Understanding the Oxidation and Reduction Reactions of Sulfur in Rechargeable Aluminum-Sulfur Batteries with Deep Eutectic Solvent and Ionic Liquid Electrolytes

Al-based batteries are promising next-generation rechargeable batteries owing to the abundance of raw materials and their high potential energy density. The Al−S system has attracted considerable attention because of its high energy density and low cost. However, its low discharge voltage plateau (0.6–1.2 V) hampers its practical application. Herein, eight ionic liquids or deep eutectic solvents were studied as electrolyte candidates for an Al−S cell. This was the first study to demonstrate that an Al−S cell based on an AlCl3/acetamide electrolyte (1.3 molar ratio) showed high discharge voltage plateaus (1.65–1.95 V) and a charging cut-off voltage of 2.5 V in Al−S cells. An Al−S cell of 0.33 mAh capacity with the AlCl3/acetamide electrolyte successfully lit up a red LED (forward voltage 1.6–2.0 V) for around 2 h. This work may help in promoting the development of high-performance and low-cost Al−S cells.