Realizing the growth of nano-network Li2O2 film on defect-rich holey Co9S8 nanosheets for Li-O2 battery

Confining and controlling the growth of discharge products through favorable nanostructures of the solid catalysts to realize the formation of nanoscale Li2O2 is an effective strategy to reach both high capacity and good reversibility of Li-O-2 battery. However, utilizing the nanostructures of the transition metal-based catalysts to realize the deposition of nanoscale Li2O2 is still a challenge. In this work, defect-rich holey 2D Co9S8 nanosheets (H-2D-Co9S8) were firstly synthesized and acted as the cathode catalyst of Li-O2 batteries. The 2D architecture and in-plane holes of the catalyst not only facilitate mass transfer, but also provide the rich sulfur deficiency as active sites. The favorable nanostructure of H-2D-Co9S8 could induce the formation of loose and thick discharge product film constructed by discrete nanoscale Li2O2, which offer a higher capacity (3500 mAh/g based on the total mass of catalyst (70%) and KB (20%)) compared with that of the bulk film-like Li2O2 on the bulk Co9S8. More importantly, the discrete nanoscale Li2O2 could be decomposed more easily because of the improved charge transport and delithiation property derived from its smaller particle size and higher surface area, thus leading to better reversibility of the battery (100 cycles at a limited capacity of 500 mAhg(-1)). This work provided some new insights into achieving the improvement of the Li-O-2 battery performance through confining and controlling the deposition of nanoscale Li2O2 by the favorable nanostructures of the transition metal-based catalysts.