Preparation Of Carbon-based Transition Metal Compound Composites And Its Electrochemical Performance

As an efficient energy storage device between lithium batteries and traditional capacitors,supercapacitors have the advantages of power density,fast charge and discharge,excellent cycle performance,long service life,and environmental friendliness.It plays an important role in chemical and aerospace.At present,commercial supercapacitors mainly use carbon materials as electrodes,but their energy density loss is difficult to meet the demand for high energy density.Therefore,how to further increase the energy density of electrode materials based on carbon materials is the key to be an urgently addressed problem.This article mainly takes porous carbon materials and carbon-based transition metal compounds as research objects and explores their preparation methods and electrochemical performance when used as electrode materials.By analyzing the electrochemical performance when it is used as an electrode material,the following relevant conclusions are drawn:1.Using glucose as the carbon source and trans-1,2-cyclohexanediaminetetraacetic acid?CDTA?as the nitrogen source,a three-dimensional nitrogen-doped porous carbon material was prepared by hydrothermal method and KOH activation method.The porous carbon electrode has good electrochemical performance and cycle stability.The specific capacitance is as high as 423 F/g at a current density of 0.5 A/g,and the specific capacitance is maintained after 5000 cycles at a current density of 10 A/g.The rate is still 92.5%.Besides,in the DLC301 electrolyte,asymmetrical supercapacitor based on porous carbon material has a current density of 58.75 Wh/kg and a power density of 250 W/kg.Connecting two assembled supercapacitors in series can make the driving recorder work normally for 15 s.This shows that honeycomb three-dimensional porous carbon is expected to be used as an electrode material for supercapacitors in specific devices.2.High conductivity NiCo₂S₄?NCS?nanosheets in situ grown in porous nitrogen-doped reduced graphene oxide?PN-r GO?materials were successfully prepared via a simple hydrothermal method.A synergistic effect between the NCS and PN-r GO matrix is observed on the electrochemical performance of the composites.PN-r GO/NCS exhibits an equivalent ultralow solution resistance?0.16??,ultrahigh specific capacitance?1687 F/g at a current density of 0.5 A/g?,and an excellent rate capability?1478 F/g at a current density of 10 A/g?.The asymmetric supercapacitor?ASC?is designed with PN-r GO/NCS as the positive electrode and activated carbon as the negative electrode.The ASC device exhibits a high capacitance?355.5 F/g at a current density of 1 A/g?.Density functional theory calculations show PN-r GO/NCS to increase the electrical conductivity of the material,and concomitantly the electrochemical performance.The data suggest that the PN-r GO/NCS hybrid structure can be considered as a future supercapacitor electrode material.3.A composite of FeCo₂S₄ nanoneedle and CC?FeCo₂S₄@CC?as successfully prepared by a two-step hydrothermal method.The composite material uses carbon cloth as the substrate,and nano needle-shaped FeCo₂S₄ is arrayed thereon,which effectively improves the charge transfer rate of the material.The needle-shaped FeCo₂S₄ is in good contact with the electrolyte,providing more active sites and making the material A more complete redox reaction occurs.The specific capacitance of the material at a current density of 0.5 A/g is as high as 1142 F/g.The specific capacitance is still maintained at 806 F/g at a current density of 10 A/g,which shows that the material has a good rate of magnification.With FeCo₂S₄@CC as the positive electrode and NPC as the negative electrode,the prepared ASC has a maximum energy density of 35.2 Wh/kg and a power density of 850.5 W/kg and exhibits excellent cycle stability.