Impregnated Sulfur in Carbonized Nitrogen-containing Porous Organic Frameworks as Cathode with High Rate Performance and Long Cycle Life for Lithium-sulfur Batteries

The undesirable cycling performance caused by soluble polysulfides shuttling between anode and cathode has been considered as the main challenge that has hindered its practical applications for lithium-sulfur(Li-S) batteries. To solve this issue effectively, a nitrogen-containing porous carbon, namely JUC-Z2-900, developed from a porous organic framework, namely JUC-Z2, bearing a high surface area(805 m(2)/g), small pore size(0.5 nm) and nitrogen doping(2.15%, mass fraction), has been used as a host material for Li-S batteries. The micropores of JUC-Z2-900 can confine the smaller sulfur molecules S2-4, which can essentially alleviate the critical problem of polysulfide dissolution. Furthermore, nitrogen-containing JUC-Z2-900 can promote chemical adsorption of sulfur. The above two factors can improve the electrochemical performance of Li-S batteries effectively. To compare the effects of sulfur contents and melt-diffusion strategy in JUC-Z2-900/S composites, a series of JUC-Z2-900/S composites was synthesized and their electrochemical performances were explored, indicating good rate performance and excellent cycling stability of the composites contributed by both appropriate mass percentage of sulfur and its confinement in the micropores.