Electrochemical Properties of Lithium–Sulfur Cells in a Very Wide Range of Sulfur Concentration

摘要

This paper examines the influence of the sulfur concentration on the electrochemical properties of Lia??S cells over a very wide sulfur concentration range of 1.5 to 14.2 m. The sulfur utilization decreased gradually from 74 to 40% with increasing sulfur concentration in this concentration range. Surprisingly, the Lia??S cells successfully operated with a considerable capacity (675 mAh/g) even under an extremely high sulfur concentration of 14.2 m. At a high rate of 5.0 C, the cells with 9.8 and 11.5 m sulfur showed much poorer rate capabilities than those with 2.3 and 5.6 m sulfur. This feature was attributed mainly to the significant ohmic drop and large reaction overpotential due to chemical reactions coupled with the electrode reactions of sulfur and polysulfides. In addition, there was a notable variation in the cycle performance with a change in the sulfur concentration. Interestingly, higher capacity retention was observed in 5.6 and 9.8 m sulfur than in low (2.3 m) and high (11.5 m) sulfur concentrations.