High Coulombic efficiency cathode with nitryl grafted sulfur for Li-S battery

Abstract

The development of lithium sulfur (Li-S) batteries has provided a popular alternative to the current state-of-art battery technologies because of their low cost as well as high theoretical specific energy. However, it is still challenging to develop sulfur cathodes with high Coulombic efficiency due to the polysulfide dissolution problem. Herein, we present a new strategy to improve the Coulombic efficiency by using nitryl grafted sulfur cathode, which is confirmed by in-situ XRD measurement and XPS analysis. The formed SEI layer on the nitryl grafted sulfur cathode could effectively trap the soluble polysulfide and avoid polysulfide migration from cathode into electrolyte, which allows significant improvement in the capacity retention of 80.6% after 450 cycles. In addition, a Coulombic efficiency of ~ 100% is achieved for the nitryl grafted sulfur (Nitryl-S) cathode, which is superior to the value of bare S cathode. The excellent performance is owing to the significantly reduced concentration of soluble polysulfide as evidenced by in-situ UV/Vis spectroscopy analysis. Thus this strategy might open up a new avenue for practical application of Li-S batteries.