Boosted Capacity and Stability of Aqueous Iron-Sulfur Battery using DMSO as an Electrolyte Additive

Exploring metal-sulfur batteries with low cost, high safety, and capacity is the need of the hour for large storage applications. Iron (Fe) being a highly abundant and cost-effective element, provides an excellent option as an anode material which on coupling with abundant sulfur (S) in an aqueous electrolyte will be a game-changing approach. Despite a promising outlook, the stability of Fe anode due to side reactions in aqueous electrolytes and inherent corrosion tendencies limit their performance. Herein, we have explored dimethyl sulfoxide (DMSO) as an electrolyte additive in iron percholorate (Fe(ClO₄)₂ for aqueous Fe-S battery, which exhibited high specific capacity of 1145 mAh g^-1 at 50 mA g^-1 with remarkable cycling stability for 400 continuous cycles at 2.0 and 0.5 A g^-1 current densities with 72% and 98% capacity retention respectively without replacing the Fe-anode. The addition of DMSO, suppressed parasitic hydrogen evolution reaction (HER) by 6.7 times and mitigated the corrosion rate of iron electrodes by 2.2 times as evidenced by the spectroscopic and gas chromatography techniques. The molecular dynamics (MD) simulations revealed that DMSO engages the water molecules through hydrogen bonding which reduced the fraction of free water molecules available for HER and corrosion of iron electrodes.