Reducing polarization of lithium-sulfur batteries via ZnS/reduced graphene oxide accelerated lithium polysulfide conversion

Abstract

Polarization of lithium-sulfur (Li-S) batteries consumes energy density upon cycling, which precludes their practical application in state-of-the-art devices. Herein a conformal zinc sulfide/reduced graphene oxide/elemental sulfur (ZnS/rGO/S) composite is synthesized and used as cathode materials in Li-S batteries. The synergetic regulation of ohmic, concentration, and electrochemical polarization decreases the overpotential and improves the cycling performance of the Li||ZnS/rGO/S cell. Combining theoretical calculations and experimental results, it is revealed that the ZnS spheres can absorb lithium polysulfide (LPS) intermediates, catalyze LPS conversion, and provide fast electronic/ionic diffusion kinetics. The ZnS/rGO/S cathode is further applied in pouch Li-S cells, demonstrating the practicability of sulfur cathodes with reduced polarization.