Preparation And Electrochemical Properties Of Metal Oxide Supercapacitor Elecrode Materials

Electrode materials are the main factors affecting the electrochemical performance of supercapacitors.Nickel-cobalt-ferrum-based metal oxides,as a kind of electrode material with high theoretical capacity,low cost and environment-friendly,have been paid more and more attention by researchers.In this paper,one-dimensional nano-fiber supercapacitor electrode material with excellent performance was prepared by uniaxial and coaxial electrospinning process,with the aim of optimizing electrospinning process as the starting point,and one-dimensional metal oxide was prepared by uniaxial and coaxial electrospinning process.Binary metal oxide precursor nanofibers and Ni-Co-Fe-based core-shell composite metal oxide precursor nanofibers were prepared by heat treatment.The micromorphology and structure of the electrode materials were characterized by XRD,SEM,TEM and the electrochemical workstation was used to test the electrode with linear cyclic voltammetry,constant current charge-discharge and AC impedance measurements.Fe₂O₃,NiO,Co₃O₄ precursor was prepared by optimized electrospinning method,and then calcined at 600?to obtain NiO,Co₃O₄ and Fe₂O₃ nanofibers.The samples were characterized by XRD,SEM,TEM,which showed that the samples were pure phase crystals,and maintained a complete one-dimensional fiber and three-dimensional network structure.Cyclic voltammetry showed that all three materials had good redox reversibility.Constant current charge and discharge tests show that the specific capacitance of Fe₂O₃,NiO and Co₃O₄ is 160 Fg^-1,209 Fg^-1 and 211 Fg^-1,respectively,at the current density of 1Ag^-1.According to the composition analysis of electrode materials,Co₃O₄ shows the best performance,followed by NiO,and Fe₂O₃has more commercial value in terms of cost-performance.Pure NiFe₂O₄ and CoFe₂O₄ nanofibers were prepared by optimized electrospinning method.Cyclic voltammetry tests showed that both materials had good redox reversibility.Constant current charge and discharge tests show that NiFe₂O₄ is 286Fg^-1,and CoFe₂O₄ is305Fg^-1 at 1Ag^-1 current density.The specific capacity of binary NiFe₂O₄ and CoFe₂O₄ is higher than that of Fe₂O₃,NiO,Co₃O₄,which indicates that Ni-Fe and Co-Fe can co-increase the specific capacity.The multi-element metal oxides based on ferrum have better performance-price ratio.The NiFe₂O₄@CoFe₂O₄ core-shell composite nanofibers were prepared by self-made coaxial electrospinning device.The specific capacitance of the nanofibers reached 480 Fg^-1.After 2000 cycles at the current density of 5Ag^-1,the capacity of the nanofibers could be kept to 87%.It shows excellent cyclic stability.Compared with monofilament NiFe₂O₄,CoFe₂O₄,the core-shell composite structure NiFe₂O₄@CoFe₂O₄ can bring about synergistic effect,increase the reactive sites and increase the electron transfer rate,so that the electrochemical properties of the materials can be improved to a certain extent.