Effect of nickel hydroxide composition on the electrochemical performance of spherical Ni(OH)2 positive materials for Ni–MH batteries

A special method “conduit synthesis technology” has been utilized to produce spherical nickel hydroxide powders with different chemical compositions. Three kinds of powers A, B, C were prepared by chemically coprecipitating Ni, Co, Zn, Ca, Mg and Cu. It was found that powder B produced better performance than the others. The discharge capacities of powder B could achieve 280 mAh g−1 for both 1C and 2C rates at 65 °C, respectively. The cyclic voltammetry analysis showed that the difference between the oxidation potential and the oxygen evolution potential of powder B is 122 mV. It indicated that Co could improve conductivity of electrons, restrict the oxygen evolution reaction and thus promote the high rate charge/discharge and high-temperature performance. Ca and Mg might effectively enhance the oxygen evolution potential in the charge process. Furthermore, the proper addition of Zn, Ca and Cu could lower the ionization energy and elevated the transition energy, and thus the transfer of electrons in electrode materials was accelerated and the electrochemical performance of nickel hydroxide electrode was improved. It was a promising way to improve the electrochemical performance of spherical nickel hydroxide for Ni–MH batteries.