Microwave-assisted non-aqueous homogenous precipitation of nanoball-like mesoporous α-Ni(OH) ₂ as a precursor for NiO _x and its application as a pseudocapacitor

A novel facile and template-free method to prepare a nanoball-like NiO _x material has been developed. The preparation involves the synthesis of an α-Ni(OH) ₂ precursor by microwave heating and calcination of the precursor. The NiO _x material possesses a nanoball-like structure with a large surface area. The pseudo-capacitive properties of the NiO _x material were evaluated by cyclic voltammetry and electro-chemical impedance spectroscopy in 6 M KOH solution. The specific capacitances were 951, 796, 713 and 650 F g ^-1, corresponding to the scan rates of 2.0, 5.0, 10 and 20 mV s ^-1, respectively. The NiO _x material also showed excellent cycling stability and maintained 92% of its maximum specific capacitance after 1000 cycles. The hybrid supercapacitor based on this NiO _x material exhibited moderate energy density and power density.