Study On Energy Storage Performance Of Multi Nickel Cobalt Based Electrode Materials

Supercapacitors stand out among new energy storage devices because of their fast charge and discharge speed,strong stability and high power density.As the decisive factor of supercapacitor performance,supercapacitor electrode materials have always been the focus of research.Among many supercapacitor electrode materials,transition metal compound electrode materials have more active pseudo-capacitance reaction.Ni and Co have high content,low cost and variable valence in nature,and they have synergistic effect when they exist together.Their compounds are ideal electrode materials,but their disadvantages such as poor conductivity and obvious volume expansion limit their application.In this paper,several representative nickel and cobalt compounds are used:Nickel-cobalt oxide,nickel-cobalt phosphate,nickel-cobalt sulfide and nickel-cobalt hydroxide are the main research objects,which are compounded with carbon materials,and then the supercapacitor performance of the composite materials is studied and discussed.The research contents are as follows:(1)Study on the performance of NiCo₂O₄ composite supercapacitors coated with graphene oxide by electrodeposition reduction.The NiCo₂O₄ in NiCo₂O₄@r GO grows uniformly on nickel foam,and the surface is covered with a layer of graphene,which can increase the conductivity of the composite.The wrinkle structure on the surface can increase the contact area between the material and electrolyte,and can also be used as a buffer to slow down the volume expansion of NiCo₂O₄.The reduced graphene oxide coated NiCo₂O₄ composite has a specific capacitance of920.2 F g^-1 at the current density of 1 A g^-1.(2)Study on the performance of Ni-Co-phosphate composite supercapacitors coated with graphene oxide by in-situ growth reduction.In NCPO@r GO electrode materials,graphene covers Ni3(PO4)2·8H2O and Co3(PO4)2·8H2O to form a unique sandwich structure,which grows on nickel foam.Graphene directly establishes more and faster electron transmission channels between foam nickel and phosphate,which enhances the conductivity of the composite,and the coating structure can also weaken the volume expansion of nickel cobalt phosphate.Under the current density of 1 A g^-1,the specific capacitance and surface capacitance of the in-situ grown reduced graphene oxide coated nickel cobalt phosphate electrode material reached 1416.7 F g^-1and 3.69 F cm².(3)The acidified carbon nanotubes were wound on the surface of Co9S8,and then embedded in NiCo LDH by a two-step hydrothermal method,so as to prepare the Co9S8-a CNT-NiCo LDH composite material and apply it to supercapacitors.Co9S8-a CNT-NiCo LDH presents a unique mosaic structure.NiCo LDH,as a mosaic matrix,can provide higher specific capacitance contribution and has larger specific surface area.Embedded with hollow Co9S8,It can connect the inside and outside of the material to provide more ion transmission channels;ACNT winding Co9S8 can not only improve the conductivity,but also reduce the volume expansion of Co9S8.The specific capacitance of nicoldh composite was1121.4 F g^-1 at 1 A g^-1 current density.