文摘
The mechanism of the sulfur cathode in Li–S batteries has been proposed. It was revealed by the real-time quantitative determination of polysulfide species and elemental sulfur by means of high-performance liquid chromatography in the course of the discharge and recharge of a Li–S battery. A three-step reduction mechanism including two chemical equilibrium reactions was proposed for the sulfur cathode discharge. The typical two-plateau discharge curve for the sulfur cathode can be explained. A two-step oxidation mechanism for Li<sub>2sub>S and Li<sub>2sub>S<sub>2sub> with a single chemical equilibrium among soluble polysulfide ions was proposed. The chemical equilibrium among S<sub>5sub><sup>2–sup>, S<sub>6sub><sup>2–sup>, S<sub>7sub><sup>2–sup>, and S<sub>8sub><sup>2–sup> throughout the entire oxidation process resulted for a single flat recharge curve in Li–S batteries.