Flower-like NiO microspheres prepared by facile method as supercapacitor electrodes

Hierarchical flower-like NiO microsphere was successfully synthesized by a simple one-step template-free hydrothermal process, using l-lysine as precipitator and nickel sulfate as nickel source. The as-synthesized materials were characterized by X-ray diffraction, field emission scanning electron microscope, high-resolution transmission electron microscope, and the electrochemical workstation. The electrochemical results show that the flower-like NiO microspheres exhibit specific capacitance as large as 324 F?g^?1 at the current density of 2 A?g^?1 and the specific capacitance retention can maintain 83 % after 1,000 cycles at the current density of 20 A?g^?1 in 6 M KOH.