Influence of Zinc Additive and pH on Electrochemical Behaviour of β-Nickel Hydroxide in Nickel Based Secondary Batteries

摘要

Nickel(II) hydroxide has been prepared by co-precipitation method with various concentrations of Zn additives (2,4,6 and 8 wt %) under different pHs (8, 9, 10 and 11). The elemental composition of zinc substituted nickel hydroxide samples were studied using energy dispersive X-ray analysis and the P-form of Ni(OH)2 samples were confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The interlayer distance (c0)) is found to expand with an increase in the percentage of zinc additives. The amount of SO4~(2-), CO3~(2-) and H:0 adsorbed by the crystals and the thermal stability of β-Ni(OH)2 are dependent on the pH. Under relatively high pH value, the synthesized nickel hydroxide materials possess an increasing degree of order and crystallinity, lower thermal stability, lower taping density and higher Ni composition. The electrochemical properties of the synthesized Ni(OH)2 materials were analyzed using cyclic voltammetry and electrochemical impedance spectroscopy. Jt is evident from the experimental data that the redox reactions exhibit quasi-reversible nature for all electrodes except for electrode C indicating that the charge and discharge process of the latter showed better reversibility compared to other electrodes. The electrochemical studies also indicate that zinc-ion additive is successful in increasing the reversibility of the electrode reaction and also the capacitance of the electrode.