Cobalt Oxide/Graphene Nanosheets/Hexagonal Boron Nitride (Co3O4/CoO/GNS/h-BN) Catalyst for High Sulfur Utilization in Li–S Batteries at Elevated Temperatures

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.