Research On N/P Co-doped Carbon Material And Metal Oxide Composite Supercapacitor

Supercapacitors have the advantages of fast charging and discharging speed and high power density,but they have the disadvantage of low energy density.The Faraday oxidation-reduction reaction that occurs when metal oxides is used as electrode materials makes them have a higher specific capacity,so they are suitable as electrode materials for high-energy density supercapacitors.In addition,heteroatom-doped carbon materials have the advantage of better conductivity,so the research idea of this article is to use heteroatom-doped carbon materials as a buffer layer with metal oxides and metal hydroxides to prepare excellent performance electrode material.First,polyacrylonitrile is used as the carbon source and nitrogen source,and phosphoric acid is used as the phosphorus source,and a nitrogen/phosphorus co-doped carbon layer is coated on the foamed nickel by high-temperature carbonization.Subsequently,the active material was prepared on the carbon layer by hydrothermal method.The main research contents and results are as follows:By adjusting the mass ratio of polyacrylonitrile and phosphoric acid,it is found that when the mass ratio of the two is 20,the prepared nitrogen/phosphorus co-doped carbon layer(denoted as N/P-20)has the best performance.Through elemental analysis,it is found that the nitrogen in the carbon layer mainly exists in the form of pyrrole nitrogen and pyridine nitrogen,which are beneficial to the electrochemical activity of the electrode,while phosphoric acid mainly exists in the form of a functional group.Activated carbon is used as the negative electrode to assemble a water-based asymmetric supercapacitor.After cyclic voltammetry test,it is found that the voltage window has been expanded to 1.4V,which is mainly due to the presence of phosphorus in the carbon layer,which enlarges the reaction window of the electrode,which has a positive effect on increasing its energy density.Use ammonium fluoride and sodium lauryl sulfate as surfactants to control the composition of the precursor solution,and prepare Ni Co₂O₄ nanometers on pure foam nickel(Ni)and N/P-20 by hydrothermal method and high temperature annealing.sheet.Electrochemical tests show that when the current density increases from 5A/g to 50A/g,the specific capacity of Ni Co₂O₄@NP electrode remains at 62.5%,which is much higher than the45.5%of Ni Co₂O₄@Ni electrode;when the current density is 50A/g.After 5000 cycles of charging and discharging,the capacity retention rate of Ni Co₂O₄@NP electrode still reached89.3%.After calculating the capacitance contribution rate of the two electrodes at the same time,it is found that at a scanning speed of 50m V/s,the pseudocapacitance contribution rate of the Ni Co₂O₄@NP electrode reaches 91.7%,which is higher than the 73.7%of the Ni Co₂O₄@NF electrode.The excellent electrochemical performance of the Ni Co₂O₄@NP electrode is due to the presence of the carbon layer which improves the bonding strength between the active material and the current collector and the overall conductivity of the electrode material.Activated carbon is used as the negative active material to assemble an asymmetric supercapacitor.When the power density is 849.9W/kg,the energy density is61.9Wh/kg.And due to the effect of the phosphorus element in the carbon layer,the voltage window of the device is expanded to 1.7V,and the energy density of the device is improved.After 5000 cycles of cycle life tests at a current density of 20A/g,the capacity retention rate was 93.4%.The Ni(OH)₂-MnO₂ hybrid nanosheet composite was prepared by one-step solvothermal method as a supercapacitor cathode material.Through electrochemical testing,at a current density of 1A/g,the specific capacities of MnO₂@NP electrode,Ni(OH)₂@NP electrode and Ni(OH)₂-MnO₂@NP electrode are 188.9F/g,873.6F,and 1175.6F/g,respectively.When the current density increases from 1A/g to 20A/g,the rate performance of the Ni(OH)₂-MnO₂@NP electrode is 52.3%,and after 2000 cycles of charge and discharge at a current density of 10A/g,its specific capacity retention rate is still 75.3%,which is higher than the electrode of two single-component active materials.It can be found that the use of the synergistic effect of the two active materials increases the overall stability and conductivity of the electrode,and its impedance is lower than that of an electrode with a single-component active material.After being assembled with activated carbon to form an asymmetric supercapacitor,when the power density is 850W/kg,the energy density is 39Wh/kg,and the charge-discharge cycle is 2000 cycles at a current density of 10A/g.The specific capacitance retention rate of the device is the initial of 89.2%.