The Research Of Polyacrylonitrile-based Carbon Material And Metal Sulfides Composite Supercapacitor

Supercapacitors can realize quick storage and release of electric energy,and make up for the gap between traditional capacitor and battery.Recent studies have found that metal sulfide has high conductivity and specific capacity,so it is more suitable for the preparation of super capacitors with high energy density.However,higher energy density must rely on electrode for redox reaction,how to guarantee the high energy density under the premise of improving the stability of the electrode,has always been the difficulty.Therefore,this paper used the conventional nickel foam as the collecting fluid,and the graphite buffer layer of nitrogen doping is prepared by high temperature pyrolysis polyacrylonitrile fiber on the surface of foam nickel.The testing results show that after treated at 800°C for 1 hour,the graphite layer revealed good thermal stability.The content of N element content was 11.48%,and it was in the form of pyrrole and pyridine nitrogen.At the same time,the surface of the graphite layer is distributed with porous structure,and the stomatal structure starts from the junction of three grains with more defects,and then spreads to the whole grain surface.Based on solvent thermal method,CuCo₂S₄ active material was prepared on pure nickel foam?Ni?current collector surface and a current collector coated with nitrogen doped graphite layer?NG?.After electrochemical testing,the specific capacitance of the CuCo₂S₄@NG electrode was 1508 F/g at the current density of 5 A/g,which was higher than 1443 F/g of CuCo2S4@Ni electrode.In the process of increasing the current density from 5 A/g to 50A/g,the CuCo₂S₄@NG electrode capacitance remained at 61.6%,higher than the 32.1%of CuCo₂S₄@Ni electrode.After cycling 2000 times in the current density of 50 A/g,the retention of CuCo2S4@NG electrode was 85.3%,higher than 59.4%of CuCo2S4@Ni electrode.The assembled CuCo₂S₄@NG//rGO asymmetric super capacitor exhibited a power density of 58.4 Wh/kg at the power density of 797 W/kg.After 5000 cycles at a current density of 10 A/g,the capacitance retention was maintained at 97.5%of the initial value.The researches of faraday pseudocapacitance active material were mainly focused on the transition metal elements.The research of semiconductor is seldom,and the composite of transition metal and semiconductor was less.Therefore,in order to fill the vacancy of relevant research content,it is very important to study the synergy between the two metals.In this paper Ni foam coated by nitrogen doped graphite layer was used as the current collector.CdS@NG electrodes were synthesized in the glycerol and polyvinylpyrrolidone mixed solvent.MnO₂ whiskers were added to increase the energy density and stability of the electrode.The test results show that the specific capacitance of MnO₂-CdS@NG electrode is 1502F/g at the discharge current density of 2 A/g,which is higher than 1247 F/g of the CdS@NG electrode.In the process of increasing the current density from 2 A/g to 50 A/g,the capacitance of MnO₂-CdS@NG electrodes remained 52.1%,higher than the 48.1%of the CdS@NG electrode.After 1000 cycles at a current density of 10 A/g,the retention of MnO₂-CdS@NG electrode was 81.7%,higher than 51.1%of the CdS@NG electrode.Obviously,MnO₂-CdS@NG electrode shows higher activity and stability due to the existence of MnO₂ whisker.After being assembled with the rGO electrode,the MnO₂-CdS@NG//rGO asymmetric super capacitor has a power density of 33.8 Wh/kg at the power density of 776 W/kg.After 5000 cycles at the current density of 10 A/g,the capacitance retention was 87%of the initial value.