Hydrothermal synthesis and electrochemical capacitor application of urchin-like NiCo2O4 particles: effect of urea concentrations

NiCo2O4-based materials are promising for high-performance energy storage materials. Here, we report the synthesis of urchin-like NiCo2O4 particles via the hydrothermal urea precipitation process, and studied the effect of urea concentrations on phase purity, microstructure, and electrochemical capacitor performance. NiCl2 center dot 6H(2)O, CoCl2 center dot 6H(2)O and urea, were weighed as Ni:Co:urea = 1:2:15, 10 or 151 in molar fraction, and they were dissolved in distilled water and hydrothermally heated at 140 degrees C for 6 h. The three precursors were calcined at 350 degrees C for 3 h in air atmosphere. The three products were mainly composed of 3-10 mu m sized urchin-like particles. All the final samples had 5-20 mu m sized mesopores and similar to 50-70 m(2)/g of specific surface area, but the distributions of Ni and Co in the urchin-like particles were affected by the starting urea concentration. The sample of single-phase NiCo2O4 from Ni:Co:urea = 1:2:15 showed the best electrochemical capacitor performance among the three urea concentrations. (C) 2019 The Ceramic Society of Japan. All rights reserved.