Metal-organic-framework derived NiS2/C hollow structures for enhanced polysulfide redox kinetics in lithium-sulfur batteries.

ABSTRACT

To cope with the shuttling of soluble lithium polysulfides in lithium-sulfur batteries, confinement tactics, such as trapping of sulfur within porous carbon structures, have been extensively studied. Although performance has improved a bit, the slow polysulfide conversion inducing fast capacity decay remains a big challenge. Herein, a NiS2/carbon (NiS2/C) composite with NiS2 nanoparticles embedded in a thin layer of carbon over the surface of micro-sized hollow structures has been prepared from Ni-metal-organic frameworks. These unique structures can physically entrap sulfur species and also influence their redox conversion kinetics. By improving the reaction kinetics of polysulfides, the NiS2/carbon@sulfur (NiS2/C@S) composite cathode with a suppressed shuttle effect shows a high columbic efficiency and decent rate performance. An initial capacity of 900 mAh g-1 at the rate of 1 C (1 C = 1675 mA g-1) and a low-capacity decline rate of 0.132% per cycle after 500 cycles are obtained, suggesting that this work provides a rational design of a sulfur cathode.