Stable and High-Energy Zinc-Iodine Battery through Deep Eutectic Solvents (DES)

Abstract

The growing global need for sustainable energy has pushed the search for cost-effective and safe battery technologies. The aqueous zinc-iodine battery is known for its cost-effectiveness and high energy storage. However, several problems make it difficult to commercialize zinc-iodine batteries. The activity of H2O (active water) triggering the hydrogen evolution reaction (HER) causes side reactions on the Zn surface. Additionally, when the polyiodide which produced at the cathode during charging shuttles to the Zn surface, it not only induces self-discharge but also causes adverse reactions on the Zn surface. These side-reactions also promote dendrite growth on the Zn anode and contribute to battery decay. To address these problems, we introduce an innovative Zn chloride-sulfolane (SL)-water-KI quaternary deep eutectic solvent (DES) (ZSW) system. FT-IR and Raman spectroscopy analyses demonstrate that when ZSW is composed, the strong interaction among its constituents significantly reduces the amount of active water within the electrolyte. Noteworthy is the ZSW system's ability to exhibit a higher proportion of suppressed water compared to active water, even with the addition of water. Additionally, ZSW does not produce polyiodide during charging, unlike conventional aqueous electrolytes. The study presents compelling evidence of the ZSW system's superior dendrite suppression and energy retention properties compared to conventional aqueous systems. Specific performance metrics reveal remarkable stability and energy efficiency, with a specific capacity of 247 mAh/g at 1 A/g and 176 mAh/g at 5 A/g. These findings represent a significant advancement in Zn-based battery technologies, paving the way for potential commercialization and widespread adoption in the energy storage sector.