Graphene quantum dot-modified Co3O4/NiCo2O4 yolk–shell polyhedrons as a polysulfide-adsorptive sulfur host for lithium–sulfur batteries

Abstract

The shuttle effect of lithium polysulfides and non-ideal reaction kinetics restrict the development of high-energy-density lithium–sulfur (Li–S) batteries. Here, we report a graphene quantum dot (GQD)-modified Co₃O₄/NiCo₂O₄ yolk–shell polyhedron as a sulfur host for Li–S batteries. GQDs shorten transport pathways of electrons, while strong binding of Co₃O₄ and NiCo₂O₄ to Li₂S₄, Li₂S₆ and Li₂S₈ are demonstrated from density functional theory calculations. Co₃O₄/NiCo₂O₄/GQDs@S shows a high capacity of 727 mA h g⁻¹ after 100 cycles, along with a well-recoverable rate performance. A good tolerance at low temperature of −5 °C is also achieved, enabling a potential for applications in various conditions.