Interface enhanced well-dispersed Co9S8 nanocrystals as an efficient polysulfide host in lithium–sulfur batteries

Abstract

The high specific capacity and energy density of lithium–sulfur batteries have attracted strong considerations on their fundamental mechanism and energy applications. However, polysulfide shuttle is still the key issue that impedes the development of Li–S batteries. Exploring nanocrystal hosts for polysulfide immobilization and conversion is a promising way. In this contribution, we have investigated well-dispersed Co9S8 nanocrystals grown on graphene oxide (GO) nanosheets with different degrees of dispersion as cathode host materials for Li–S batteries. The Co9S8-GO composite with 1 wt% GO (GCS1) has an average crystal size of 76 nm and shows the strongest adsorption capability toward lithium polysulfides. When used as the host material for the cathode of Li–S batteries, the GCS1-sulfur composite exhibits an initial specific capacity of ~1000 mAh g−1 at 0.5 C and shows an average decay rate of 0.11% for 500 cycles. This work on the dispersion control of Co9S8 nanocrystals may inspire more investigations on well-dispersed nanocrystal based hosts for Li–S batteries.