Abstract
The high theoretical energy density and low cost of lithium–sulfur (Li–S) batteries make them promising candidates for future energy storage devices. Here, we developed Co3O4/CoO/graphene nanosheets (GNS)/hexagonal boron nitride (h-BN) nanocomposite-based sulfur as cathodes for Li–S batteries. Due to the synergistic effects of GNS/h-BN and Co3O4/CoO, the reported Co3O4/CoO/GNS/h-BN nanocomposites not only effectively trap lithium polysulfides but also can accelerate the redox kinetics for the conversion of polysulfides. The enhanced electrochemical activity of Co3O4/CoO/GNS/h-BN is due to the (111) exposed surface of Co3O4 and the formation of CoO on Co3O4, which is the catalytically active phase of Co3O4-based catalysts. GNS/h-BN provides a large surface area for the high exposure of the Co3O4/CoO catalyst and can also influence the catalytic activity due to enhanced charge transfer. Co3O4/CoO/GNS/h-BN/S nanocomposites showed superior electrochemical performances and high sulfur utilization compared to GNS/h-BN/S and Co3O4/CoO/S. More significantly, a very high capacity retention of 89% was obtained with a reversible capacity of 356.29 mA h/g after 250 cycles at a current rate of 1 C. Also, enhanced redox conversion of lithium polysulfides was observed when the cell was operated at higher temperatures. Besides cobalt oxide, other metal oxides such as Fe2O3 and SnO2 on GNS/h-BN could also be potential candidates for high-performance Li–S batteries.