Study On Preparation And Energy Storage Performance Of Graphene/Double Metal Hydroxide Composite

In recent years,as a kind of high theoretical capacity pseudocapacitance material,bimetallic hydroxide has aroused widespread interest of researchers.However,due to its poor conductivity caused by polymerization during charging and discharging,the low cycle efficiency has seriously affected its practical application in energy storage devices.In this paper,chemical vapor deposition（CVD）,hydrothermal synthesis and electrodeposition are used to prepare nickel-cobalt layered double hydroxides（Ni Co LDH）/graphene nanowalls（GWNs）/nickel foam（NF）composite electrode and nickel-cobalt hydroxide（NCH）/graphene（Gr）/nickel foam（NF）composite electrodes.Through scanning electron microscope,transmission electron microscope,X-ray diffractometer,Raman spectrometer,X-ray energy spectrometer and electrochemical workstation,the microstructure,chemical composition and electrochemical performance of the materials were characterized and analyzed,and its storage was discussed.The main research contents and results of energy mechanism and its application in supercapacitors are as follows:1.Graphene/nickel foam（Gr/NF）and graphene nanowall/nickel foam（GNWS/NF）materials with controllable layer number were prepared by chemical vapor deposition（CVD）and plasma-enhanced chemical vapor deposition（PECVD）techniques on the base of nickel foam,respectively.Both of them can be directly used as current collectors for capacitor materials.2.The graphene nanowalls/nickel foam（GWNs/NF）prepared by PECVD method is used as the substrate,and the nickel-cobalt layered double hydroxide/graphene nanowalls/nickel foam composite electrode is prepared by the electrodeposition method.The micromorphology of Ni Co LDH can be adjusted by adjusting the concentration of solution and electrodeposition time solution concentration,electrodeposition time and other parameters and the performance of the electrode was improved obviously.The Ni₁Co₂ LDH/GNWS/NF electrode exhibits a specific capacity of 2068.3 F g^-1 at the current density of 1 A g^-1,even the current density is magnified by 20 times,the specific capacity retention rate is about 77.4%.3.The nickel cobalt hydroxide/graphene/foam nickel composite electrode is prepared by hydrothermal reaction with Gr/NF as the substrate and the microscopic morphology of nickel cobalt hydroxide is adjusted by adding an appropriate amount of surfactant PVP.At the current density of 1 A g^-1,the prepared composite electrode has a specific capacity increased to 2854.9 F g^-1,and after 3000 cycles,the specific capacity retention rate is 81.3%,which shows the enhanced multiplier performance and good cycle stability.4.The composite electrode shows good electrochemical performance,and the enhancement mechanism is as follows:the self-supporting electrode system constructed by using the three-dimensional network structure of nickel foam not only provides a larger growth area,but also increases the contact with the electrolyte;Graphene prepared by CVD and PECVD has excellent electrical conductivity,which speeds up electron transmission and provides more transfer channels;The prepared bimetallic hydroxides have the morphology of nanosheets and more active sites in the process of charge and discharge.