Nickel metal hydride (Ni/MH) batteries are presently as the promising high capacity power sources applied in the various portable electronic devices and the hybrid electric vehicles. After a Ni/MH battery was assembled, the forming process was carried out to assure its performances, which included the high charge/discharge capacity, the good cycle durability, and the low internal resistance. The effect of charging current, charging temperature, concentration of KOH, concentration of LiOH, soaking time, and soaking temperature on the formation of a Ni/MH battery was investigated in the present work. The experimental results indicate that the best utilization of the positive electrode is found to be 86.3% at the conditions of 0.2C charging current, 25 °C, 7.129 M KOH and 0.477 M LiOH for the battery soaked at 30 °C for 12 h. The electrochemical properties of Ni/MH battery are investigated by AC impedance, and the elements of equivalent circuit for various forming conditions are evaluated by using the complex nonlinear least square (CNLS) technique. The active material β-Ni(OH)2 in the positive electrode is transformed to β-NiOOH and γ-NiOOH in the forming process observed by the X-ray diffraction (XRD) analysis. When the soaking time and temperature of the forming process increase, the utilization of positive electrode increases due to the increase in its electroactive area and fraction of γ-NiOOH.
