Preparation Of Co-Mn-C Composites By Electrostatic Spinning And Its Application In Asymmetric Supercapacitors

The increasing environmental pollution makes people speed up the pace of looking for green,clean and sustainable energy.In the current clean energy energy storage system,supercapacitors have been widely concerned by researchers due to their high energy density and long cycle life.Electrode materials is a key factor affecting the performance of supercapacitors.The development of high-performance electrode materials is a hotspot and future development direction of the current supercapacitor industry.At present,there are three main types of supercapacitor electrode materials commonly used:carbon materials,conductive polymers,and transition metal oxides.Transition metal oxides have attracted more and more researchers’ attention due to their higher theoretical specific capacitance.In this paper,porous carbon nanofibers and cobalt-manganese carbon ternary nanocomposites were prepared by electrospinning technique and subsequent high temperature treatment.The structure of the prepared materials was characterized by scanning electron microscopy(SEM),thermogravimetric analysis(TGA),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).The results show that:(a)the prepared porous carbon nanofiber has a specific surface area of 233 m2/g(much higher than that of pure carbon fiber 32 m2/g),and shows excellent electrochemical performance with a specific capacitance of 243 F/g at a current density of 1A/g(b)the latter prepared composites are Co4O3,MnO,C ternary nanocomposites,in which Co4O3 and MnO nanoparticles are uniformly distributed on carbon fibers.The electrochemical properties of the nanocomposite(CMC-X)were tested by cyclic voltammetry,constant current charge and discharge,and electrochemical impedance in a three-electrode system.The specific capacitance of CMC-2(molar ratio of cobalt acetate and manganese acetate was 1:2)reached 1052F/g(1A/g)and showed an excellent cyclic stability(capacitance retention rate was 96.7%after 1000 cycles).The electrochemical performance of the CMC-2//CNF-20 asymmetric supercapacitor was tested in 2 M KOH electrolyte with CMC-2 as the positive electrode and CNF-20(activated carbon nanofibers)as the negative electrode.This asymmetric supercapacitor delivered a capacitance of 116.2 F/g at 1 A/g and demonstrated long-term stability with a slight decrease over 1000 cycles.Furthermore,a high energy density of 36.3 Wh/kg can be obtained at a power density of 751 W/kg.