Synthesis and electrochemical properties of nickel oxide coated ZnMn₂O₄ nanocomposites

Abstract

Nickel oxide coated ZnMn₂O₄ nanocomposites were successfully synthesized by two-step method combined hydrothermal reaction and calcination process. The microstructure, morphology and the color mapping of the as-prepared samples were characterized by means of X-ray diffraction, high resolution electronic microscope microstructure, field emission scanning electron microscopy and energy-dispersive X-ray spectrum. The electrochemical performance of the samples were investigated by cyclic volt-ampere (CV), constant-current charge–discharge and electrochemical impedance spectroscopy. The experimental results show that nickel oxide coated ZnMn₂O₄ nanocomposites exhibit weak Ni₂O₃ hexagonal phase besides obvious ZnMn₂O₄ spinel tetragonal structure, the morphologies are uniform polyhedron structure with obvious cladding layer. CV curves exhibit rectangular shape without obvious redox peaks. Nickel oxide coated ZnMn₂O₄ nanocomposites shows better specific capacitance and excellent cyclic stability, and maintains 98.8% of its initial capacitance after 1200 cycles. Nyquist plots of nickel oxide coated ZnMn₂O₄ nanocomposites proving the samples possess lower resistance and ideal electron conductivity.