N-doped carbyne polysulfide as cathode material for lithium/sulfur batteries

A nitrogen-doped carbyne polysulfide (N-CAS) has been prepared by heating the mixture of nitrogen-doped carbyne analogue (N-CA) and sulfur. The nitrogen-doped carbyne analogue was synthesized by the dehydrochlorination and polymerization of 1, 1, 2-trichloroethane and urea. The XPS characterization indicated that nitrogen atoms have been effectively doped into the carbon skeleton with a nitrogen content of 4.32 wt%, and the obtained N-CAS cathode has a porous structure with uneven pore width. The electrochemical results showed that the N-CAS cathode can deliver a high initial capacity (1570mAh/g at a current density of 200 mA/g) and rate capability (500mAh/g at 2000 mA/g), and after 300 cycles, it displays a reversible capacity as high as 900mAh/g in carbonic ester electrolyte, which are better than that of non-doped carbyne polysulfide. These results suggest that doped nitrogen have electrostatic interaction on the lithium polysulfides to improve electrochemical stability and accelerate redox dynamics.