Reversible electrochemical oxidation of sulfur in ionic liquid for high-voltage Al−S batteries

. The sulfur oxidation is: 1) highly reversible with an efficiency of ~94%; and 2) workable within a wide range of high potentials. As a result, the Al-S battery based on sulfur oxidation can be cycled steadily around ~1.8 V, which is the highest operation voltage in Al-S batteries. The study of sulfur oxidation process benefits the understanding of sulfur chemistry and provides a valuable inspiration for the design of other high-voltage metal-sulfur batteries, not limited to Al-S configurations.