High efficiency immobilization of sulfur on nitrogen-enriched mesoporous carbons for Li-S batteries.

Nitrogen-enriched mesoporous carbons with tunable nitrogen content and similar mesoporous structures have been prepared by a facile colloid silica nanocasting to house sulfur for lithium-sulfur batteries. The results give unequivocal proof that nitrogen doping could assist mesoporous carbon to suppress the shuttling phenomenon, possibly via an enhanced surface interaction between the basic nitrogen functionalities and polysulfide species. However, nitrogen doping only within an appropriate level can improve the electronic conductivity of the carbon matrix. Thus, the dependence of total electrochemical performance on the nitrogen content is nonmonotone. At an optimal nitrogen content of 8.1 wt %, the carbon/sulfur composites deliver a highest reversible discharge capacity of 758 mA h g(-1) at a 0.2 C rate and 620 mA h g(-1) at a 1 C rate after 100 cycles. Furthermore, with the assistance of PPy/PEG hybrid coating, the composites could further increase the reversible capacity to 891 mA h g(-1) after 100 cycles. These encouraging results suggest nitrogen doping and surface coating of the carbon hosts are good strategies to improve the performance carbon/sulfur-based cathodes for lithium-sulfur batteries.