Nickel Hydroxide Modified And Its Electrochemical Capacitance Performance Research

Super-capacitor is a new kind of energy storage devices with high power density, high energy density, high charge-discharge efficiency,excellent reversibility,long cyclic performance and non-pollution. Ni?OH?₂ is a very promising electrode material because of its rather high theoretical capacity as well as low cost, but the low electronic conductivity,which limits the cycling performance of the material. In this study, Ni?OH?₂ directly grown on nickel foam were prepared via an in situ method. Their structure,composition, surface morphology and electrochemical performance are characterized by X-ray diffraction?XRD?, scanning electron microscopy ?SEM?, energy dispersive spectrometer ?EDS?,transmission electron microscopy ?TEM?, cyclic voltammetry ?CV?, electrochemical impedance spectroscopy ?EIS? and galvanostatic discharge-charge test to study the effects of Co additive and surfactant.The obtained Co_xNi_1-x?OH?₂ ?x=0.05, 0.10, 0.15, 0.20? composite electrodes were pure phase with no crystal change. The crystallization of the material turn to weak with the content of Co increasing. The morphology of Co_xNi_1-x?OH?₂ ?x=0.05, 0.10, 0.15, 0.20? is not sphere,which is different from ?-Ni?OH?₂. But both of them were compose of flake-like nanosheet. EDS analysis indicated that the practical contents of Co and Ni in Co_xNi_1-x?OH?₂ were in accordance with theoretical calculation. The results show that the Co_0.10Ni_0.15?OH?₂ composite electrode exhibits a drastic improvement in the capacitive characteristics of ?-Ni?OH?₂ with a specific capacitance increase from 386.4 to 1082.6 F·g-1 at a high discharging current density of 6 A·g-1. This work suggests that the as-prepared Co_0.15Ni_0.85?OH?₂ composite electrode has a promising future as higher charging/discharging rate materials for pseudo-supercapacitors.By adding different surfactants of SDBS, CTAB or PVP in the growth solution to study the influence on the physical properties and electrochemical properties of the material. The ?-Ni?OH?₂ electrode obtained in the presence of CTAB exhibited the best electrochemical reversibility and the highest specific capacity. Therefore, CTAB was chose as surfactant for further investigation.Cetyltrimethylammonium bromide ?CTAB? was used as surfactants to modify the crystallization of ?-Ni?OH?₂ via a simple template-free growth process onto nickel foam by using a mixed aqueous solution of nickel nitrate, CTAB and ammonia. Their structure and surface morphology are characterized by X-ray diffraction and scanning electron microscopy. The SEM images show changes in the microstructure of ?-Ni?OH?₂ and the XRD patterns exhibit a much higher relative diffraction intensity of ?100? peaks with the addition of CTAB. The effects of CTAB content on the electrochemical behaviors of?-Ni?OH?₂ are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results demonstrate that the modified?-Ni?OH?₂ electrode has better electrochemical performance, such as better reaction reversibility, higher proton diffuse coefficient, higher specific capacity, and better cyclic stability. Importantly, when the CTAB content in the initial solution was 0.03 g, the results show a drastic improvement in the capacitive characteristics of ?-Ni?OH?₂ with a specific capacitance increases from 386.4 to 1019.4 F·g-1 at a high charging/discharging current density of 6 A·g-1.