Abstract:

Lithium sulfur (Li-S) battery with the high theoretical energy density has been considered as the most promising next generation of rechargeable batteries, being the research hot topic in the last 10 years. However, the cycle and rate performances could not satisfy the actual requirements. Here, di-2,2,2-trifluoroethyl carbonate (DTFEC) has been investigated as electrolyte addictive to improve the electrochemical performances of the Li-S batteries for the first time. The electrochemical test results show that the additive has a great influence on the performance of the battery and which is related to the amount of addition. With 5% DTFEC (volume ratio) added, the sulfur composite (S@pPAN) cathodes exhibit the best cycle stability and rate performance at room temperature. The capacity retention is improved about 20% compared with conventional electrolyte after 200 cycles at 1C and the reversible capacity is maintained at about 1246.3 mA·h·g-1 even at 7 C. This study indicates that DTFEC is a favorable additive in conventional liquid electrolytes for rechargeable lithium sulfur batteries.

Key words: lithium sulfur (Li-S) batteries, DTFEC, addictive, electrochemical performances