Study On Graphitized Porous Carbon Confined Co-Ni Compounds For Supercapacitors

Supercapacitors have got much attention due to their high power density,excellent cycle stability,and low cost.Compared with other types of capacitors,hybrid supercapacitors have more development potential.It not only has the characteristics of electric double-layer capacitors,but also has the advantages of tritium capacitors,which can obtain high power density and energy density at the same time to meet the needs of practical applications.In this thesis,according to the coupling mechanism between transition metal compounds and the synergy with the substrate material,transition-metal oxygen?sulfide?composites with different morphologies were designed and synthesized by several methods for the research of electrode materials for supercapacitors.These are used in supercapacitors research and show the excellent performance.The specific contents are as follows:?1?Ni-doped graphene loaded with gold nanoparticles was prepared by the sol method.After mixing it with ZIF-67,the Au NPs/NGO@Co₃O₄ was prepared by pyrolysis.Among them,the addition of gold nanoparticles improves the conductivity of the material,and Au as an electron donor increases the electron transport ability and improves the performance of the material.When the current density is 1 A g^-1,the nanocomposites exhibited a specific capacitance of 471.1 F g^-1.After 3000 cycles,the retention rate is 91%.?2?Graphene was used to optimize the structure of the polymer,and graphene-dispersed chitosan hydrogel was used as a precursor to fabricate the porous carbon.Highly uniform Co-Ni oxide nanoparticle-loaded B,N-doped hierarchical graphitic porous carbon was prepared through a dual pyrolysis process.The addition of graphene effectively increases the specific surface area of porous carbon materials,and the metal oxides increases the graphitization of porous carbon,thereby further optimizing the performance of the composite material.The composite materials exhibit high specific capacitance and excellent stability.The composites demonstrate a high capacitance of1266.7 F g^-1at 1 A g^-1.?3?Combining electrospinning technology and solvothermal method,a carbon fiber-supported cocoon-shaped core-shell-micelle NiCo₂O₄composite was prepared.This core-shell-micelle structure not only increased the surface area and facilitated close contact with the electrolyte,but also improved the ion transfer rates.The obtained NiCo₂O₄@C working electrode shows a high specific capacitance of 2000.6 F g^-1 at 1 A g^-1.Asymmetric supercapacitor cell assembled with reduced graphene oxide,which reached a maximum energy density of 61.2 Wh kg^-1 at a power density of 548.6 W kg^-1,and it shows well cycle stability.?4?The NiCo₂S₄ nanoneedle array was grown on the surface of nickel foam.And the effects of different vulcanizing agent and vulcanizing times on the properties of Ni-Co sulfides were studied.In order to further improve the performance of the NiCo₂S₄material,the surface of the NiCo₂S₄ nanoneedle array is covered with a layer of polypyrrole?PPy?,which is beneficial to the transfer of ions and electrons and inhibits the volume expansion of NiCo₂S₄during the redox reactions,thereby improving the property of the material.The asymmetric battery device composed with AC can provide an energy density of 41.24 Wh kg^-1 at a power density of 402.15 W kg^-1.