Preparation And Properties Of Nickel Silicate Core-shell Microspheres/graphene Electrode Materials

Supercapacitors have the advantages of quick charge and discharge,low carbon and environmental protection,good reversibility,high power density,long cycle life,etc.They are one of the important means to solve energy shortage and environmental pollution,and have been widely concerned and analyzed.Nickel silicate is a potential electrode material for ultracapacitors due to its wide distribution,abundant resources,good oxidation reduction and good chemical stability.Therefore,nickel silicate is used as the electrode material for ultracapacitors in this paper.The phase and morphology of the electrode material were characterized by XRD,SEM,TEM and nitrogen adsorption-desorption experiments,and the electrochemical properties of the electrode material were studied by cyclic voltammetry test,constant current charge and discharge test,ac impedance test and cyclic life test.The research contents of this paper are as follows:1.Nickel silicate core-shell microsphere electrode materialThis paper adopts the St(?)ber prepared monodisperse,particle size uniform,silica ball is about 480 nm in diameter,using simple hydrothermal method with silica ball as silicon source and template preparation is about 525 nm in diameter nickel silicate core-shell microspheres(SiNiOH core-shell microspheres)electrode materials.A series of physical characteristics show that the prepared nickel silicate core-shell microspheres have poor crystallinity and clear core-shell structure,and the shell layer is composed of curved or folded nickel silicate nanosheets.The layered and porous structure facilitates the rapid transmission of ions and electrons.A series of electrochemical experiments were carried out for the research and analysis.The nickel silicate core-shell microspheres have good electrochemical properties,and the specific capacitance can reach 356.7 F/g at the current density of 0.5 A/g.After 5000 consecutive cycles,the capacitance retention rate is close to 92.5%.2.Nickel silicate core-shell microsphere/graphene composite electrode materialThis paper adopts the St(?)ber method and improved Hummer method for the silica ball and graphite oxide,respectively.Nickel silicate core-shell microspheres/graphene(SiNiOH core-shell microspheres/RGO)composites were prepared by simple hydrothermal method under alkaline conditions.The nickel silicate core-shell microspheres were attached to the layered graphene sheet layer,forming the layered porous composite with distinct structure and large specific surface area.Through A series of electrochemical experiments,the specific capacitance can reach 405.0 F/g at the current density of 0.5 A/g.By comparing the cyclic voltammetry curves of SiNiOH core-shell microspheres/RGO with those of SiNiOH core-shell microspheres under the scanning rate of 10 mV/s,and the specific capacitance and ac impedance maps corresponding to the same current density under different current densities,the results show that SiNiOH core-shell microspheres/RGO composites have greater capacitance capacity,better magnification performance and smaller resistance.Finally,SiNiOH core-shell microspheres /RGO were tested for cycle life at the current density of 5 A/g,and the specific capacitance retention rate was 98.27% after 5000 charge and discharge cycles.The research shows that SiNiOH core-shell microspheres is a kind of supercapacitor electrode material with adjustable structure,low cost,simple preparation and good electrochemical performance.After the combination with graphene,the multiplier performance is excellent,which further improves the rate and capacity of energy storage and has great potential and good application prospect.