Synthesis and characterization of active materials of Ni(OH)2 powders

The positive electrode active materials of Ni(OH)2 powders for alkaline Ni-MH battery have been fabricated by a chemical precipitation (CP) method. The characteristic properties of CP-Ni(OH)2 powders were analyzed by the SEM, XRD, and AAS. The electrochemical properties of Ni(OH)2 powders, such as capacity density, charge efficiency, percent of utilization, and impedance, etc., have been systematically investigated. The electrochemical properties of Ni(OH)2 powders were also analyzed by the galvanostatic charge-discharge test and AC impedance spectroscopy. It was observed that the electrochemical properties of nickel cathodes depend on the types of powders, i.e., they are dependent on the preparation conditions, types of conductive materials, discharge rates, and state of discharges (SODs). In general, it must be noted that a nickel hydroxide electrode with the addition of cobalt oxide shows much better electrochemical properties. Those characteristic properties of CP-Ni(OH)2 powders are compared to the commercial high-density spherical Ni(OH)2 powders. It was experimentally observed that the optimum preparation conditions for preparation of Ni(OH)2 powders are as follows: 1.5 M nickel salt concentration (NiSO4); temperature of 60°C; a reaction pH value of 13; 2 M NaOH concentration and dried at 110°C. The Ni-MH batteries prepared by CP Ni(OH)2 powders have been assembled and tested. The electrochemical characteristics of the Ni-MH batteries were examined. It was indicated that the Ni-MH batteries have good performance of charge and discharge characteristics.