Enormous-sulfur-content cathode and excellent electrochemical performance of Li-S battery accouched by surface engineering of Ni-doped WS2@rGO nanohybrid as a modified separator.

ABSTRACT

The poor conductivity of sulfur, the lithium polysulfide's shuttle effect, and the lithium dendrite problem still impede the practical application of lithium-sulfur (Li-S) batteries. In this work, the ultrathin nickel-doped tungsten sulfide anchored on reduced graphene oxide (Ni-WS2@rGO) is developed as a new modified separator in the Li-S battery. The surface engineering of Ni-WS2@rGO could enhance the cell conductivity and afford abundant chemical anchoring sites for lithium polysulfides (LiPSs) adsorption, which is convinced by the high adsorption energy and the elongate SS bond given using density-functional theory (DFT) calculation. Concurrently, the Ni-WS2@rGO as a modified separator could effectively catalyze the conversion of LiPSs during the charging/discharging process. The Li-S cell with Ni-WS2@rGO modified separator achieves a high initial capacity of 1160.8 mA h g-1 at the current density of 0.2C with a high-sulfur-content cathode up to 80 wt%, and a retained capacity of 450.7 mA h g-1 over 500 cycles at 1C, showing an efficient preventing polysulfides shuttle to the anode while having no influence on Li+ ion transference across the decorating separator. The strategy adopted in this work would afford an effective pathway to construct an advanced functional separator for practical high-energy-density Li-S batteries.