Construction And Electrocemical Performance Of Cobalt-aluminum Hydroxide/Graphene/Ni Foam Electrode Materials For Supercapacitors

Recently,energy problems have become increasingly apparent,and supercapacitors have been considered as ideal new alternative energy sources due to their high efficiency charging and discharging,good stability for cycling,environmental friendly,safety and so on.Layered double hydroxides(LDH)is a hot spot in the study of pseudocapacitor electrode materials because it can simultaneously possess the characteristics of double electric layer capacitance and pseudocapacitance.However,the low conductivity of LDHs electrode material limits the electron transfer rate,which leads to the low performance under high charge discharge current density.Studies have shown that the combination of transition metal double hydroxides and carbon materials has a significant impact on the structure and electrochemical performance of electrode materials.In addition,the suitable base also plays a very important role.Nickel foam has the characteristics of high porosity,large specific surface area and unique three-dimensional network structure,which can provide large redox reaction,and the effective way of fast electron transmission between the active electric center and the current collector are presented.Nickel foam is widely used in electrode materials.In this paper,Co-Al LDH as the main research object,and compounding it with graphene can effectively reduce the degree of agglomeration and increase the specific capacitance of the composite material.Analyze and characterize the microscopic morphology and crystal structure of the composite material through SEM and XRD,and analyze its electrochemical performance through electrochemical testing.The main research contents are as follows:(1)The Co-Al LDH/Go composite was prepared by hydrothermal method.The nanosheet layered structure of the layered double metal hydroxide makes the material have a higher specific surface area.The addition of GO can promote the rapid electron transfer between the LDH and the current collector(foam nickel),and the higher electrochemical activity is mainly attributed to The Faraday redox reaction caused by the transformation of Co2+ and Co3+.According to the electrochemical test,the specific capacitance of Co-Al LDH/Go is obviously better than that of Co-Al LDH,and the addition of GO effectively improves the conductivity of the electrode material.(2)Explore the Co-Al LDH/Go composites prepared with different cobalt-aluminum ratios.The electrochemical test results show that the Co-Al LDH/GO composite prepared when n(Co2+):n(Al3+)=2:1 has a specific capacitance of 674.3F g-1 at a current density of 1A g-1.After 2000 cycles of the electrode material at a current density of 10 A g-1,its initial specific capacitance maintained 75%.Therefore,the excellent electrochemical performance of the Co-Al LDH/GO electrode material proves that the material is a potential supercapacitor electrode material.(3)Based on the consideration of the stability of the electrode material,the Co-Al LDH/r GO/NF composite material was prepared by a water bath and one-step hydrothermal method.SEM results show that a flower-like spherical structure connected by nanosheets is formed on the 3D NF framework.This structure is conducive to the transportation of charges and mass,reduces volume changes during charging and discharging,and improves the stability of electrode materials.At a current density of 1A g-1,the specific capacitance value of the Co-Al LDH/r GO/NF composite material is 1950 F g-1;after 5000 cycles of constant current charge and discharge test,the specific capacitance retention value is 81%.The construction of the composite material significantly improves the electrochemical performance of the electrode material.