Optimizing oxygen vacancies can improve the lithium storage properties in NiO porous nanosheet anodes

NiO porous nanosheets were synthesized by a facile hydrothermal reaction and subsequent calcination in air. Oxygen vacancies were generated by reducing treatment under H2/Ar atmosphere at an elevated temperature. The phase composition, morphology, microstructure and chemical composition of the samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). When used as the anode materials for lithium ion batteries, the optimized NiO electrode possessed a reversible capacity of 678.8 mAh g−1 after 30 cycles at a current density of 0.1 A g−1, while the reversible capacity of the untreated electrode was only 82.5 mAh g−1. At a higher current density of 1.0 A g−1, the reversible capacity was 152.2 mAh g−1, which is 15 times larger than that of the pristine NiO electrode. The synergistic effects of optimized oxygen vacancies and porous sheet-like morphology are responsible for the enhanced lithium storage properties.