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In this study, the co-precipitated Co-Ni(OH)2 and Zn-Ni(OH)2 with different concentration of cobalt and zinc ions have been made by a chemical precipitation method. The characteristic properties of Ni(OH)2 powders were analyzed by the XRD and DTA-TGA methods. The electrochemical properties of Ni(OH) have been investigated. It was observed that a full | Journal of Chemistry Vol. 44 3 P. 387 - 391 2006 INFLUENCE OF COBALT AND ZINC iON ADDITION ON THE STRUCTURE AND ELECTROCHEMICAL BEHAVIOUR OF NICKEL HYDROXIDE Received 30 May 2005 NGUyEN THI CAM HA TRINH XUAN SEN NGUyEN XUAN VIET Faculty of Chemistry Hanoi University of Science VNU SUMMARY In this study the co-precipitated Co-Ni OH 2 and Zn-Ni OH 2 with different concentration of cobalt and zinc ions have been made by a chemical precipitation method. The characteristic properties of Ni OH 2 powders were analyzed by the XRD and DTA-TGA methods. The electrochemical properties of Ni OH 2 have been investigated. It was observed that a full transformation from 3-Ni OH 2 phase to a-Ni OH 2 one had occurred after the content of zinc reached 25 mol . Cyclic voltammetric studies indicated that the Ni OH 2 containing cobalt and zinc ions exhibited better reversibility and convertibility for the Ni OH 2 NiOOH redox reactions than those of pure Ni OH 2 electrode. I - INTRODUCTION Nickel hydroxide is widely used as an active material in nickel electrode. The high power density very good cyclability and high specific energy of these electrodes make them very competitive for an extended range of applications 1 2 . In current designs of rechargeable batteries containing nickel electrode the battery capacity is generally limited by nickel electrode for reasons of battery safety 3 4 . It is obvious that the increase of the energy density of nickel hydroxide electrode is essential to raise the energy density of such batteries. In the some references 3 6 8 it is reported that there are four phases existing over the lifetime of a nickel hydroxide electrode they were namely P-Ni OH 2 P-NiOOH y-NiOOH and a-Ni OH 2. The formation of y-NiOOH can be associated with the volume expansion or swelling of the nickel hydroxide electrode. The expansion of the active material interfered with the effective contact between particles of the active material and this phenomenon increased the resistance .
