Electrochemical investigation on nanoscale CoO as additive to the positive electrodes for Ni/MH rechargeable batteries

The addition of CoO to the positive electrodes of Ni/MH rechargeable batteries provides excellent performance in terms of specific capacity and mean discharge voltage. CoO increases remarkably the active material utilization due to the formation of CoOOH conductive network. In this paper, an extensive study is focused on the addition of nanoscale CoO to the positive electrodes for Ni/MH batteries in comparison with usual submicron CoO particles. The electrochemical impedance spectroscopy is performed to reveal the advantages of nanoscale CoO to the electrodes. The results indicate that both the ohmic resistance of the electrode and the impedance of the electrochemical reaction decreased in the case of adding nanoscale CoO. Further study by charge–discharge cycling shows that the electrodes with nanoscale CoO have higher discharge capacity and higher mean discharge voltage, and the batteries with such electrodes present enhanced high-rate discharge capability.