Promoting the conversion of Li2S by functional additives phenyl diselenide in Lithium–Sulfur batteries

Lithium–Sulfur (Li–S) battery is a promising device in the field of electrochemical energy storage since its high specific capacity and low cost. However, the low insoluble Li2S conversion efficiency and uncontrollable deposition on the electrodes lead to low sulfur utilization, poor reversibility and rapid capacity decay. Consequently, the practical application of Li–S battery is limited. Herein, phenyl diselenide (PDSe) is added into the conventional electrolyte try to improve the batteries performance. The results show that the Se–Se bond in PDSe is broken and the Li–S bond in Li2S is elongated induced by PDSe. Moreover, PDSe promotes Li2S conversion and reduces Li2S deposition on the electrodes. As a result, the batteries using the electrolyte with PDSe exhibit enhanced discharge capacity and improved rate performance. Particularly, the batteries with 5.0 wt% PDSe additive exhibit a high initial discharge capacity of 1585.6 mAh g−1, even after 300 cycles at 0.5 C, the batteries still maintain 916.5 mAh g−1, which is much higher than conventional batteries of 618.7 mA h g−1.