 1 mAh cm−2 and 785 h at 10 mA cm−2 and 10 mAh cm−2. Furthermore, a Zn||MnO2 full cell using the DPS-modified electrolyte can deliver 194.6 mAh g−1 after 600 cycles at 1.0 A g−1, whereas the counterpart cell using pristine ZnSO4 electrolyte short-circuits after 230 cycles. This work provides a facile, cost-effective, and efficient approach to tackling the grand challenges of Zn anodes through the use of trace additives. The proposed strategy is inherently versatile and holds great potential for extension to other rechargeable metal batteries. Graphical abstract: [Figure not available: see fulltext.]