Defect Engineering in CuS_{1- x} Nanoflowers Enables Low-Overpotential and Long-Cycle-Life of Lithium-Oxygen Batteries

The defect engineering is essential for the development of efficient cathode catalysts for lithium-oxygen batteries. Herein, CuS_{1 -x} nanoflowers are fabricated by microwave hydrothermal method. Through theoretical and experimental analysis, the S vacancies are observed, which result in augmented charge around Cu, improved adsorption of LiO_2, and reduced overpotential. On the one hand, the generated electronic defects cause the Fermi level to shift toward the conduction band, which enhances the electronic conductivity and ion transfer. On the other hand, the increased S vacancies provide a large number of Cu active sites, which increase the charge transfer from Cu to LiO₂, which improves the stability of the intermediate adsorption. Interactively, CuS_{1- x} catalyst obtains a capacity of 23,227 mAh g^-1 and a cycle life of 225 at 500 mA g^-1. This work will be helpful for obtaining an efficient cathode catalyst by providing a deep understanding of vacancy modulation in advanced catalysts.