Flower‐like NiO with a Hierarchical and Mesoporous Structure for Supercapacitors

Abstract

Abstract Hierarchical porous nickel oxide (NiO) has been synthesized through an ethanol‐based hydrothermal method followed by a sintering process. The effects of hydrothermal duration on morphology, crystalline structure, and electrochemical performance are studied. With the prolongation of hydrothermal duration, the as‐prepared NiOs appear in the form of scattered nanoflakes, then flower‐like porous balls, and then solid microballs. In this period, poly‐crystallization and re‐crystallization are observed successively. It seems 120 minutes is suitable to form hierarchical NiO, 2 μm mesoporous balls composed of nanoflakes in all directions. The duration shows significant influence on charge‐storage characteristics including reversibility, capacitance, and cyclic stability. The sample exhibits 678.4 F/g at 1 A/g discharge current density and maintains 94.8 % retention after 5000 cycles, suggesting a great prospect of the hierarchical NiO to be used as an electrode material for supercapacitors.