Cobalt Oxide/Graphene Nanosheets/Hexagonal Boron Nitride (Co<sub>3</sub>O<sub>4</sub>/CoO/GNS/<i>h</i>-BN) Catalyst for High Sulfur Utilization in Li–S Batteries at Elevated Temperatures
Yasmin Mussa, Muhammad Arsalan, Edreese H. Alsharaeh
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.