Study On Controllable Preparation And Electrochemical Properties Of Nickel Cobalt Based Electrode Materials

In recent decades,with the increasingly severe challenges of energy crisis and environmental problems in the world,the market demand for high-performance energy storage systems and devices is growing.As one of the most promising clean energy storage devices,supercapacitor has been widely concerned.Among all kinds of energy storage systems,supercapacitor is considered as a potential green and efficient energy storage system because of its high power density,long cycle life,fast charging and discharging speed and good safety.In order to construct high performance nickel cobalt based electrode materials,a low-cost and easily available natural porous diatomite(DE)was designed NiCo-LDH@DE?NiCo-OH@DE and NiCo S@DE.The relationship between morphology,composition,crystal structure and electrochemical performance was discussed.(1)In this work,the design of NiCo-LDH@DE in the composite,NiCo-LDH nanosheets were dispersed on the de substrate to form a network structure on the de substrate,which shortens the ion electron migration path in the process of electrochemical reaction.By adjusting the molar ratio of Nito CO,the best NiCo-LDH@DE samples were obtained,When the molar ratio of Ni/CO is 2,Ni₂Co₁-LDH@DE has a medium crystallinity and a suitable interlayer spacing and shows the best performance.The specific capacitance is 163.25 F g^-1at 1 A g^-1,and120 F g^-1at 15 A g^-1.(2)In order to investigate the effect of morphology on nickel cobalt hydroxides,nanowire like nickel cobalt hydroxides were constructed(NiCo-OH@DE).The experimental results show that the nickel cobalt hydroxide with nano wire morphology has a larger specific surface area.Subsequently,the effect of crystal structure and specific surface area on the electrochemical performance was investigated by adjusting the molar ratio of Ni/CO.it was found that Ni₃Co₁-OH@DE exhibited the best electrochemical performance.The specific capacitance reached 769.2 F g^-1at 1 A g^-1,and the rate performance reached 82.9%when the current increased to 15 A g^-1.(3)After sulfurization reaction of the nickel cobalt hydroxides@DE,the crystal phase transformation was realized and different structures NiCo S@DE were formed.It was found that the Ni₂Co₁S@DE,which possessed nanowire morphology and single-phase structure,showed the best comprehensive electrochemical performance shows the best performance sample,the specific capacitance is 918.3 F g^-1at 1 A g^-1,and still has 82.6%of the original specific capacitance after 2000 times of charge and discharge at 15 A g^-1.The overall performance of Ni₂Co₁S@DE//AG ASC is limited by the anode material AG,and its energy density is still up to 24 Wh kg^-1when the power density is 697 W kg^-1.