Unleashing Ultrahigh Capacity and Lasting Stability: Aqueous Zinc-Sulfur Batteries

Abstract

Despite of multifarious dominance of sulfur-based batteries, polysulfide-shuttling and use of high-cost organic electrolytes with flammability risks hinder their applicability as commercial devices. Herein a polysulfide-free aqueous zinc-sulfur (Zn─S) rechargeable battery is explored, which offers a low-cost and environmentally friendly energy storage system being Zn and Sulfur (S) highly abundant with high theoretical capacity. However, the stability of Zn anode is quite challenging due to dendritic growth and corrosion leading to the capacity decay. This work showcases the utilization of ethylene glycol (EG) and iodine (I₂) as an electrolyte additive in aqueous zinc acetate [Zn(OAc)₂] electrolyte for stabilizing the Zn─S battery performance. EG as an additive is able to mitigate the corrosion rate of the Zn electrode by 15 times which is supported by molecular dynamics simulation. The assembled Zn─S battery delivered an outstanding capacity of 1210 mA h g⁻¹ at 0.1 C with a 91% capacity retention even after 250 cycles, along with remarkable reversible prolonged cycling stability of 3000 cycles at 1 C, with 64.5% capacity retention. More importantly, in situ electrochemical Raman spectroscopy is utilized to monitor the real-time formation of zinc sulfide (ZnS) as a single discharge product and simultaneously debunking the polysulfide shuttling in the system which is further supported by XPS, UV-Vis and IR spectroscopy.